diff options
Diffstat (limited to 'src/pdkim')
| -rw-r--r-- | src/pdkim/Makefile | 19 | ||||
| -rw-r--r-- | src/pdkim/README | 9 | ||||
| -rw-r--r-- | src/pdkim/config.h | 4 | ||||
| -rw-r--r-- | src/pdkim/crypt_ver.h | 33 | ||||
| -rw-r--r-- | src/pdkim/pdkim.c | 2097 | ||||
| -rw-r--r-- | src/pdkim/pdkim.h | 369 | ||||
| -rw-r--r-- | src/pdkim/pdkim_hash.h | 38 | ||||
| -rw-r--r-- | src/pdkim/signing.c | 903 | ||||
| -rw-r--r-- | src/pdkim/signing.h | 97 |
9 files changed, 3569 insertions, 0 deletions
diff --git a/src/pdkim/Makefile b/src/pdkim/Makefile new file mode 100644 index 0000000..47f92ee --- /dev/null +++ b/src/pdkim/Makefile @@ -0,0 +1,19 @@ +# Make file for building the pdkim library. +# Copyright (c) The Exim Maintainers 1995 - 2018 + +OBJ = pdkim.o signing.o + +pdkim.a: $(OBJ) + @$(RM_COMMAND) -f pdkim.a + @echo "$(AR) pdkim.a" + $(FE)$(AR) pdkim.a $(OBJ) + $(RANLIB) $@ + +.SUFFIXES: .o .c +.c.o:; @echo "$(CC) $*.c" + $(FE)$(CC) -c $(CFLAGS) $(INCLUDE) -I. $*.c + +pdkim.o: $(HDRS) crypt_ver.h pdkim.h pdkim.c +signing.o: $(HDRS) crypt_ver.h signing.h signing.c + +# End diff --git a/src/pdkim/README b/src/pdkim/README new file mode 100644 index 0000000..953e86e --- /dev/null +++ b/src/pdkim/README @@ -0,0 +1,9 @@ +PDKIM - a RFC4871 (DKIM) implementation +http://duncanthrax.net/pdkim/ +Copyright (C) 2009 Tom Kistner <tom@duncanthrax.net> + +No longer includes code from the PolarSSL project. +Copyright (C) 2016 Jeremy Harris <jgh@exim.org> + +This copy of PDKIM is included with Exim. For a standalone distribution, +visit http://duncanthrax.net/pdkim/. diff --git a/src/pdkim/config.h b/src/pdkim/config.h new file mode 100644 index 0000000..fdd4cfe --- /dev/null +++ b/src/pdkim/config.h @@ -0,0 +1,4 @@ +#define POLARSSL_BASE64_C + + + diff --git a/src/pdkim/crypt_ver.h b/src/pdkim/crypt_ver.h new file mode 100644 index 0000000..a6d7e36 --- /dev/null +++ b/src/pdkim/crypt_ver.h @@ -0,0 +1,33 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) Jeremy Harris 1995 - 2018 */ +/* See the file NOTICE for conditions of use and distribution. */ + +/* Signing and hashing routine selection for PDKIM */ + +#include "../exim.h" +#include "../sha_ver.h" + + +#ifdef USE_GNUTLS +# include <gnutls/gnutls.h> + +# if GNUTLS_VERSION_NUMBER >= 0x030000 +# define SIGN_GNUTLS +# if GNUTLS_VERSION_NUMBER >= 0x030600 +# define SIGN_HAVE_ED25519 +# endif +# else +# define SIGN_GCRYPT +# endif +#endif + +#ifdef USE_OPENSSL +# define SIGN_OPENSSL +# if !defined(LIBRESSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x10101000L +# define SIGN_HAVE_ED25519 +# endif +#endif + diff --git a/src/pdkim/pdkim.c b/src/pdkim/pdkim.c new file mode 100644 index 0000000..e47bfc5 --- /dev/null +++ b/src/pdkim/pdkim.c @@ -0,0 +1,2097 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * + * Copyright (c) The Exim Maintainers 2021 - 2022 + * Copyright (C) 2009 - 2016 Tom Kistner <tom@duncanthrax.net> + * Copyright (C) 2016 - 2020 Jeremy Harris <jgh@exim.org> + * + * http://duncanthrax.net/pdkim/ + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include "../exim.h" + + +#ifndef DISABLE_DKIM /* entire file */ + +#ifdef DISABLE_TLS +# error Must not DISABLE_TLS, for DKIM +#endif + +#include "crypt_ver.h" + +#ifdef SIGN_OPENSSL +# include <openssl/rsa.h> +# include <openssl/ssl.h> +# include <openssl/err.h> +#elif defined(SIGN_GNUTLS) +# include <gnutls/gnutls.h> +# include <gnutls/x509.h> +#endif + +#include "pdkim.h" +#include "signing.h" + +#define PDKIM_SIGNATURE_VERSION "1" +#define PDKIM_PUB_RECORD_VERSION US "DKIM1" + +#define PDKIM_MAX_HEADER_LEN 65536 +#define PDKIM_MAX_HEADERS 512 +#define PDKIM_MAX_BODY_LINE_LEN 16384 +#define PDKIM_DNS_TXT_MAX_NAMELEN 1024 + +/* -------------------------------------------------------------------------- */ +struct pdkim_stringlist { + uschar * value; + int tag; + void * next; +}; + +/* -------------------------------------------------------------------------- */ +/* A bunch of list constants */ +const uschar * pdkim_querymethods[] = { + US"dns/txt", + NULL +}; +const uschar * pdkim_canons[] = { + US"simple", + US"relaxed", + NULL +}; + +const pdkim_hashtype pdkim_hashes[] = { + { US"sha1", HASH_SHA1 }, + { US"sha256", HASH_SHA2_256 }, + { US"sha512", HASH_SHA2_512 } +}; + +const uschar * pdkim_keytypes[] = { + [KEYTYPE_RSA] = US"rsa", +#ifdef SIGN_HAVE_ED25519 + [KEYTYPE_ED25519] = US"ed25519", /* Works for 3.6.0 GnuTLS, OpenSSL 1.1.1 */ +#endif + +#ifdef notyet_EC_dkim_extensions /* https://tools.ietf.org/html/draft-srose-dkim-ecc-00 */ + US"eccp256", + US"eccp348", + US"ed448", +#endif +}; + +typedef struct pdkim_combined_canon_entry { + const uschar * str; + int canon_headers; + int canon_body; +} pdkim_combined_canon_entry; + +pdkim_combined_canon_entry pdkim_combined_canons[] = { + { US"simple/simple", PDKIM_CANON_SIMPLE, PDKIM_CANON_SIMPLE }, + { US"simple/relaxed", PDKIM_CANON_SIMPLE, PDKIM_CANON_RELAXED }, + { US"relaxed/simple", PDKIM_CANON_RELAXED, PDKIM_CANON_SIMPLE }, + { US"relaxed/relaxed", PDKIM_CANON_RELAXED, PDKIM_CANON_RELAXED }, + { US"simple", PDKIM_CANON_SIMPLE, PDKIM_CANON_SIMPLE }, + { US"relaxed", PDKIM_CANON_RELAXED, PDKIM_CANON_SIMPLE }, + { NULL, 0, 0 } +}; + + +static const blob lineending = {.data = US"\r\n", .len = 2}; + +/* -------------------------------------------------------------------------- */ +uschar * +dkim_sig_to_a_tag(const pdkim_signature * sig) +{ +if ( sig->keytype < 0 || sig->keytype > nelem(pdkim_keytypes) + || sig->hashtype < 0 || sig->hashtype > nelem(pdkim_hashes)) + return US"err"; +return string_sprintf("%s-%s", + pdkim_keytypes[sig->keytype], pdkim_hashes[sig->hashtype].dkim_hashname); +} + + +static int +pdkim_keyname_to_keytype(const uschar * s) +{ +for (int i = 0; i < nelem(pdkim_keytypes); i++) + if (Ustrcmp(s, pdkim_keytypes[i]) == 0) return i; +return -1; +} + +int +pdkim_hashname_to_hashtype(const uschar * s, unsigned len) +{ +if (!len) len = Ustrlen(s); +for (int i = 0; i < nelem(pdkim_hashes); i++) + if (Ustrncmp(s, pdkim_hashes[i].dkim_hashname, len) == 0) + return i; +return -1; +} + +void +pdkim_cstring_to_canons(const uschar * s, unsigned len, + int * canon_head, int * canon_body) +{ +if (!len) len = Ustrlen(s); +for (int i = 0; pdkim_combined_canons[i].str; i++) + if ( Ustrncmp(s, pdkim_combined_canons[i].str, len) == 0 + && len == Ustrlen(pdkim_combined_canons[i].str)) + { + *canon_head = pdkim_combined_canons[i].canon_headers; + *canon_body = pdkim_combined_canons[i].canon_body; + break; + } +} + + + +const char * +pdkim_verify_status_str(int status) +{ +switch(status) + { + case PDKIM_VERIFY_NONE: return "PDKIM_VERIFY_NONE"; + case PDKIM_VERIFY_INVALID: return "PDKIM_VERIFY_INVALID"; + case PDKIM_VERIFY_FAIL: return "PDKIM_VERIFY_FAIL"; + case PDKIM_VERIFY_PASS: return "PDKIM_VERIFY_PASS"; + default: return "PDKIM_VERIFY_UNKNOWN"; + } +} + +const char * +pdkim_verify_ext_status_str(int ext_status) +{ +switch(ext_status) + { + case PDKIM_VERIFY_FAIL_BODY: return "PDKIM_VERIFY_FAIL_BODY"; + case PDKIM_VERIFY_FAIL_MESSAGE: return "PDKIM_VERIFY_FAIL_MESSAGE"; + case PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH: return "PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH"; + case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: return "PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE"; + case PDKIM_VERIFY_INVALID_BUFFER_SIZE: return "PDKIM_VERIFY_INVALID_BUFFER_SIZE"; + case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: return "PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD"; + case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return "PDKIM_VERIFY_INVALID_PUBKEY_IMPORT"; + case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: return "PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE"; + case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: return "PDKIM_VERIFY_INVALID_SIGNATURE_ERROR"; + case PDKIM_VERIFY_INVALID_DKIM_VERSION: return "PDKIM_VERIFY_INVALID_DKIM_VERSION"; + default: return "PDKIM_VERIFY_UNKNOWN"; + } +} + +const uschar * +pdkim_errstr(int status) +{ +switch(status) + { + case PDKIM_OK: return US"OK"; + case PDKIM_FAIL: return US"FAIL"; + case PDKIM_ERR_RSA_PRIVKEY: return US"PRIVKEY"; + case PDKIM_ERR_RSA_SIGNING: return US"SIGNING"; + case PDKIM_ERR_LONG_LINE: return US"LONG_LINE"; + case PDKIM_ERR_BUFFER_TOO_SMALL: return US"BUFFER_TOO_SMALL"; + case PDKIM_ERR_EXCESS_SIGS: return US"EXCESS_SIGS"; + case PDKIM_SIGN_PRIVKEY_WRAP: return US"PRIVKEY_WRAP"; + case PDKIM_SIGN_PRIVKEY_B64D: return US"PRIVKEY_B64D"; + default: return US"(unknown)"; + } +} + + +/* -------------------------------------------------------------------------- */ +/* Print debugging functions */ +void +pdkim_quoteprint(const uschar *data, int len) +{ +for (int i = 0; i < len; i++) + { + const int c = data[i]; + switch (c) + { + case ' ' : debug_printf("{SP}"); break; + case '\t': debug_printf("{TB}"); break; + case '\r': debug_printf("{CR}"); break; + case '\n': debug_printf("{LF}"); break; + case '{' : debug_printf("{BO}"); break; + case '}' : debug_printf("{BC}"); break; + default: + if ( (c < 32) || (c > 127) ) + debug_printf("{%02x}", c); + else + debug_printf("%c", c); + break; + } + } +debug_printf("\n"); +} + +void +pdkim_hexprint(const uschar *data, int len) +{ +if (data) for (int i = 0 ; i < len; i++) debug_printf("%02x", data[i]); +else debug_printf("<NULL>"); +debug_printf("\n"); +} + + + +static pdkim_stringlist * +pdkim_prepend_stringlist(pdkim_stringlist * base, const uschar * str) +{ +pdkim_stringlist * new_entry = store_get(sizeof(pdkim_stringlist), GET_UNTAINTED); + +memset(new_entry, 0, sizeof(pdkim_stringlist)); +new_entry->value = string_copy(str); +if (base) new_entry->next = base; +return new_entry; +} + + + +/* Trim whitespace fore & aft */ + +static void +pdkim_strtrim(gstring * str) +{ +uschar * p = str->s; +uschar * q; + +while (*p == '\t' || *p == ' ') /* dump the leading whitespace */ + { str->size--; str->ptr--; str->s++; } + +while ( str->ptr > 0 + && ((q = str->s + str->ptr - 1), (*q == '\t' || *q == ' ')) + ) + str->ptr--; /* dump trailing whitespace */ + +(void) string_from_gstring(str); +} + + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT void +pdkim_free_ctx(pdkim_ctx *ctx) +{ +} + + +/* -------------------------------------------------------------------------- */ +/* Matches the name of the passed raw "header" against + the passed colon-separated "tick", and invalidates + the entry in tick. Entries can be prefixed for multi- or over-signing, + in which case do not invalidate. + + Returns OK for a match, or fail-code +*/ + +static int +header_name_match(const uschar * header, uschar * tick) +{ +const uschar * ticklist = tick; +int sep = ':'; +BOOL multisign; +uschar * hname, * p, * ele; +uschar * hcolon = Ustrchr(header, ':'); /* Get header name */ + +if (!hcolon) + return PDKIM_FAIL; /* This isn't a header */ + +/* if we had strncmpic() we wouldn't need this copy */ +hname = string_copyn(header, hcolon-header); + +while (p = US ticklist, ele = string_nextinlist(&ticklist, &sep, NULL, 0)) + { + switch (*ele) + { + case '=': case '+': multisign = TRUE; ele++; break; + default: multisign = FALSE; break; + } + + if (strcmpic(ele, hname) == 0) + { + if (!multisign) + *p = '_'; /* Invalidate this header name instance in tick-off list */ + return PDKIM_OK; + } + } +return PDKIM_FAIL; +} + + +/* -------------------------------------------------------------------------- */ +/* Performs "relaxed" canonicalization of a header. */ + +uschar * +pdkim_relax_header_n(const uschar * header, int len, BOOL append_crlf) +{ +BOOL past_field_name = FALSE; +BOOL seen_wsp = FALSE; +uschar * relaxed = store_get(len+3, GET_TAINTED); +uschar * q = relaxed; + +for (const uschar * p = header; p - header < len; p++) + { + uschar c = *p; + + if (c == '\r' || c == '\n') /* Ignore CR & LF */ + continue; + if (c == '\t' || c == ' ') + { + if (seen_wsp) + continue; + c = ' '; /* Turns WSP into SP */ + seen_wsp = TRUE; + } + else + if (!past_field_name && c == ':') + { + if (seen_wsp) q--; /* This removes WSP immediately before the colon */ + seen_wsp = TRUE; /* This removes WSP immediately after the colon */ + past_field_name = TRUE; + } + else + seen_wsp = FALSE; + + /* Lowercase header name */ + if (!past_field_name) c = tolower(c); + *q++ = c; + } + +if (q > relaxed && q[-1] == ' ') q--; /* Squash eventual trailing SP */ + +if (append_crlf) { *q++ = '\r'; *q++ = '\n'; } +*q = '\0'; +return relaxed; +} + + +uschar * +pdkim_relax_header(const uschar * header, BOOL append_crlf) +{ +return pdkim_relax_header_n(header, Ustrlen(header), append_crlf); +} + + +/* -------------------------------------------------------------------------- */ +#define PDKIM_QP_ERROR_DECODE -1 + +static const uschar * +pdkim_decode_qp_char(const uschar *qp_p, int *c) +{ +const uschar *initial_pos = qp_p; + +/* Advance one char */ +qp_p++; + +/* Check for two hex digits and decode them */ +if (isxdigit(*qp_p) && isxdigit(qp_p[1])) + { + /* Do hex conversion */ + *c = (isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10) << 4; + *c |= isdigit(qp_p[1]) ? qp_p[1] - '0' : toupper(qp_p[1]) - 'A' + 10; + return qp_p + 2; + } + +/* Illegal char here */ +*c = PDKIM_QP_ERROR_DECODE; +return initial_pos; +} + + +/* -------------------------------------------------------------------------- */ + +static uschar * +pdkim_decode_qp(const uschar * str) +{ +int nchar = 0; +uschar * q; +const uschar * p = str; +uschar * n = store_get(Ustrlen(str)+1, GET_TAINTED); + +*n = '\0'; +q = n; +while (*p) + { + if (*p == '=') + { + p = pdkim_decode_qp_char(p, &nchar); + if (nchar >= 0) + { + *q++ = nchar; + continue; + } + } + else + *q++ = *p; + p++; + } +*q = '\0'; +return n; +} + + +/* -------------------------------------------------------------------------- */ + +void +pdkim_decode_base64(const uschar * str, blob * b) +{ +int dlen = b64decode(str, &b->data); +if (dlen < 0) b->data = NULL; +b->len = dlen; +} + +uschar * +pdkim_encode_base64(blob * b) +{ +return b64encode(CUS b->data, b->len); +} + + +/* -------------------------------------------------------------------------- */ +#define PDKIM_HDR_LIMBO 0 +#define PDKIM_HDR_TAG 1 +#define PDKIM_HDR_VALUE 2 + +static pdkim_signature * +pdkim_parse_sig_header(pdkim_ctx * ctx, uschar * raw_hdr) +{ +pdkim_signature * sig; +uschar *q; +gstring * cur_tag = NULL; +gstring * cur_val = NULL; +BOOL past_hname = FALSE; +BOOL in_b_val = FALSE; +int where = PDKIM_HDR_LIMBO; + +sig = store_get(sizeof(pdkim_signature), GET_UNTAINTED); +memset(sig, 0, sizeof(pdkim_signature)); +sig->bodylength = -1; + +/* Set so invalid/missing data error display is accurate */ +sig->version = 0; +sig->keytype = -1; +sig->hashtype = -1; + +q = sig->rawsig_no_b_val = store_get(Ustrlen(raw_hdr)+1, GET_TAINTED); + +for (uschar * p = raw_hdr; ; p++) + { + char c = *p; + + /* Ignore FWS */ + if (c == '\r' || c == '\n') + goto NEXT_CHAR; + + /* Fast-forward through header name */ + if (!past_hname) + { + if (c == ':') past_hname = TRUE; + goto NEXT_CHAR; + } + + if (where == PDKIM_HDR_LIMBO) + { + /* In limbo, just wait for a tag-char to appear */ + if (!(c >= 'a' && c <= 'z')) + goto NEXT_CHAR; + + where = PDKIM_HDR_TAG; + } + + if (where == PDKIM_HDR_TAG) + { + if (c >= 'a' && c <= 'z') + cur_tag = string_catn(cur_tag, p, 1); + + if (c == '=') + { + if (Ustrcmp(string_from_gstring(cur_tag), "b") == 0) + { + *q++ = '='; + in_b_val = TRUE; + } + where = PDKIM_HDR_VALUE; + goto NEXT_CHAR; + } + } + + if (where == PDKIM_HDR_VALUE) + { + if (c == '\r' || c == '\n' || c == ' ' || c == '\t') + goto NEXT_CHAR; + + if (c == ';' || c == '\0') + { + /* We must have both tag and value, and tags must be one char except + for the possibility of "bh". */ + + if ( cur_tag && cur_val + && (cur_tag->ptr == 1 || *cur_tag->s == 'b') + ) + { + (void) string_from_gstring(cur_val); + pdkim_strtrim(cur_val); + + DEBUG(D_acl) debug_printf(" %s=%s\n", cur_tag->s, cur_val->s); + + switch (*cur_tag->s) + { + case 'b': /* sig-data or body-hash */ + switch (cur_tag->s[1]) + { + case '\0': pdkim_decode_base64(cur_val->s, &sig->sighash); break; + case 'h': if (cur_tag->ptr == 2) + pdkim_decode_base64(cur_val->s, &sig->bodyhash); + break; + default: break; + } + break; + case 'v': /* version */ + /* We only support version 1, and that is currently the + only version there is. */ + sig->version = + Ustrcmp(cur_val->s, PDKIM_SIGNATURE_VERSION) == 0 ? 1 : -1; + break; + case 'a': /* algorithm */ + { + const uschar * list = cur_val->s; + int sep = '-'; + uschar * elem; + + if ((elem = string_nextinlist(&list, &sep, NULL, 0))) + sig->keytype = pdkim_keyname_to_keytype(elem); + if ((elem = string_nextinlist(&list, &sep, NULL, 0))) + for (int i = 0; i < nelem(pdkim_hashes); i++) + if (Ustrcmp(elem, pdkim_hashes[i].dkim_hashname) == 0) + { sig->hashtype = i; break; } + } + + case 'c': /* canonicalization */ + pdkim_cstring_to_canons(cur_val->s, 0, + &sig->canon_headers, &sig->canon_body); + break; + case 'q': /* Query method (for pubkey)*/ + for (int i = 0; pdkim_querymethods[i]; i++) + if (Ustrcmp(cur_val->s, pdkim_querymethods[i]) == 0) + { + sig->querymethod = i; /* we never actually use this */ + break; + } + break; + case 's': /* Selector */ + sig->selector = string_copyn(cur_val->s, cur_val->ptr); break; + case 'd': /* SDID */ + sig->domain = string_copyn(cur_val->s, cur_val->ptr); break; + case 'i': /* AUID */ + sig->identity = pdkim_decode_qp(cur_val->s); break; + case 't': /* Timestamp */ + sig->created = strtoul(CS cur_val->s, NULL, 10); break; + case 'x': /* Expiration */ + sig->expires = strtoul(CS cur_val->s, NULL, 10); break; + case 'l': /* Body length count */ + sig->bodylength = strtol(CS cur_val->s, NULL, 10); break; + case 'h': /* signed header fields */ + sig->headernames = string_copyn(cur_val->s, cur_val->ptr); break; + case 'z': /* Copied headfields */ + sig->copiedheaders = pdkim_decode_qp(cur_val->s); break; +/*XXX draft-ietf-dcrup-dkim-crypto-05 would need 'p' tag support +for rsafp signatures. But later discussion is dropping those. */ + default: + DEBUG(D_acl) debug_printf(" Unknown tag encountered\n"); + break; + } + } + cur_tag = cur_val = NULL; + in_b_val = FALSE; + where = PDKIM_HDR_LIMBO; + } + else + cur_val = string_catn(cur_val, p, 1); + } + +NEXT_CHAR: + if (c == '\0') + break; + + if (!in_b_val) + *q++ = c; + } + +if (sig->keytype < 0 || sig->hashtype < 0) /* Cannot verify this signature */ + return NULL; + +*q = '\0'; +/* Chomp raw header. The final newline must not be added to the signature. */ +while (--q > sig->rawsig_no_b_val && (*q == '\r' || *q == '\n')) + *q = '\0'; + +DEBUG(D_acl) + { + debug_printf( + "DKIM >> Raw signature w/o b= tag value >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + pdkim_quoteprint(US sig->rawsig_no_b_val, Ustrlen(sig->rawsig_no_b_val)); + debug_printf( + "DKIM >> Sig size: %4u bits\n", (unsigned) sig->sighash.len*8); + debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + +if (!pdkim_set_sig_bodyhash(ctx, sig)) + return NULL; + +return sig; +} + + +/* -------------------------------------------------------------------------- */ + +pdkim_pubkey * +pdkim_parse_pubkey_record(const uschar *raw_record) +{ +const uschar * ele; +int sep = ';'; +pdkim_pubkey * pub; + +pub = store_get(sizeof(pdkim_pubkey), GET_TAINTED); +memset(pub, 0, sizeof(pdkim_pubkey)); + +while ((ele = string_nextinlist(&raw_record, &sep, NULL, 0))) + { + const uschar * val; + + if ((val = Ustrchr(ele, '='))) + { + int taglen = val++ - ele; + + DEBUG(D_acl) debug_printf(" %.*s=%s\n", taglen, ele, val); + switch (ele[0]) + { + case 'v': pub->version = val; break; + case 'h': pub->hashes = val; break; + case 'k': pub->keytype = val; break; + case 'g': pub->granularity = val; break; + case 'n': pub->notes = pdkim_decode_qp(val); break; + case 'p': pdkim_decode_base64(val, &pub->key); break; + case 's': pub->srvtype = val; break; + case 't': if (Ustrchr(val, 'y')) pub->testing = 1; + if (Ustrchr(val, 's')) pub->no_subdomaining = 1; + break; + default: DEBUG(D_acl) debug_printf(" Unknown tag encountered\n"); break; + } + } + } + +/* Set fallback defaults */ +if (!pub->version) + pub->version = string_copy(PDKIM_PUB_RECORD_VERSION); +else if (Ustrcmp(pub->version, PDKIM_PUB_RECORD_VERSION) != 0) + { + DEBUG(D_acl) debug_printf(" Bad v= field\n"); + return NULL; + } + +if (!pub->granularity) pub->granularity = US"*"; +if (!pub->keytype ) pub->keytype = US"rsa"; +if (!pub->srvtype ) pub->srvtype = US"*"; + +/* p= is required */ +if (pub->key.data) + return pub; + +DEBUG(D_acl) debug_printf(" Missing p= field\n"); +return NULL; +} + + +/* -------------------------------------------------------------------------- */ + +/* Update one bodyhash with some additional data. +If we have to relax the data for this sig, return our copy of it. */ + +static blob * +pdkim_update_ctx_bodyhash(pdkim_bodyhash * b, const blob * orig_data, blob * relaxed_data) +{ +const blob * canon_data = orig_data; +size_t left; + +/* Defaults to simple canon (no further treatment necessary) */ + +if (b->canon_method == PDKIM_CANON_RELAXED) + { + /* Relax the line if not done already */ + if (!relaxed_data) + { + BOOL seen_wsp = FALSE; + int q = 0; + + /* We want to be able to free this else we allocate + for the entire message which could be many MB. Since + we don't know what allocations the SHA routines might + do, not safe to use store_get()/store_reset(). */ + + relaxed_data = store_malloc(sizeof(blob) + orig_data->len+1); + relaxed_data->data = US (relaxed_data+1); + + for (const uschar * p = orig_data->data, * r = p + orig_data->len; p < r; p++) + { + char c = *p; + if (c == '\r') + { + if (q > 0 && relaxed_data->data[q-1] == ' ') + q--; + } + else if (c == '\t' || c == ' ') + { + c = ' '; /* Turns WSP into SP */ + if (seen_wsp) + continue; + seen_wsp = TRUE; + } + else + seen_wsp = FALSE; + relaxed_data->data[q++] = c; + } + relaxed_data->data[q] = '\0'; + relaxed_data->len = q; + } + canon_data = relaxed_data; + } + +/* Make sure we don't exceed the to-be-signed body length */ +left = canon_data->len; +if ( b->bodylength >= 0 + && left > (unsigned long)b->bodylength - b->signed_body_bytes + ) + left = (unsigned long)b->bodylength - b->signed_body_bytes; + +if (left > 0) + { + exim_sha_update(&b->body_hash_ctx, CUS canon_data->data, left); + b->signed_body_bytes += left; + DEBUG(D_acl) pdkim_quoteprint(canon_data->data, left); + } + +return relaxed_data; +} + + +/* -------------------------------------------------------------------------- */ + +static void +pdkim_finish_bodyhash(pdkim_ctx * ctx) +{ +for (pdkim_bodyhash * b = ctx->bodyhash; b; b = b->next) /* Finish hashes */ + { + DEBUG(D_acl) debug_printf("DKIM: finish bodyhash %s/%s/%ld len %ld\n", + pdkim_hashes[b->hashtype].dkim_hashname, pdkim_canons[b->canon_method], + b->bodylength, b->signed_body_bytes); + exim_sha_finish(&b->body_hash_ctx, &b->bh); + } + +/* Traverse all signatures */ +for (pdkim_signature * sig = ctx->sig; sig; sig = sig->next) + { + pdkim_bodyhash * b = sig->calc_body_hash; + + DEBUG(D_acl) + { + debug_printf("DKIM [%s]%s Body bytes (%s) hashed: %lu\n" + "DKIM [%s]%s Body %s computed: ", + sig->domain, sig->selector, pdkim_canons[b->canon_method], b->signed_body_bytes, + sig->domain, sig->selector, pdkim_hashes[b->hashtype].dkim_hashname); + pdkim_hexprint(CUS b->bh.data, b->bh.len); + } + + /* SIGNING -------------------------------------------------------------- */ + if (ctx->flags & PDKIM_MODE_SIGN) + { + /* If bodylength limit is set, and we have received less bytes + than the requested amount, effectively remove the limit tag. */ + if (b->signed_body_bytes < sig->bodylength) + sig->bodylength = -1; + } + + else + /* VERIFICATION --------------------------------------------------------- */ + /* Be careful that the header sig included a bodyash */ + + if (sig->bodyhash.data && sig->bodyhash.len == b->bh.len + && memcmp(b->bh.data, sig->bodyhash.data, b->bh.len) == 0) + { + DEBUG(D_acl) debug_printf("DKIM [%s] Body hash compared OK\n", sig->domain); + } + else + { + DEBUG(D_acl) + { + debug_printf("DKIM [%s] Body hash signature from headers: ", sig->domain); + pdkim_hexprint(sig->bodyhash.data, sig->bodyhash.len); + debug_printf("DKIM [%s] Body hash did NOT verify\n", sig->domain); + } + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_FAIL_BODY; + } + } +} + + + +static void +pdkim_body_complete(pdkim_ctx * ctx) +{ +/* In simple body mode, if any empty lines were buffered, +replace with one. rfc 4871 3.4.3 */ +/*XXX checking the signed-body-bytes is a gross hack; I think +it indicates that all linebreaks should be buffered, including +the one terminating a text line */ + +for (pdkim_bodyhash * b = ctx->bodyhash; b; b = b->next) + if ( b->canon_method == PDKIM_CANON_SIMPLE + && b->signed_body_bytes == 0 + && b->num_buffered_blanklines > 0 + ) + (void) pdkim_update_ctx_bodyhash(b, &lineending, NULL); + +ctx->flags |= PDKIM_SEEN_EOD; +ctx->linebuf_offset = 0; +} + + + +/* -------------------------------------------------------------------------- */ +/* Call from pdkim_feed below for processing complete body lines */ +/* NOTE: the line is not NUL-terminated; but we have a count */ + +static void +pdkim_bodyline_complete(pdkim_ctx * ctx) +{ +blob line = {.data = ctx->linebuf, .len = ctx->linebuf_offset}; +blob * rnl = NULL; +blob * rline = NULL; + +/* Ignore extra data if we've seen the end-of-data marker */ +if (ctx->flags & PDKIM_SEEN_EOD) goto all_skip; + +/* We've always got one extra byte to stuff a zero ... */ +ctx->linebuf[line.len] = '\0'; + +/* Terminate on EOD marker */ +if (ctx->flags & PDKIM_DOT_TERM) + { + if (memcmp(line.data, ".\r\n", 3) == 0) + { pdkim_body_complete(ctx); return; } + + /* Unstuff dots */ + if (memcmp(line.data, "..", 2) == 0) + { line.data++; line.len--; } + } + +/* Empty lines need to be buffered until we find a non-empty line */ +if (memcmp(line.data, "\r\n", 2) == 0) + { + for (pdkim_bodyhash * b = ctx->bodyhash; b; b = b->next) + b->num_buffered_blanklines++; + goto all_skip; + } + +/* Process line for each bodyhash separately */ +for (pdkim_bodyhash * b = ctx->bodyhash; b; b = b->next) + { + if (b->canon_method == PDKIM_CANON_RELAXED) + { + /* Lines with just spaces need to be buffered too */ + uschar * cp = line.data; + char c; + + while ((c = *cp)) + { + if (c == '\r' && cp[1] == '\n') break; + if (c != ' ' && c != '\t') goto hash_process; + cp++; + } + + b->num_buffered_blanklines++; + goto hash_skip; + } + +hash_process: + /* At this point, we have a non-empty line, so release the buffered ones. */ + + while (b->num_buffered_blanklines) + { + rnl = pdkim_update_ctx_bodyhash(b, &lineending, rnl); + b->num_buffered_blanklines--; + } + + rline = pdkim_update_ctx_bodyhash(b, &line, rline); +hash_skip: ; + } + +if (rnl) store_free(rnl); +if (rline) store_free(rline); + +all_skip: + +ctx->linebuf_offset = 0; +return; +} + + +/* -------------------------------------------------------------------------- */ +/* Callback from pdkim_feed below for processing complete headers */ +#define DKIM_SIGNATURE_HEADERNAME "DKIM-Signature:" + +static int +pdkim_header_complete(pdkim_ctx * ctx) +{ +if ( (ctx->cur_header->ptr > 1) && + (ctx->cur_header->s[ctx->cur_header->ptr-1] == '\r') ) + --ctx->cur_header->ptr; +(void) string_from_gstring(ctx->cur_header); + +#ifdef EXPERIMENTAL_ARC +/* Feed the header line to ARC processing */ +(void) arc_header_feed(ctx->cur_header, !(ctx->flags & PDKIM_MODE_SIGN)); +#endif + +if (++ctx->num_headers > PDKIM_MAX_HEADERS) goto BAIL; + +/* SIGNING -------------------------------------------------------------- */ +if (ctx->flags & PDKIM_MODE_SIGN) + for (pdkim_signature * sig = ctx->sig; sig; sig = sig->next) /* Traverse all signatures */ + + /* Add header to the signed headers list (in reverse order) */ + sig->headers = pdkim_prepend_stringlist(sig->headers, ctx->cur_header->s); + +/* VERIFICATION ----------------------------------------------------------- */ +/* DKIM-Signature: headers are added to the verification list */ +else + { +#ifdef notdef + DEBUG(D_acl) + { + debug_printf("DKIM >> raw hdr: "); + pdkim_quoteprint(CUS ctx->cur_header->s, ctx->cur_header->ptr); + } +#endif + if (strncasecmp(CCS ctx->cur_header->s, + DKIM_SIGNATURE_HEADERNAME, + Ustrlen(DKIM_SIGNATURE_HEADERNAME)) == 0) + { + pdkim_signature * sig, * last_sig; + /* Create and chain new signature block. We could error-check for all + required tags here, but prefer to create the internal sig and expicitly + fail verification of it later. */ + + DEBUG(D_acl) debug_printf( + "DKIM >> Found sig, trying to parse >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + + sig = pdkim_parse_sig_header(ctx, ctx->cur_header->s); + + if (!(last_sig = ctx->sig)) + ctx->sig = sig; + else + { + while (last_sig->next) last_sig = last_sig->next; + last_sig->next = sig; + } + + if (dkim_collect_input && --dkim_collect_input == 0) + { + ctx->headers = pdkim_prepend_stringlist(ctx->headers, ctx->cur_header->s); + ctx->cur_header->s[ctx->cur_header->ptr = 0] = '\0'; + return PDKIM_ERR_EXCESS_SIGS; + } + } + + /* all headers are stored for signature verification */ + ctx->headers = pdkim_prepend_stringlist(ctx->headers, ctx->cur_header->s); + } + +BAIL: +ctx->cur_header->s[ctx->cur_header->ptr = 0] = '\0'; /* leave buffer for reuse */ +return PDKIM_OK; +} + + + +/* -------------------------------------------------------------------------- */ +#define HEADER_BUFFER_FRAG_SIZE 256 + +DLLEXPORT int +pdkim_feed(pdkim_ctx * ctx, uschar * data, int len) +{ +/* Alternate EOD signal, used in non-dotstuffing mode */ +if (!data) + pdkim_body_complete(ctx); + +else for (int p = 0; p < len; p++) + { + uschar c = data[p]; + int rc; + + if (ctx->flags & PDKIM_PAST_HDRS) + { + if (c == '\n' && !(ctx->flags & PDKIM_SEEN_CR)) /* emulate the CR */ + { + ctx->linebuf[ctx->linebuf_offset++] = '\r'; + if (ctx->linebuf_offset == PDKIM_MAX_BODY_LINE_LEN-1) + return PDKIM_ERR_LONG_LINE; + } + + /* Processing body byte */ + ctx->linebuf[ctx->linebuf_offset++] = c; + if (c == '\r') + ctx->flags |= PDKIM_SEEN_CR; + else if (c == '\n') + { + ctx->flags &= ~PDKIM_SEEN_CR; + pdkim_bodyline_complete(ctx); + } + + if (ctx->linebuf_offset == PDKIM_MAX_BODY_LINE_LEN-1) + return PDKIM_ERR_LONG_LINE; + } + else + { + /* Processing header byte */ + if (c == '\r') + ctx->flags |= PDKIM_SEEN_CR; + else if (c == '\n') + { + if (!(ctx->flags & PDKIM_SEEN_CR)) /* emulate the CR */ + ctx->cur_header = string_catn(ctx->cur_header, CUS "\r", 1); + + if (ctx->flags & PDKIM_SEEN_LF) /* Seen last header line */ + { + if ((rc = pdkim_header_complete(ctx)) != PDKIM_OK) + return rc; + + ctx->flags = (ctx->flags & ~(PDKIM_SEEN_LF|PDKIM_SEEN_CR)) | PDKIM_PAST_HDRS; + DEBUG(D_acl) debug_printf( + "DKIM >> Body data for hash, canonicalized >>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + continue; + } + else + ctx->flags = (ctx->flags & ~PDKIM_SEEN_CR) | PDKIM_SEEN_LF; + } + else if (ctx->flags & PDKIM_SEEN_LF) + { + if (!(c == '\t' || c == ' ')) /* End of header */ + if ((rc = pdkim_header_complete(ctx)) != PDKIM_OK) + return rc; + ctx->flags &= ~PDKIM_SEEN_LF; + } + + if (!ctx->cur_header || ctx->cur_header->ptr < PDKIM_MAX_HEADER_LEN) + ctx->cur_header = string_catn(ctx->cur_header, CUS &data[p], 1); + } + } +return PDKIM_OK; +} + + + +/* Extend a growing header with a continuation-linebreak */ +static gstring * +pdkim_hdr_cont(gstring * str, int * col) +{ +*col = 1; +return string_catn(str, US"\r\n\t", 3); +} + + + +/* + * RFC 5322 specifies that header line length SHOULD be no more than 78 + * pdkim_headcat + * + * Returns gstring (not nul-terminated) appending to one supplied + * + * col: this int holds and receives column number (octets since last '\n') + * str: partial string to append to + * pad: padding, split line or space after before or after eg: ";". + * Only the initial charater is used. + * intro: - must join to payload eg "h=", usually the tag name + * payload: eg base64 data - long data can be split arbitrarily. + * + * this code doesn't fold the header in some of the places that RFC4871 + * allows: As per RFC5322(2.2.3) it only folds before or after tag-value + * pairs and inside long values. it also always spaces or breaks after the + * "pad" + * + * No guarantees are made for output given out-of range input. like tag + * names longer than 78, or bogus col. Input is assumed to be free of line breaks. + */ + +static gstring * +pdkim_headcat(int * col, gstring * str, + const uschar * pad, const uschar * intro, const uschar * payload) +{ +int len, chomp, padded = 0; + +/* If we can fit at least the pad at the end of current line, do it now. +Otherwise, wrap if there is a pad. */ + +if (pad) + if (*col + 1 <= 78) + { + str = string_catn(str, pad, 1); + (*col)++; + pad = NULL; + padded = 1; + } + else + str = pdkim_hdr_cont(str, col); + +/* Special case: if the whole addition does not fit at the end of the current +line, but could fit on a new line, wrap to give it its full, dedicated line. */ + +len = (pad ? 2 : padded) + + (intro ? Ustrlen(intro) : 0) + + (payload ? Ustrlen(payload) : 0); +if (len <= 77 && *col+len > 78) + { + str = pdkim_hdr_cont(str, col); + padded = 0; + } + +/* Either we already dealt with the pad or we know there is room */ + +if (pad) + { + str = string_catn(str, pad, 1); + str = string_catn(str, US" ", 1); + *col += 2; + } +else if (padded && *col < 78) + { + str = string_catn(str, US" ", 1); + (*col)++; + } + +/* Call recursively with intro as payload: it gets the same, special treatment +(that is, not split if < 78). */ + +if (intro) + str = pdkim_headcat(col, str, NULL, NULL, intro); + +if (payload) + for (len = Ustrlen(payload); len; len -= chomp) + { + if (*col >= 78) + str = pdkim_hdr_cont(str, col); + chomp = *col+len > 78 ? 78 - *col : len; + str = string_catn(str, payload, chomp); + *col += chomp; + payload += chomp; + } + +return str; +} + + +/* -------------------------------------------------------------------------- */ + +/* Signing: create signature header +*/ +static uschar * +pdkim_create_header(pdkim_signature * sig, BOOL final) +{ +uschar * base64_bh; +uschar * base64_b; +int col = 0; +gstring * hdr; +gstring * canon_all; + +canon_all = string_cat (NULL, pdkim_canons[sig->canon_headers]); +canon_all = string_catn(canon_all, US"/", 1); +canon_all = string_cat (canon_all, pdkim_canons[sig->canon_body]); +(void) string_from_gstring(canon_all); + +hdr = string_cat(NULL, US"DKIM-Signature: v="PDKIM_SIGNATURE_VERSION); +col = hdr->ptr; + +/* Required and static bits */ +hdr = pdkim_headcat(&col, hdr, US";", US"a=", dkim_sig_to_a_tag(sig)); +hdr = pdkim_headcat(&col, hdr, US";", US"q=", pdkim_querymethods[sig->querymethod]); +hdr = pdkim_headcat(&col, hdr, US";", US"c=", canon_all->s); +hdr = pdkim_headcat(&col, hdr, US";", US"d=", sig->domain); +hdr = pdkim_headcat(&col, hdr, US";", US"s=", sig->selector); + +/* list of header names can be split between items. */ + { + uschar * n = string_copy(sig->headernames); + uschar * i = US"h="; + uschar * s = US";"; + + while (*n) + { + uschar * c = Ustrchr(n, ':'); + + if (c) *c ='\0'; + + if (!i) + hdr = pdkim_headcat(&col, hdr, NULL, NULL, US":"); + + hdr = pdkim_headcat(&col, hdr, s, i, n); + + if (!c) + break; + + n = c+1; + s = NULL; + i = NULL; + } + } + +base64_bh = pdkim_encode_base64(&sig->calc_body_hash->bh); +hdr = pdkim_headcat(&col, hdr, US";", US"bh=", base64_bh); + +/* Optional bits */ +if (sig->identity) + hdr = pdkim_headcat(&col, hdr, US";", US"i=", sig->identity); + +if (sig->created > 0) + { + uschar minibuf[21]; + + snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->created); + hdr = pdkim_headcat(&col, hdr, US";", US"t=", minibuf); +} + +if (sig->expires > 0) + { + uschar minibuf[21]; + + snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->expires); + hdr = pdkim_headcat(&col, hdr, US";", US"x=", minibuf); + } + +if (sig->bodylength >= 0) + { + uschar minibuf[21]; + + snprintf(CS minibuf, sizeof(minibuf), "%lu", sig->bodylength); + hdr = pdkim_headcat(&col, hdr, US";", US"l=", minibuf); + } + +/* Preliminary or final version? */ +if (final) + { + base64_b = pdkim_encode_base64(&sig->sighash); + hdr = pdkim_headcat(&col, hdr, US";", US"b=", base64_b); + + /* add trailing semicolon: I'm not sure if this is actually needed */ + hdr = pdkim_headcat(&col, hdr, NULL, US";", US""); + } +else + { + /* To satisfy the rule "all surrounding whitespace [...] deleted" + ( RFC 6376 section 3.7 ) we ensure there is no whitespace here. Otherwise + the headcat routine could insert a linebreak which the relaxer would reduce + to a single space preceding the terminating semicolon, resulting in an + incorrect header-hash. */ + hdr = pdkim_headcat(&col, hdr, US";", US"b=;", US""); + } + +return string_from_gstring(hdr); +} + + +/* -------------------------------------------------------------------------- */ + +/* According to draft-ietf-dcrup-dkim-crypto-07 "keys are 256 bits" (referring +to DNS, hence the pubkey). Check for more than 32 bytes; if so assume the +alternate possible representation (still) being discussed: a +SubjectPublickeyInfo wrapped key - and drop all but the trailing 32-bytes (it +should be a DER, with exactly 12 leading bytes - but we could accept a BER also, +which could be any size). We still rely on the crypto library for checking for +undersize. + +When the RFC is published this should be re-addressed. */ + +static void +check_bare_ed25519_pubkey(pdkim_pubkey * p) +{ +int excess = p->key.len - 32; +if (excess > 0) + { + DEBUG(D_acl) + debug_printf("DKIM: unexpected pubkey len %lu\n", (unsigned long) p->key.len); + p->key.data += excess; p->key.len = 32; + } +} + + +static pdkim_pubkey * +pdkim_key_from_dns(pdkim_ctx * ctx, pdkim_signature * sig, ev_ctx * vctx, + const uschar ** errstr) +{ +uschar * dns_txt_name, * dns_txt_reply; +pdkim_pubkey * p; + +/* Fetch public key for signing domain, from DNS */ + +dns_txt_name = string_sprintf("%s._domainkey.%s.", sig->selector, sig->domain); + +if ( !(dns_txt_reply = ctx->dns_txt_callback(dns_txt_name)) + || dns_txt_reply[0] == '\0' + ) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE; + return NULL; + } + +DEBUG(D_acl) + { + debug_printf( + "DKIM >> Parsing public key record >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n" + " %s\n" + " Raw record: ", + dns_txt_name); + pdkim_quoteprint(CUS dns_txt_reply, Ustrlen(dns_txt_reply)); + } + +if ( !(p = pdkim_parse_pubkey_record(CUS dns_txt_reply)) + || (Ustrcmp(p->srvtype, "*") != 0 && Ustrcmp(p->srvtype, "email") != 0) + ) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD; + + DEBUG(D_acl) + { + if (p) + debug_printf(" Invalid public key service type '%s'\n", p->srvtype); + else + debug_printf(" Error while parsing public key record\n"); + debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + return NULL; + } + +DEBUG(D_acl) debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + +/* Import public key */ + +/* Normally we use the signature a= tag to tell us the pubkey format. +When signing under debug we do a test-import of the pubkey, and at that +time we do not have a signature so we must interpret the pubkey k= tag +instead. Assume writing on the sig is ok in that case. */ + +if (sig->keytype < 0) + if ((sig->keytype = pdkim_keyname_to_keytype(p->keytype)) < 0) + { + DEBUG(D_acl) debug_printf("verify_init: unhandled keytype %s\n", p->keytype); + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_IMPORT; + return NULL; + } + +if (sig->keytype == KEYTYPE_ED25519) + check_bare_ed25519_pubkey(p); + +if ((*errstr = exim_dkim_verify_init(&p->key, + sig->keytype == KEYTYPE_ED25519 ? KEYFMT_ED25519_BARE : KEYFMT_DER, + vctx, &sig->keybits))) + { + DEBUG(D_acl) debug_printf("verify_init: %s\n", *errstr); + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_IMPORT; + return NULL; + } + +vctx->keytype = sig->keytype; +return p; +} + + +/* -------------------------------------------------------------------------- */ +/* Sort and filter the sigs developed from the message */ + +static pdkim_signature * +sort_sig_methods(pdkim_signature * siglist) +{ +pdkim_signature * yield, ** ss; +const uschar * prefs; +uschar * ele; +int sep; + +if (!siglist) return NULL; + +/* first select in order of hashtypes */ +DEBUG(D_acl) debug_printf("DKIM: dkim_verify_hashes '%s'\n", dkim_verify_hashes); +for (prefs = dkim_verify_hashes, sep = 0, yield = NULL, ss = &yield; + ele = string_nextinlist(&prefs, &sep, NULL, 0); ) + { + int i = pdkim_hashname_to_hashtype(CUS ele, 0); + for (pdkim_signature * s = siglist, * next, ** prev = &siglist; s; + s = next) + { + next = s->next; + if (s->hashtype == i) + { *prev = next; s->next = NULL; *ss = s; ss = &s->next; } + else + prev = &s->next; + } + } + +/* then in order of keytypes */ +siglist = yield; +DEBUG(D_acl) debug_printf("DKIM: dkim_verify_keytypes '%s'\n", dkim_verify_keytypes); +for (prefs = dkim_verify_keytypes, sep = 0, yield = NULL, ss = &yield; + ele = string_nextinlist(&prefs, &sep, NULL, 0); ) + { + int i = pdkim_keyname_to_keytype(CUS ele); + for (pdkim_signature * s = siglist, * next, ** prev = &siglist; s; + s = next) + { + next = s->next; + if (s->keytype == i) + { *prev = next; s->next = NULL; *ss = s; ss = &s->next; } + else + prev = &s->next; + } + } + +DEBUG(D_acl) for (pdkim_signature * s = yield; s; s = s->next) + debug_printf(" retain d=%s s=%s a=%s\n", + s->domain, s->selector, dkim_sig_to_a_tag(s)); +return yield; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT int +pdkim_feed_finish(pdkim_ctx * ctx, pdkim_signature ** return_signatures, + const uschar ** err) +{ +BOOL verify_pass = FALSE; + +/* Check if we must still flush a (partial) header. If that is the + case, the message has no body, and we must compute a body hash + out of '<CR><LF>' */ +if (ctx->cur_header && ctx->cur_header->ptr > 0) + { + blob * rnl = NULL; + int rc; + + if ((rc = pdkim_header_complete(ctx)) != PDKIM_OK) + return rc; + + for (pdkim_bodyhash * b = ctx->bodyhash; b; b = b->next) + rnl = pdkim_update_ctx_bodyhash(b, &lineending, rnl); + if (rnl) store_free(rnl); + } +else + DEBUG(D_acl) debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + +/* Build (and/or evaluate) body hash. Do this even if no DKIM sigs, in case we +have a hash to do for ARC. */ + +pdkim_finish_bodyhash(ctx); + +/* Sort and filter the recived signatures */ + +if (!(ctx->flags & PDKIM_MODE_SIGN)) + ctx->sig = sort_sig_methods(ctx->sig); + +if (!ctx->sig) + { + DEBUG(D_acl) debug_printf("DKIM: no signatures\n"); + *return_signatures = NULL; + return PDKIM_OK; + } + +for (pdkim_signature * sig = ctx->sig; sig; sig = sig->next) + { + hctx hhash_ctx; + uschar * sig_hdr = US""; + blob hhash; + gstring * hdata = NULL; + es_ctx sctx; + + if ( !(ctx->flags & PDKIM_MODE_SIGN) + && sig->verify_status == PDKIM_VERIFY_FAIL) + { + DEBUG(D_acl) + debug_printf("DKIM: [%s] abandoning this signature\n", sig->domain); + continue; + } + + /*XXX The hash of the headers is needed for GCrypt (for which we can do RSA + signing only, as it happens) and for either GnuTLS and OpenSSL when we are + signing with EC (specifically, Ed25519). The former is because the GCrypt + signing operation is pure (does not do its own hash) so we must hash. The + latter is because we (stupidly, but this is what the IETF draft is saying) + must hash with the declared hash method, then pass the result to the library + hash-and-sign routine (because that's all the libraries are providing. And + we're stuck with whatever that hidden hash method is, too). We may as well + do this hash incrementally. + We don't need the hash we're calculating here for the GnuTLS and OpenSSL + cases of RSA signing, since those library routines can do hash-and-sign. + + Some time in the future we could easily avoid doing the hash here for those + cases (which will be common for a long while. We could also change from + the current copy-all-the-headers-into-one-block, then call the hash-and-sign + implementation - to a proper incremental one. Unfortunately, GnuTLS just + cannot do incremental - either signing or verification. Unsure about GCrypt. + */ + + /*XXX The header hash is also used (so far) by the verify operation */ + + if (!exim_sha_init(&hhash_ctx, pdkim_hashes[sig->hashtype].exim_hashmethod)) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "DKIM: hash setup error, possibly nonhandled hashtype"); + break; + } + + if (ctx->flags & PDKIM_MODE_SIGN) + DEBUG(D_acl) debug_printf( + "DKIM >> Headers to be signed: >>>>>>>>>>>>\n" + " %s\n", + sig->sign_headers); + + DEBUG(D_acl) debug_printf( + "DKIM >> Header data for hash, canonicalized (%-7s), in sequence >>\n", + pdkim_canons[sig->canon_headers]); + + + /* SIGNING ---------------------------------------------------------------- */ + /* When signing, walk through our header list and add them to the hash. As we + go, construct a list of the header's names to use for the h= parameter. + Then append to that list any remaining header names for which there was no + header to sign. */ + + if (ctx->flags & PDKIM_MODE_SIGN) + { + gstring * g = NULL; + const uschar * l; + uschar * s; + int sep = 0; + + /* Import private key, including the keytype which we need for building + the signature header */ + + if ((*err = exim_dkim_signing_init(CUS sig->privkey, &sctx))) + { + log_write(0, LOG_MAIN|LOG_PANIC, "signing_init: %s", *err); + return PDKIM_ERR_RSA_PRIVKEY; + } + sig->keytype = sctx.keytype; + + sig->headernames = NULL; /* Collected signed header names */ + for (pdkim_stringlist * p = sig->headers; p; p = p->next) + { + uschar * rh = p->value; + + if (header_name_match(rh, sig->sign_headers) == PDKIM_OK) + { + /* Collect header names (Note: colon presence is guaranteed here) */ + g = string_append_listele_n(g, ':', rh, Ustrchr(rh, ':') - rh); + + if (sig->canon_headers == PDKIM_CANON_RELAXED) + rh = pdkim_relax_header(rh, TRUE); /* cook header for relaxed canon */ + + /* Feed header to the hash algorithm */ + exim_sha_update_string(&hhash_ctx, CUS rh); + + /* Remember headers block for signing (when the library cannot do incremental) */ + /*XXX we could avoid doing this for all but the GnuTLS/RSA case */ + hdata = exim_dkim_data_append(hdata, rh); + + DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh)); + } + } + + /* Any headers we wanted to sign but were not present must also be listed. + Ignore elements that have been ticked-off or are marked as never-oversign. */ + + l = sig->sign_headers; + while((s = string_nextinlist(&l, &sep, NULL, 0))) + { + if (*s == '+') /* skip oversigning marker */ + s++; + if (*s != '_' && *s != '=') + g = string_append_listele(g, ':', s); + } + sig->headernames = string_from_gstring(g); + + /* Create signature header with b= omitted */ + sig_hdr = pdkim_create_header(sig, FALSE); + } + + /* VERIFICATION ----------------------------------------------------------- */ + /* When verifying, walk through the header name list in the h= parameter and + add the headers to the hash in that order. */ + else + { + uschar * p = sig->headernames; + uschar * q; + + if (p) + { + /* clear tags */ + for (pdkim_stringlist * hdrs = ctx->headers; hdrs; hdrs = hdrs->next) + hdrs->tag = 0; + + p = string_copy(p); + while(1) + { + if ((q = Ustrchr(p, ':'))) + *q = '\0'; + + /*XXX walk the list of headers in same order as received. */ + for (pdkim_stringlist * hdrs = ctx->headers; hdrs; hdrs = hdrs->next) + if ( hdrs->tag == 0 + && strncasecmp(CCS hdrs->value, CCS p, Ustrlen(p)) == 0 + && (hdrs->value)[Ustrlen(p)] == ':' + ) + { + /* cook header for relaxed canon, or just copy it for simple */ + + uschar * rh = sig->canon_headers == PDKIM_CANON_RELAXED + ? pdkim_relax_header(hdrs->value, TRUE) + : string_copy(CUS hdrs->value); + + /* Feed header to the hash algorithm */ + exim_sha_update_string(&hhash_ctx, CUS rh); + + DEBUG(D_acl) pdkim_quoteprint(rh, Ustrlen(rh)); + hdrs->tag = 1; + break; + } + + if (!q) break; + p = q+1; + } + + sig_hdr = string_copy(sig->rawsig_no_b_val); + } + } + + DEBUG(D_acl) debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + + DEBUG(D_acl) + { + debug_printf( + "DKIM >> Signed DKIM-Signature header, pre-canonicalized >>>>>>>>>>>>>\n"); + pdkim_quoteprint(CUS sig_hdr, Ustrlen(sig_hdr)); + debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + + /* Relax header if necessary */ + if (sig->canon_headers == PDKIM_CANON_RELAXED) + sig_hdr = pdkim_relax_header(sig_hdr, FALSE); + + DEBUG(D_acl) + { + debug_printf("DKIM >> Signed DKIM-Signature header, canonicalized (%-7s) >>>>>>>\n", + pdkim_canons[sig->canon_headers]); + pdkim_quoteprint(CUS sig_hdr, Ustrlen(sig_hdr)); + debug_printf( + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } + + /* Finalize header hash */ + exim_sha_update_string(&hhash_ctx, CUS sig_hdr); + exim_sha_finish(&hhash_ctx, &hhash); + + DEBUG(D_acl) + { + debug_printf("DKIM [%s] Header %s computed: ", + sig->domain, pdkim_hashes[sig->hashtype].dkim_hashname); + pdkim_hexprint(hhash.data, hhash.len); + } + + /* Remember headers block for signing (when the signing library cannot do + incremental) */ + if (ctx->flags & PDKIM_MODE_SIGN) + hdata = exim_dkim_data_append(hdata, US sig_hdr); + + /* SIGNING ---------------------------------------------------------------- */ + if (ctx->flags & PDKIM_MODE_SIGN) + { + hashmethod hm = sig->keytype == KEYTYPE_ED25519 +#if defined(SIGN_OPENSSL) + ? HASH_NULL +#else + ? HASH_SHA2_512 +#endif + : pdkim_hashes[sig->hashtype].exim_hashmethod; + +#ifdef SIGN_HAVE_ED25519 + /* For GCrypt, and for EC, we pass the hash-of-headers to the signing + routine. For anything else we just pass the headers. */ + + if (sig->keytype != KEYTYPE_ED25519) +#endif + { + hhash.data = hdata->s; + hhash.len = hdata->ptr; + } + + if ((*err = exim_dkim_sign(&sctx, hm, &hhash, &sig->sighash))) + { + log_write(0, LOG_MAIN|LOG_PANIC, "signing: %s", *err); + return PDKIM_ERR_RSA_SIGNING; + } + + DEBUG(D_acl) + { + debug_printf( "DKIM [%s] b computed: ", sig->domain); + pdkim_hexprint(sig->sighash.data, sig->sighash.len); + } + + sig->signature_header = pdkim_create_header(sig, TRUE); + } + + /* VERIFICATION ----------------------------------------------------------- */ + else + { + ev_ctx vctx; + hashmethod hm; + + /* Make sure we have all required signature tags */ + if (!( sig->domain && *sig->domain + && sig->selector && *sig->selector + && sig->headernames && *sig->headernames + && sig->bodyhash.data + && sig->sighash.data + && sig->keytype >= 0 + && sig->hashtype >= 0 + && sig->version + ) ) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_SIGNATURE_ERROR; + + DEBUG(D_acl) debug_printf( + " Error in DKIM-Signature header: tags missing or invalid (%s)\n" + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n", + !(sig->domain && *sig->domain) ? "d=" + : !(sig->selector && *sig->selector) ? "s=" + : !(sig->headernames && *sig->headernames) ? "h=" + : !sig->bodyhash.data ? "bh=" + : !sig->sighash.data ? "b=" + : sig->keytype < 0 || sig->hashtype < 0 ? "a=" + : "v=" + ); + goto NEXT_VERIFY; + } + + /* Make sure sig uses supported DKIM version (only v1) */ + if (sig->version != 1) + { + sig->verify_status = PDKIM_VERIFY_INVALID; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_DKIM_VERSION; + + DEBUG(D_acl) debug_printf( + " Error in DKIM-Signature header: unsupported DKIM version\n" + "DKIM <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + goto NEXT_VERIFY; + } + + DEBUG(D_acl) + { + debug_printf( "DKIM [%s] b from mail: ", sig->domain); + pdkim_hexprint(sig->sighash.data, sig->sighash.len); + } + + if (!(sig->pubkey = pdkim_key_from_dns(ctx, sig, &vctx, err))) + { + log_write(0, LOG_MAIN, "DKIM: %s%s %s%s [failed key import]", + sig->domain ? "d=" : "", sig->domain ? sig->domain : US"", + sig->selector ? "s=" : "", sig->selector ? sig->selector : US""); + goto NEXT_VERIFY; + } + + /* If the pubkey limits to a list of specific hashes, ignore sigs that + do not have the hash part of the sig algorithm matching */ + + if (sig->pubkey->hashes) + { + const uschar * list = sig->pubkey->hashes, * ele; + int sep = ':'; + while ((ele = string_nextinlist(&list, &sep, NULL, 0))) + if (Ustrcmp(ele, pdkim_hashes[sig->hashtype].dkim_hashname) == 0) break; + if (!ele) + { + DEBUG(D_acl) debug_printf("pubkey h=%s vs. sig a=%s_%s\n", + sig->pubkey->hashes, + pdkim_keytypes[sig->keytype], + pdkim_hashes[sig->hashtype].dkim_hashname); + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH; + goto NEXT_VERIFY; + } + } + + hm = sig->keytype == KEYTYPE_ED25519 +#if defined(SIGN_OPENSSL) + ? HASH_NULL +#else + ? HASH_SHA2_512 +#endif + : pdkim_hashes[sig->hashtype].exim_hashmethod; + + /* Check the signature */ + + if ((*err = exim_dkim_verify(&vctx, hm, &hhash, &sig->sighash))) + { + DEBUG(D_acl) debug_printf("headers verify: %s\n", *err); + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_FAIL_MESSAGE; + goto NEXT_VERIFY; + } + if (*dkim_verify_min_keysizes) + { + unsigned minbits; + uschar * ss = expand_getkeyed(US pdkim_keytypes[sig->keytype], + dkim_verify_min_keysizes); + if (ss && (minbits = atoi(CS ss)) > sig->keybits) + { + DEBUG(D_acl) debug_printf("Key too short: Actual: %s %u Minima '%s'\n", + pdkim_keytypes[sig->keytype], sig->keybits, dkim_verify_min_keysizes); + sig->verify_status = PDKIM_VERIFY_FAIL; + sig->verify_ext_status = PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE; + } + } + + + /* We have a winner! (if bodyhash was correct earlier) */ + if (sig->verify_status == PDKIM_VERIFY_NONE) + { + sig->verify_status = PDKIM_VERIFY_PASS; + verify_pass = TRUE; + if (dkim_verify_minimal) break; + } + +NEXT_VERIFY: + + DEBUG(D_acl) + { + debug_printf("DKIM [%s] %s signature status: %s", + sig->domain, dkim_sig_to_a_tag(sig), + pdkim_verify_status_str(sig->verify_status)); + if (sig->verify_ext_status > 0) + debug_printf(" (%s)\n", + pdkim_verify_ext_status_str(sig->verify_ext_status)); + else + debug_printf("\n"); + } + } + } + +/* If requested, set return pointer to signature(s) */ +if (return_signatures) + *return_signatures = ctx->sig; + +return ctx->flags & PDKIM_MODE_SIGN || verify_pass + ? PDKIM_OK : PDKIM_FAIL; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT pdkim_ctx * +pdkim_init_verify(uschar * (*dns_txt_callback)(const uschar *), BOOL dot_stuffing) +{ +pdkim_ctx * ctx; + +ctx = store_get(sizeof(pdkim_ctx), GET_UNTAINTED); +memset(ctx, 0, sizeof(pdkim_ctx)); + +if (dot_stuffing) ctx->flags = PDKIM_DOT_TERM; +/* The line-buffer is for message data, hence tainted */ +ctx->linebuf = store_get(PDKIM_MAX_BODY_LINE_LEN, GET_TAINTED); +ctx->dns_txt_callback = dns_txt_callback; +ctx->cur_header = string_get_tainted(36, GET_TAINTED); + +return ctx; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT pdkim_signature * +pdkim_init_sign(pdkim_ctx * ctx, + uschar * domain, uschar * selector, uschar * privkey, + uschar * hashname, const uschar ** errstr) +{ +int hashtype; +pdkim_signature * sig; + +if (!domain || !selector || !privkey) + return NULL; + +/* Allocate & init one signature struct */ + +sig = store_get(sizeof(pdkim_signature), GET_UNTAINTED); +memset(sig, 0, sizeof(pdkim_signature)); + +sig->bodylength = -1; + +sig->domain = string_copy(US domain); +sig->selector = string_copy(US selector); +sig->privkey = string_copy(US privkey); +sig->keytype = -1; + +for (hashtype = 0; hashtype < nelem(pdkim_hashes); hashtype++) + if (Ustrcmp(hashname, pdkim_hashes[hashtype].dkim_hashname) == 0) + { sig->hashtype = hashtype; break; } +if (hashtype >= nelem(pdkim_hashes)) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "DKIM: unrecognised hashname '%s'", hashname); + return NULL; + } + +DEBUG(D_acl) + { + pdkim_signature s = *sig; + ev_ctx vctx; + + debug_printf("DKIM (checking verify key)>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n"); + if (!pdkim_key_from_dns(ctx, &s, &vctx, errstr)) + debug_printf("WARNING: bad dkim key in dns\n"); + debug_printf("DKIM (finished checking verify key)<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n"); + } +return sig; +} + + +/* -------------------------------------------------------------------------- */ + +DLLEXPORT void +pdkim_set_optional(pdkim_signature * sig, + char * sign_headers, + char * identity, + int canon_headers, + int canon_body, + long bodylength, + unsigned long created, + unsigned long expires) +{ +if (identity) + sig->identity = string_copy(US identity); + +sig->sign_headers = string_copy(sign_headers + ? US sign_headers : US PDKIM_DEFAULT_SIGN_HEADERS); + +sig->canon_headers = canon_headers; +sig->canon_body = canon_body; +sig->bodylength = bodylength; +sig->created = created; +sig->expires = expires; + +return; +} + + + +/* Set up a blob for calculating the bodyhash according to the +given needs. Use an existing one if possible, or create a new one. + +Return: hashblob pointer, or NULL on error +*/ +pdkim_bodyhash * +pdkim_set_bodyhash(pdkim_ctx * ctx, int hashtype, int canon_method, + long bodylength) +{ +pdkim_bodyhash * b; + +if (hashtype == -1 || canon_method == -1) return NULL; + +for (b = ctx->bodyhash; b; b = b->next) + if ( hashtype == b->hashtype + && canon_method == b->canon_method + && bodylength == b->bodylength) + { + DEBUG(D_receive) debug_printf("DKIM: using existing bodyhash %s/%s/%ld\n", + pdkim_hashes[hashtype].dkim_hashname, pdkim_canons[canon_method], bodylength); + return b; + } + +DEBUG(D_receive) debug_printf("DKIM: new bodyhash %s/%s/%ld\n", + pdkim_hashes[hashtype].dkim_hashname, pdkim_canons[canon_method], bodylength); +b = store_get(sizeof(pdkim_bodyhash), GET_UNTAINTED); +b->next = ctx->bodyhash; +b->hashtype = hashtype; +b->canon_method = canon_method; +b->bodylength = bodylength; +if (!exim_sha_init(&b->body_hash_ctx, /*XXX hash method: extend for sha512 */ + pdkim_hashes[hashtype].exim_hashmethod)) + { + DEBUG(D_acl) + debug_printf("DKIM: hash init error, possibly nonhandled hashtype\n"); + return NULL; + } +b->signed_body_bytes = 0; +b->num_buffered_blanklines = 0; +ctx->bodyhash = b; +return b; +} + + +/* Set up a blob for calculating the bodyhash according to the +needs of this signature. Use an existing one if possible, or +create a new one. + +Return: hashblob pointer, or NULL on error (only used as a boolean). +*/ +pdkim_bodyhash * +pdkim_set_sig_bodyhash(pdkim_ctx * ctx, pdkim_signature * sig) +{ +pdkim_bodyhash * b = pdkim_set_bodyhash(ctx, + sig->hashtype, sig->canon_body, sig->bodylength); +sig->calc_body_hash = b; +return b; +} + + +/* -------------------------------------------------------------------------- */ + + +void +pdkim_init_context(pdkim_ctx * ctx, BOOL dot_stuffed, + uschar * (*dns_txt_callback)(const uschar *)) +{ +memset(ctx, 0, sizeof(pdkim_ctx)); +ctx->flags = dot_stuffed ? PDKIM_MODE_SIGN | PDKIM_DOT_TERM : PDKIM_MODE_SIGN; +/* The line buffer is for message data, hence tainted */ +ctx->linebuf = store_get(PDKIM_MAX_BODY_LINE_LEN, GET_TAINTED); +DEBUG(D_acl) ctx->dns_txt_callback = dns_txt_callback; +} + + +void +pdkim_init(void) +{ +exim_dkim_init(); +} + + + +#endif /*DISABLE_DKIM*/ diff --git a/src/pdkim/pdkim.h b/src/pdkim/pdkim.h new file mode 100644 index 0000000..f6ff782 --- /dev/null +++ b/src/pdkim/pdkim.h @@ -0,0 +1,369 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * + * Copyright (C) 2009 - 2012 Tom Kistner <tom@duncanthrax.net> + * Copyright (c) 2016 - 2020 Jeremy Harris + * + * http://duncanthrax.net/pdkim/ + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ +#ifndef PDKIM_H +#define PDKIM_H + +#include "../blob.h" +#include "../hash.h" + +#define PDKIM_DEFAULT_SIGN_HEADERS "From:Sender:Reply-To:Subject:Date:"\ + "Message-ID:To:Cc:MIME-Version:Content-Type:"\ + "Content-Transfer-Encoding:Content-ID:"\ + "Content-Description:Resent-Date:Resent-From:"\ + "Resent-Sender:Resent-To:Resent-Cc:"\ + "Resent-Message-ID:In-Reply-To:References:"\ + "List-Id:List-Help:List-Unsubscribe:"\ + "List-Subscribe:List-Post:List-Owner:List-Archive" + +#define PDKIM_OVERSIGN_HEADERS "+From:+Sender:+Reply-To:+Subject:+Date:"\ + "+Message-ID:+To:+Cc:+MIME-Version:+Content-Type:"\ + "+Content-Transfer-Encoding:+Content-ID:"\ + "+Content-Description:+Resent-Date:+Resent-From:"\ + "+Resent-Sender:+Resent-To:+Resent-Cc:"\ + "+Resent-Message-ID:+In-Reply-To:+References:"\ + "+List-Id:+List-Help:+List-Unsubscribe:"\ + "+List-Subscribe:+List-Post:+List-Owner:+List-Archive" + +/* -------------------------------------------------------------------------- */ +/* Length of the preallocated buffer for the "answer" from the dns/txt + callback function. This should match the maximum RDLENGTH from DNS. */ +#define PDKIM_DNS_TXT_MAX_RECLEN (1 << 16) + +/* -------------------------------------------------------------------------- */ +/* Function success / error codes */ +#define PDKIM_OK 0 +#define PDKIM_FAIL -1 +#define PDKIM_ERR_RSA_PRIVKEY -101 +#define PDKIM_ERR_RSA_SIGNING -102 +#define PDKIM_ERR_LONG_LINE -103 +#define PDKIM_ERR_BUFFER_TOO_SMALL -104 +#define PDKIM_ERR_EXCESS_SIGS -105 +#define PDKIM_SIGN_PRIVKEY_WRAP -106 +#define PDKIM_SIGN_PRIVKEY_B64D -107 + +/* -------------------------------------------------------------------------- */ +/* Main/Extended verification status */ +#define PDKIM_VERIFY_NONE 0 +#define PDKIM_VERIFY_INVALID 1 +#define PDKIM_VERIFY_FAIL 2 +#define PDKIM_VERIFY_PASS 3 +#define PDKIM_VERIFY_POLICY BIT(31) + +#define PDKIM_VERIFY_FAIL_BODY 1 +#define PDKIM_VERIFY_FAIL_MESSAGE 2 +#define PDKIM_VERIFY_FAIL_SIG_ALGO_MISMATCH 3 +#define PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE 4 +#define PDKIM_VERIFY_INVALID_BUFFER_SIZE 5 +#define PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD 6 +#define PDKIM_VERIFY_INVALID_PUBKEY_IMPORT 7 +#define PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE 8 +#define PDKIM_VERIFY_INVALID_SIGNATURE_ERROR 9 +#define PDKIM_VERIFY_INVALID_DKIM_VERSION 10 + +/* -------------------------------------------------------------------------- */ +/* Some parameter values */ +#define PDKIM_QUERYMETHOD_DNS_TXT 0 + +#define PDKIM_CANON_SIMPLE 0 +#define PDKIM_CANON_RELAXED 1 + +/* -------------------------------------------------------------------------- */ +/* Some required forward declarations, please ignore */ +typedef struct pdkim_stringlist pdkim_stringlist; +typedef struct pdkim_str pdkim_str; +typedef struct sha1_context sha1_context; +typedef struct sha2_context sha2_context; +#define HAVE_SHA1_CONTEXT +#define HAVE_SHA2_CONTEXT + +/* -------------------------------------------------------------------------- */ +/* Some concessions towards Redmond */ +#ifdef WINDOWS +#define snprintf _snprintf +#define strcasecmp _stricmp +#define strncasecmp _strnicmp +#define DLLEXPORT __declspec(dllexport) +#else +#define DLLEXPORT +#endif + + +/* -------------------------------------------------------------------------- */ +/* Public key as (usually) fetched from DNS */ +typedef struct pdkim_pubkey { + const uschar * version; /* v= */ + const uschar *granularity; /* g= */ + + const uschar * hashes; /* h= */ + const uschar * keytype; /* k= */ + const uschar * srvtype; /* s= */ + uschar *notes; /* n= */ + + blob key; /* p= */ + int testing; /* t=y */ + int no_subdomaining; /* t=s */ +} pdkim_pubkey; + +/* -------------------------------------------------------------------------- */ +/* Body-hash to be calculated */ +typedef struct pdkim_bodyhash { + struct pdkim_bodyhash * next; + int hashtype; + int canon_method; + long bodylength; + + hctx body_hash_ctx; + unsigned long signed_body_bytes; /* done so far */ + int num_buffered_blanklines; + + blob bh; /* completed hash */ +} pdkim_bodyhash; + +/* -------------------------------------------------------------------------- */ +/* Signature as it appears in a DKIM-Signature header */ +typedef struct pdkim_signature { + struct pdkim_signature * next; + + /* Bits stored in a DKIM signature header --------------------------- */ + + /* (v=) The version, as an integer. Currently, always "1" */ + int version; + + /* (a=) The signature algorithm. */ + int keytype; /* pdkim_keytypes index */ + unsigned keybits; /* size of the key */ + int hashtype; /* pdkim_hashes index */ + + /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE + or PDKIM_CANON_RELAXED */ + int canon_headers; + + /* (c=/x) Body canonicalization method. Either PDKIM_CANON_SIMPLE + or PDKIM_CANON_RELAXED */ + int canon_body; + + /* (q=) Query Method. Currently, only PDKIM_QUERYMETHOD_DNS_TXT + is specified */ + int querymethod; + + /* (s=) The selector string as given in the signature */ + uschar *selector; + + /* (d=) The domain as given in the signature */ + uschar *domain; + + /* (i=) The identity as given in the signature */ + uschar *identity; + + /* (t=) Timestamp of signature creation */ + unsigned long created; + + /* (x=) Timestamp of expiry of signature */ + unsigned long expires; + + /* (l=) Amount of hashed body bytes (after canonicalization). Default + is -1. Note: a value of 0 means that the body is unsigned! */ + long bodylength; + + /* (h=) Colon-separated list of header names that are included in the + signature */ + uschar *headernames; + + /* (z=) */ + uschar *copiedheaders; + + /* (b=) Raw signature data, along with its length in bytes */ + blob sighash; + + /* (bh=) Raw body hash data, along with its length in bytes */ + blob bodyhash; + + /* Folded DKIM-Signature: header. Signing only, NULL for verifying. + Ready for insertion into the message. Note: Folded using CRLFTB, + but final line terminator is NOT included. Note2: This buffer is + free()d when you call pdkim_free_ctx(). */ + uschar *signature_header; + + /* The main verification status. Verification only. One of: + + PDKIM_VERIFY_NONE Verification was not attempted. This status + should not appear. + + PDKIM_VERIFY_INVALID There was an error while trying to verify + the signature. A more precise description + is available in verify_ext_status. + + PDKIM_VERIFY_FAIL Verification failed because either the body + hash did not match, or the signature verification + failed. This means the message was modified. + Check verify_ext_status for the exact reason. + + PDKIM_VERIFY_PASS Verification succeeded. + */ + int verify_status; + + /* Extended verification status. Verification only. Depending on the value + of verify_status, it can contain: + + For verify_status == PDKIM_VERIFY_INVALID: + + PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE + Unable to retrieve a public key container. + + PDKIM_VERIFY_INVALID_BUFFER_SIZE + Either the DNS name constructed to retrieve the public key record + does not fit into PDKIM_DNS_TXT_MAX_NAMELEN bytes, or the retrieved + record is longer than PDKIM_DNS_TXT_MAX_RECLEN bytes. + + PDKIM_VERIFY_INVALID_PUBKEY_PARSING + (Syntax) error while parsing the retrieved public key record. + + + For verify_status == PDKIM_VERIFY_FAIL: + + PDKIM_VERIFY_FAIL_BODY + The calculated body hash does not match the advertised body hash + from the bh= tag of the signature. + + PDKIM_VERIFY_FAIL_MESSAGE + RSA verification of the signature (b= tag) failed. + */ + int verify_ext_status; + + /* Pointer to a public key record that was used to verify the signature. + See pdkim_pubkey declaration above for more information. + Caution: is NULL if signing or if no record was retrieved. */ + pdkim_pubkey *pubkey; + + /* Properties below this point are used internally only ------------- */ + + /* Per-signature helper variables ----------------------------------- */ + pdkim_bodyhash *calc_body_hash; /* hash to be / being calculated */ + + pdkim_stringlist *headers; /* Raw headers included in the sig */ + + /* Signing specific ------------------------------------------------- */ + uschar * privkey; /* Private key */ + uschar * sign_headers; /* To-be-signed header names */ + uschar * rawsig_no_b_val; /* Original signature header w/o b= tag value. */ +} pdkim_signature; + + +/* -------------------------------------------------------------------------- */ +/* Context to keep state between all operations. */ +typedef struct pdkim_ctx { + +#define PDKIM_MODE_SIGN BIT(0) /* if unset, mode==verify */ +#define PDKIM_DOT_TERM BIT(1) /* dot termination and unstuffing */ +#define PDKIM_SEEN_CR BIT(2) +#define PDKIM_SEEN_LF BIT(3) +#define PDKIM_PAST_HDRS BIT(4) +#define PDKIM_SEEN_EOD BIT(5) + unsigned flags; + + /* One (signing) or several chained (verification) signatures */ + pdkim_signature *sig; + + /* One (signing) or several chained (verification) bodyhashes */ + pdkim_bodyhash *bodyhash; + + /* Callback for dns/txt query method (verification only) */ + uschar * (*dns_txt_callback)(const uschar *); + + /* Coder's little helpers */ + gstring *cur_header; + uschar *linebuf; + int linebuf_offset; + int num_headers; + pdkim_stringlist *headers; /* Raw headers for verification */ +} pdkim_ctx; + + +/******************************************************************************/ + +typedef struct { + const uschar * dkim_hashname; + hashmethod exim_hashmethod; +} pdkim_hashtype; +extern const pdkim_hashtype pdkim_hashes[]; + +/******************************************************************************/ + + +/* -------------------------------------------------------------------------- */ +/* API functions. Please see the sample code in sample/test_sign.c and + sample/test_verify.c for documentation. +*/ + +#ifdef __cplusplus +extern "C" { +#endif + +void pdkim_init (void); + +void pdkim_init_context (pdkim_ctx *, BOOL, uschar * (*)(const uschar *)); + +DLLEXPORT +pdkim_signature *pdkim_init_sign (pdkim_ctx *, + uschar *, uschar *, uschar *, uschar *, + const uschar **); + +DLLEXPORT +pdkim_ctx *pdkim_init_verify (uschar * (*)(const uschar *), BOOL); + +DLLEXPORT +void pdkim_set_optional (pdkim_signature *, char *, char *,int, int, + long, + unsigned long, + unsigned long); + +int pdkim_hashname_to_hashtype(const uschar *, unsigned); +void pdkim_cstring_to_canons(const uschar *, unsigned, int *, int *); +pdkim_bodyhash *pdkim_set_bodyhash(pdkim_ctx *, int, int, long); +pdkim_bodyhash *pdkim_set_sig_bodyhash(pdkim_ctx *, pdkim_signature *); + +DLLEXPORT +int pdkim_feed (pdkim_ctx *, uschar *, int); +DLLEXPORT +int pdkim_feed_finish (pdkim_ctx *, pdkim_signature **, const uschar **); + +DLLEXPORT +void pdkim_free_ctx (pdkim_ctx *); + + +const uschar * pdkim_errstr(int); + +extern uschar * pdkim_encode_base64(blob *); +extern void pdkim_decode_base64(const uschar *, blob *); +extern void pdkim_hexprint(const uschar *, int); +extern void pdkim_quoteprint(const uschar *, int); +extern pdkim_pubkey * pdkim_parse_pubkey_record(const uschar *); +extern uschar * pdkim_relax_header_n(const uschar *, int, BOOL); +extern uschar * pdkim_relax_header(const uschar *, BOOL); +extern uschar * dkim_sig_to_a_tag(const pdkim_signature *); + +#ifdef __cplusplus +} +#endif + +#endif diff --git a/src/pdkim/pdkim_hash.h b/src/pdkim/pdkim_hash.h new file mode 100644 index 0000000..8f9a126 --- /dev/null +++ b/src/pdkim/pdkim_hash.h @@ -0,0 +1,38 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * + * Copyright (C) 1995 - 2018 Exim maintainers + * + * Hash interface functions + */ + +#include "../exim.h" + +#if !defined(HASH_H) /* entire file */ +#define HASH_H + +#ifdef DISABLE_TLS +# error Must not DISABLE_TLS, for DKIM +#endif + +#include "crypt_ver.h" +#include "../blob.h" +#include "../hash.h" + +#ifdef SIGN_OPENSSL +# include <openssl/rsa.h> +# include <openssl/ssl.h> +# include <openssl/err.h> +#elif defined(SIGN_GNUTLS) +# include <gnutls/gnutls.h> +# include <gnutls/x509.h> +#endif + +#if defined(SHA_OPENSSL) +# include "pdkim.h" +#elif defined(SHA_GCRYPT) +# include "pdkim.h" +#endif + +#endif +/* End of File */ diff --git a/src/pdkim/signing.c b/src/pdkim/signing.c new file mode 100644 index 0000000..d78f31a --- /dev/null +++ b/src/pdkim/signing.c @@ -0,0 +1,903 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * Copyright (c) The Exim Maintainers 1995 - 2022 + * + * signing/verification interface + */ + +#include "../exim.h" +#include "crypt_ver.h" +#include "signing.h" + + +#ifdef MACRO_PREDEF +# include "../macro_predef.h" + +void +features_crypto(void) +{ +# ifdef SIGN_HAVE_ED25519 + builtin_macro_create(US"_CRYPTO_SIGN_ED25519"); +# endif +# ifdef EXIM_HAVE_SHA3 + builtin_macro_create(US"_CRYPTO_HASH_SHA3"); +# endif +} +#else + +#ifndef DISABLE_DKIM /* rest of file */ + +#ifdef DISABLE_TLS +# error Must no DISABLE_TLS, for DKIM +#endif + + +/******************************************************************************/ +#ifdef SIGN_GNUTLS +# define EXIM_GNUTLS_LIBRARY_LOG_LEVEL 3 + +# ifndef GNUTLS_VERIFY_ALLOW_BROKEN +# define GNUTLS_VERIFY_ALLOW_BROKEN 0 +# endif + + +/* Logging function which can be registered with + * gnutls_global_set_log_function() + * gnutls_global_set_log_level() 0..9 + */ +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +static void +exim_gnutls_logger_cb(int level, const char *message) +{ +size_t len = strlen(message); +if (len < 1) + { + DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); + return; + } +DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, + message[len-1] == '\n' ? "" : "\n"); +} +#endif + + + +void +exim_dkim_init(void) +{ +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +DEBUG(D_tls) + { + gnutls_global_set_log_function(exim_gnutls_logger_cb); + /* arbitrarily chosen level; bump upto 9 for more */ + gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); + } +#endif +} + + +/* accumulate data (gnutls-only). String to be appended must be nul-terminated. */ +gstring * +exim_dkim_data_append(gstring * g, uschar * s) +{ +return string_cat(g, s); +} + + + +/* import private key from PEM string in memory. +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) +{ +gnutls_datum_t k = { .data = (void *)privkey_pem, .size = Ustrlen(privkey_pem) }; +gnutls_x509_privkey_t x509_key; +const uschar * where; +int rc; + +if ( (where = US"internal init", rc = gnutls_x509_privkey_init(&x509_key)) + || (rc = gnutls_privkey_init(&sign_ctx->key)) + || (where = US"privkey PEM-block import", + rc = gnutls_x509_privkey_import(x509_key, &k, GNUTLS_X509_FMT_PEM)) + || (where = US"internal privkey transfer", + rc = gnutls_privkey_import_x509(sign_ctx->key, x509_key, 0)) + ) + return string_sprintf("%s: %s", where, gnutls_strerror(rc)); + +switch (rc = gnutls_privkey_get_pk_algorithm(sign_ctx->key, NULL)) + { + case GNUTLS_PK_RSA: sign_ctx->keytype = KEYTYPE_RSA; break; +#ifdef SIGN_HAVE_ED25519 + case GNUTLS_PK_EDDSA_ED25519: sign_ctx->keytype = KEYTYPE_ED25519; break; +#endif + default: return rc < 0 + ? CUS gnutls_strerror(rc) + : string_sprintf("Unhandled key type: %d '%s'", rc, gnutls_pk_get_name(rc)); + } + +return NULL; +} + + + +/* allocate mem for signature (when signing) */ +/* hash & sign data. No way to do incremental. + +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) +{ +gnutls_datum_t k_data = { .data = data->data, .size = data->len }; +gnutls_digest_algorithm_t dig; +gnutls_datum_t k_sig; +int rc; + +switch (hash) + { + case HASH_SHA1: dig = GNUTLS_DIG_SHA1; break; + case HASH_SHA2_256: dig = GNUTLS_DIG_SHA256; break; + case HASH_SHA2_512: dig = GNUTLS_DIG_SHA512; break; + default: return US"nonhandled hash type"; + } + +if ((rc = gnutls_privkey_sign_data(sign_ctx->key, dig, 0, &k_data, &k_sig))) + return CUS gnutls_strerror(rc); + +/* Don't care about deinit for the key; shortlived process */ + +sig->data = k_sig.data; +sig->len = k_sig.size; +return NULL; +} + + + +/* import public key (from blob in memory) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx, + unsigned * bits) +{ +gnutls_datum_t k; +int rc; +const uschar * ret = NULL; + +gnutls_pubkey_init(&verify_ctx->key); +k.data = pubkey->data; +k.size = pubkey->len; + +switch(fmt) + { + case KEYFMT_DER: + if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER))) + ret = US gnutls_strerror(rc); + break; +#ifdef SIGN_HAVE_ED25519 + case KEYFMT_ED25519_BARE: + if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key, + GNUTLS_ECC_CURVE_ED25519, &k, NULL))) + ret = US gnutls_strerror(rc); + break; +#endif + default: + ret = US"pubkey format not handled"; + break; + } +if (!ret && bits) gnutls_pubkey_get_pk_algorithm(verify_ctx->key, bits); +return ret; +} + + +/* verify signature (of hash if RSA sig, of data if EC sig. No way to do incremental) +(given pubkey & alleged sig) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) +{ +gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len }; +gnutls_datum_t s = { .data = sig->data, .size = sig->len }; +int rc; +const uschar * ret = NULL; + +#ifdef SIGN_HAVE_ED25519 +if (verify_ctx->keytype == KEYTYPE_ED25519) + { + if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key, + GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0) + ret = US gnutls_strerror(rc); + } +else +#endif + { + gnutls_sign_algorithm_t algo; + switch (hash) + { + case HASH_SHA1: algo = GNUTLS_SIGN_RSA_SHA1; break; + case HASH_SHA2_256: algo = GNUTLS_SIGN_RSA_SHA256; break; + case HASH_SHA2_512: algo = GNUTLS_SIGN_RSA_SHA512; break; + default: return US"nonhandled hash type"; + } + + if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo, + GNUTLS_VERIFY_ALLOW_BROKEN, &k, &s)) < 0) + ret = US gnutls_strerror(rc); + } + +gnutls_pubkey_deinit(verify_ctx->key); +return ret; +} + + + + +#elif defined(SIGN_GCRYPT) +/******************************************************************************/ +/* This variant is used under pre-3.0.0 GnuTLS. Only rsa-sha1 and rsa-sha256 */ + + +/* Internal service routine: +Read and move past an asn.1 header, checking class & tag, +optionally returning the data-length */ + +static int +as_tag(blob * der, uschar req_cls, long req_tag, long * alen) +{ +int rc; +uschar tag_class; +int taglen; +long tag, len; + +debug_printf_indent("as_tag: %02x %02x %02x %02x\n", + der->data[0], der->data[1], der->data[2], der->data[3]); + +if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag)) + != ASN1_SUCCESS) + return rc; + +if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND; + +if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0) + return ASN1_DER_ERROR; +if (alen) *alen = len; + +/* debug_printf_indent("as_tag: tlen %d dlen %d\n", taglen, (int)len); */ + +der->data += taglen; +der->len -= taglen; +return rc; +} + +/* Internal service routine: +Read and move over an asn.1 integer, setting an MPI to the value +*/ + +static uschar * +as_mpi(blob * der, gcry_mpi_t * mpi) +{ +long alen; +int rc; +gcry_error_t gerr; + +debug_printf_indent("%s\n", __FUNCTION__); + +/* integer; move past the header */ +if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) + return US asn1_strerror(rc); + +/* read to an MPI */ +if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL))) + return US gcry_strerror(gerr); + +/* move over the data */ +der->data += alen; der->len -= alen; +return NULL; +} + + + +void +exim_dkim_init(void) +{ +/* Version check should be the very first call because it +makes sure that important subsystems are initialized. */ +if (!gcry_check_version (GCRYPT_VERSION)) + { + fputs ("libgcrypt version mismatch\n", stderr); + exit (2); + } + +/* We don't want to see any warnings, e.g. because we have not yet +parsed program options which might be used to suppress such +warnings. */ +gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN); + +/* ... If required, other initialization goes here. Note that the +process might still be running with increased privileges and that +the secure memory has not been initialized. */ + +/* Allocate a pool of 16k secure memory. This make the secure memory +available and also drops privileges where needed. */ +gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0); + +/* It is now okay to let Libgcrypt complain when there was/is +a problem with the secure memory. */ +gcry_control (GCRYCTL_RESUME_SECMEM_WARN); + +/* ... If required, other initialization goes here. */ + +/* Tell Libgcrypt that initialization has completed. */ +gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0); + +return; +} + + + + +/* Accumulate data (gnutls-only). +String to be appended must be nul-terminated. */ + +gstring * +exim_dkim_data_append(gstring * g, uschar * s) +{ +return g; /*dummy*/ +} + + + +/* import private key from PEM string in memory. +Only handles RSA keys. +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) +{ +uschar * s1, * s2; +blob der; +long alen; +int rc; + +/*XXX will need extension to _spot_ as well as handle a +non-RSA key? I think... +So... this is not a PrivateKeyInfo - which would have a field +identifying the keytype - PrivateKeyAlgorithmIdentifier - +but a plain RSAPrivateKey (wrapped in PEM-headers. Can we +use those as a type tag? What forms are there? "BEGIN EC PRIVATE KEY" (cf. ec(1ssl)) + +How does OpenSSL PEM_read_bio_PrivateKey() deal with it? +gnutls_x509_privkey_import() ? +*/ + +/* + * RSAPrivateKey ::= SEQUENCE + * version Version, + * modulus INTEGER, -- n + * publicExponent INTEGER, -- e + * privateExponent INTEGER, -- d + * prime1 INTEGER, -- p + * prime2 INTEGER, -- q + * exponent1 INTEGER, -- d mod (p-1) + * exponent2 INTEGER, -- d mod (q-1) + * coefficient INTEGER, -- (inverse of q) mod p + * otherPrimeInfos OtherPrimeInfos OPTIONAL + + * ECPrivateKey ::= SEQUENCE { + * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1), + * privateKey OCTET STRING, + * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL, + * publicKey [1] BIT STRING OPTIONAL + * } + * Hmm, only 1 useful item, and not even an integer? Wonder how we might use it... + +- actually, gnutls_x509_privkey_import() appears to require a curve name parameter + value for that is an OID? a local-only integer (it's an enum in GnuTLS)? + + +Useful cmds: + ssh-keygen -t ecdsa -f foo.privkey + ssh-keygen -t ecdsa -b384 -f foo.privkey + ssh-keygen -t ecdsa -b521 -f foo.privkey + ssh-keygen -t ed25519 -f foo.privkey + + < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x + + openssl asn1parse -in foo -inform PEM -dump + openssl asn1parse -in foo -inform PEM -dump -stroffset 24 (??) +(not good for ed25519) + + */ + +if ( !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----")) + || !(s2 = Ustrstr(CS (s1+=31), "-----END RSA PRIVATE KEY-----" )) + ) + return US"Bad PEM wrapper"; + +*s2 = '\0'; + +if ((rc = b64decode(s1, &der.data) < 0)) + return US"Bad PEM-DER b64 decode"; +der.len = rc; + +/* untangle asn.1 */ + +/* sequence; just move past the header */ +if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) + != ASN1_SUCCESS) goto asn_err; + +/* integer version; move past the header, check is zero */ +if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) + goto asn_err; +if (alen != 1 || *der.data != 0) + return US"Bad version number"; +der.data++; der.len--; + +if ( (s1 = as_mpi(&der, &sign_ctx->n)) + || (s1 = as_mpi(&der, &sign_ctx->e)) + || (s1 = as_mpi(&der, &sign_ctx->d)) + || (s1 = as_mpi(&der, &sign_ctx->p)) + || (s1 = as_mpi(&der, &sign_ctx->q)) + || (s1 = as_mpi(&der, &sign_ctx->dp)) + || (s1 = as_mpi(&der, &sign_ctx->dq)) + || (s1 = as_mpi(&der, &sign_ctx->qp)) + ) + return s1; + +#ifdef extreme_debug +DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n"); + { + uschar * s; + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n); + debug_printf_indent(" N : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e); + debug_printf_indent(" E : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d); + debug_printf_indent(" D : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p); + debug_printf_indent(" P : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q); + debug_printf_indent(" Q : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp); + debug_printf_indent(" DP: %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq); + debug_printf_indent(" DQ: %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp); + debug_printf_indent(" QP: %s\n", s); + } +#endif + +sign_ctx->keytype = KEYTYPE_RSA; +return NULL; + +asn_err: return US asn1_strerror(rc); +} + + + +/* allocate mem for signature (when signing) */ +/* sign already-hashed data. + +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) +{ +char * sexp_hash; +gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL; +gcry_mpi_t m_sig; +uschar * errstr; +gcry_error_t gerr; + +/*XXX will need extension for hash types (though, possibly, should +be re-specced to not rehash but take an already-hashed value? Actually +current impl looks WRONG - it _is_ given a hash so should not be +re-hashing. Has this been tested? + +Will need extension for non-RSA sugning algos. */ + +switch (hash) + { + case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; + case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; + default: return US"nonhandled hash type"; + } + +#define SIGSPACE 128 +sig->data = store_get(SIGSPACE, GET_UNTAINTED); + +if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0) + { + gcry_mpi_swap (sign_ctx->p, sign_ctx->q); + gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q); + } + +if ( (gerr = gcry_sexp_build (&s_key, NULL, + "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))", + sign_ctx->n, sign_ctx->e, + sign_ctx->d, sign_ctx->p, + sign_ctx->q, sign_ctx->qp)) + || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, + (int) data->len, CS data->data)) + || (gerr = gcry_pk_sign (&s_sig, s_hash, s_key)) + ) + return US gcry_strerror(gerr); + +/* gcry_sexp_dump(s_sig); */ + +if ( !(s_sig = gcry_sexp_find_token(s_sig, "s", 0)) + ) + return US"no sig result"; + +m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG); + +#ifdef extreme_debug +DEBUG(D_acl) + { + uschar * s; + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig); + debug_printf_indent(" SG: %s\n", s); + } +#endif + +gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig); +if (gerr) + { + debug_printf_indent("signature conversion from MPI to buffer failed\n"); + return US gcry_strerror(gerr); + } +#undef SIGSPACE + +return NULL; +} + + +/* import public key (from blob in memory) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx, + unsigned * bits) +{ +/* +in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi() +*/ +uschar tag_class; +int taglen; +long alen; +unsigned nbits; +int rc; +uschar * errstr; +gcry_error_t gerr; +uschar * stage = US"S1"; + +if (fmt != KEYFMT_DER) return US"pubkey format not handled"; + +/* +sequence + sequence + OBJECT:rsaEncryption + NULL + BIT STRING:RSAPublicKey + sequence + INTEGER:Public modulus + INTEGER:Public exponent + +openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head; +openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump; +openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22; +*/ + +/* sequence; just move past the header */ +if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) + != ASN1_SUCCESS) goto asn_err; + +/* sequence; skip the entire thing */ +DEBUG(D_acl) stage = US"S2"; +if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen)) + != ASN1_SUCCESS) goto asn_err; +pubkey->data += alen; pubkey->len -= alen; + + +/* bitstring: limit range to size of bitstring; +move over header + content wrapper */ +DEBUG(D_acl) stage = US"BS"; +if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS) + goto asn_err; +pubkey->len = alen; +pubkey->data++; pubkey->len--; + +/* sequence; just move past the header */ +DEBUG(D_acl) stage = US"S3"; +if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) + != ASN1_SUCCESS) goto asn_err; + +/* read two integers */ +DEBUG(D_acl) stage = US"MPI"; +nbits = pubkey->len; +if ((errstr = as_mpi(pubkey, &verify_ctx->n))) return errstr; +nbits = (nbits - pubkey->len) * 8; +if ((errstr = as_mpi(pubkey, &verify_ctx->e))) return errstr; + +#ifdef extreme_debug +DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n"); + { + uschar * s; + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n); + debug_printf_indent(" N : %s\n", s); + gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e); + debug_printf_indent(" E : %s\n", s); + } + +#endif +if (bits) *bits = nbits; +return NULL; + +asn_err: +DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc)); + return US asn1_strerror(rc); +} + + +/* verify signature (of hash) +XXX though we appear to be doing a hash, too! +(given pubkey & alleged sig) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) +{ +/* +cf. libgnutls 2.8.5 _wrap_gcry_pk_verify() +*/ +char * sexp_hash; +gcry_mpi_t m_sig; +gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL; +gcry_error_t gerr; +uschar * stage; + +/*XXX needs extension for SHA512 */ +switch (hash) + { + case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; + case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; + default: return US"nonhandled hash type"; + } + +if ( (stage = US"pkey sexp build", + gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))", + verify_ctx->n, verify_ctx->e)) + || (stage = US"data sexp build", + gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, + (int) data_hash->len, CS data_hash->data)) + || (stage = US"sig mpi scan", + gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL)) + || (stage = US"sig sexp build", + gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig)) + || (stage = US"verify", + gerr = gcry_pk_verify (s_sig, s_hash, s_pkey)) + ) + { + DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage); + return US gcry_strerror(gerr); + } + +if (s_sig) gcry_sexp_release (s_sig); +if (s_hash) gcry_sexp_release (s_hash); +if (s_pkey) gcry_sexp_release (s_pkey); +gcry_mpi_release (m_sig); +gcry_mpi_release (verify_ctx->n); +gcry_mpi_release (verify_ctx->e); + +return NULL; +} + + + + +#elif defined(SIGN_OPENSSL) +/******************************************************************************/ + +void +exim_dkim_init(void) +{ +ERR_load_crypto_strings(); +} + + +/* accumulate data (was gnutls-only but now needed for OpenSSL non-EC too +because now using hash-and-sign interface) */ +gstring * +exim_dkim_data_append(gstring * g, uschar * s) +{ +return string_cat(g, s); +} + + +/* import private key from PEM string in memory. +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) +{ +BIO * bp = BIO_new_mem_buf((void *)privkey_pem, -1); + +if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL))) + return string_sprintf("privkey PEM-block import: %s", + ERR_error_string(ERR_get_error(), NULL)); + +sign_ctx->keytype = +#ifdef SIGN_HAVE_ED25519 + EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_ED25519 + ? KEYTYPE_ED25519 : KEYTYPE_RSA; +#else + KEYTYPE_RSA; +#endif +return NULL; +} + + + +/* allocate mem for signature (when signing) */ +/* hash & sign data. Incremental not supported. + +Return: NULL for success with the signaature in the sig blob, or an error string */ + +const uschar * +exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) +{ +const EVP_MD * md; +EVP_MD_CTX * ctx; +size_t siglen; + +switch (hash) + { + case HASH_NULL: md = NULL; break; /* Ed25519 signing */ + case HASH_SHA1: md = EVP_sha1(); break; + case HASH_SHA2_256: md = EVP_sha256(); break; + case HASH_SHA2_512: md = EVP_sha512(); break; + default: return US"nonhandled hash type"; + } + +#ifdef SIGN_HAVE_ED25519 +if ( (ctx = EVP_MD_CTX_new()) + && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 + && EVP_DigestSign(ctx, NULL, &siglen, NULL, 0) > 0 + && (sig->data = store_get(siglen, GET_UNTAINTED)) + + /* Obtain the signature (slen could change here!) */ + && EVP_DigestSign(ctx, sig->data, &siglen, data->data, data->len) > 0 + ) + { + EVP_MD_CTX_destroy(ctx); + sig->len = siglen; + return NULL; + } +#else +/*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */ +if ( (ctx = EVP_MD_CTX_create()) + && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 + && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0 + && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0 + && (sig->data = store_get(siglen, GET_UNTAINTED)) + + /* Obtain the signature (slen could change here!) */ + && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0 + ) + { + EVP_MD_CTX_destroy(ctx); + sig->len = siglen; + return NULL; + } +#endif + +if (ctx) EVP_MD_CTX_destroy(ctx); +return US ERR_error_string(ERR_get_error(), NULL); +} + + + +/* import public key (from blob in memory) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx, + unsigned * bits) +{ +const uschar * s = pubkey->data; +uschar * ret = NULL; + +switch(fmt) + { + case KEYFMT_DER: + /*XXX hmm, we never free this */ + if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len))) + ret = US ERR_error_string(ERR_get_error(), NULL); + break; +#ifdef SIGN_HAVE_ED25519 + case KEYFMT_ED25519_BARE: + if (!(verify_ctx->key = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL, + s, pubkey->len))) + ret = US ERR_error_string(ERR_get_error(), NULL); + break; +#endif + default: + ret = US"pubkey format not handled"; + break; + } + +if (!ret && bits) *bits = EVP_PKEY_bits(verify_ctx->key); +return ret; +} + + + + +/* verify signature (of hash, except Ed25519 where of-data) +(given pubkey & alleged sig) +Return: NULL for success, or an error string */ + +const uschar * +exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig) +{ +const EVP_MD * md; + +switch (hash) + { + case HASH_NULL: md = NULL; break; + case HASH_SHA1: md = EVP_sha1(); break; + case HASH_SHA2_256: md = EVP_sha256(); break; + case HASH_SHA2_512: md = EVP_sha512(); break; + default: return US"nonhandled hash type"; + } + +#ifdef SIGN_HAVE_ED25519 +if (!md) + { + EVP_MD_CTX * ctx; + + if ((ctx = EVP_MD_CTX_new())) + { + if ( EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0 + && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0 + ) + { EVP_MD_CTX_free(ctx); return NULL; } + EVP_MD_CTX_free(ctx); + } + } +else +#endif + { + EVP_PKEY_CTX * ctx; + + if ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL))) + { + if ( EVP_PKEY_verify_init(ctx) > 0 + && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0 + && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0 + && EVP_PKEY_verify(ctx, sig->data, sig->len, + data->data, data->len) == 1 + ) + { EVP_PKEY_CTX_free(ctx); return NULL; } + EVP_PKEY_CTX_free(ctx); + + DEBUG(D_tls) + if (Ustrcmp(ERR_reason_error_string(ERR_peek_error()), "wrong signature length") == 0) + debug_printf("sig len (from msg hdr): %d, expected (from dns pubkey) %d\n", + (int) sig->len, EVP_PKEY_size(verify_ctx->key)); + } + } + +return US ERR_error_string(ERR_get_error(), NULL); +} + + + +#endif +/******************************************************************************/ + +#endif /*DISABLE_DKIM*/ +#endif /*MACRO_PREDEF*/ +/* End of File */ diff --git a/src/pdkim/signing.h b/src/pdkim/signing.h new file mode 100644 index 0000000..ed6f397 --- /dev/null +++ b/src/pdkim/signing.h @@ -0,0 +1,97 @@ +/* + * PDKIM - a RFC4871 (DKIM) implementation + * + * Copyright (C) 1995 - 2020 Exim maintainers + * + * RSA signing/verification interface + */ + +#include "../exim.h" + +#ifndef DISABLE_DKIM /* entire file */ + +#include "crypt_ver.h" + +#ifdef SIGN_OPENSSL +# include <openssl/rsa.h> +# include <openssl/ssl.h> +# include <openssl/err.h> +#elif defined(SIGN_GNUTLS) +# include <gnutls/gnutls.h> +# include <gnutls/x509.h> +# include <gnutls/abstract.h> +#elif defined(SIGN_GCRYPT) +# include <gcrypt.h> +# include <libtasn1.h> +#endif + +#include "../blob.h" + +typedef enum { + KEYTYPE_RSA, + KEYTYPE_ED25519 +} keytype; + +typedef enum { + KEYFMT_DER, /* an asn.1 structure */ + KEYFMT_ED25519_BARE /* just the key */ +} keyformat; + + +#ifdef SIGN_OPENSSL + +typedef struct { + keytype keytype; + EVP_PKEY * key; +} es_ctx; + +typedef struct { + keytype keytype; + EVP_PKEY * key; +} ev_ctx; + +#elif defined(SIGN_GNUTLS) + +typedef struct { + keytype keytype; + gnutls_privkey_t key; +} es_ctx; + +typedef struct { + keytype keytype; + gnutls_pubkey_t key; +} ev_ctx; + +#elif defined(SIGN_GCRYPT) + +typedef struct { + keytype keytype; + gcry_mpi_t n; + gcry_mpi_t e; + gcry_mpi_t d; + gcry_mpi_t p; + gcry_mpi_t q; + gcry_mpi_t dp; + gcry_mpi_t dq; + gcry_mpi_t qp; +} es_ctx; + +typedef struct { + keytype keytype; + gcry_mpi_t n; + gcry_mpi_t e; +} ev_ctx; + +#endif + + +extern void exim_dkim_init(void); +extern gstring * exim_dkim_data_append(gstring *, uschar *); + +extern const uschar * exim_dkim_signing_init(const uschar *, es_ctx *); +extern const uschar * exim_dkim_sign(es_ctx *, hashmethod, blob *, blob *); +extern const uschar * exim_dkim_verify_init(blob *, keyformat, ev_ctx *, unsigned *); +extern const uschar * exim_dkim_verify(ev_ctx *, hashmethod, blob *, blob *); + +#endif /*DISABLE_DKIM*/ +/* End of File */ |