diff options
Diffstat (limited to 'src/dkim.c')
| -rw-r--r-- | src/dkim.c | 895 |
1 files changed, 895 insertions, 0 deletions
diff --git a/src/dkim.c b/src/dkim.c new file mode 100644 index 0000000..bb916d2 --- /dev/null +++ b/src/dkim.c @@ -0,0 +1,895 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) The Exim Maintainers 2020 - 2022 */ +/* Copyright (c) University of Cambridge, 1995 - 2018 */ +/* See the file NOTICE for conditions of use and distribution. */ + +/* Code for DKIM support. Other DKIM relevant code is in + receive.c, transport.c and transports/smtp.c */ + +#include "exim.h" + +#ifndef DISABLE_DKIM + +# include "pdkim/pdkim.h" + +# ifdef MACRO_PREDEF +# include "macro_predef.h" + +void +params_dkim(void) +{ +builtin_macro_create_var(US"_DKIM_SIGN_HEADERS", US PDKIM_DEFAULT_SIGN_HEADERS); +builtin_macro_create_var(US"_DKIM_OVERSIGN_HEADERS", US PDKIM_OVERSIGN_HEADERS); +} +# else /*!MACRO_PREDEF*/ + + + +pdkim_ctx dkim_sign_ctx; + +int dkim_verify_oldpool; +pdkim_ctx *dkim_verify_ctx = NULL; +pdkim_signature *dkim_cur_sig = NULL; +static const uschar * dkim_collect_error = NULL; + +#define DKIM_MAX_SIGNATURES 20 + + + +/* Look up the DKIM record in DNS for the given hostname. +Will use the first found if there are multiple. +The return string is tainted, having come from off-site. +*/ + +uschar * +dkim_exim_query_dns_txt(const uschar * name) +{ +dns_answer * dnsa = store_get_dns_answer(); +dns_scan dnss; +rmark reset_point = store_mark(); +gstring * g = string_get_tainted(256, GET_TAINTED); + +lookup_dnssec_authenticated = NULL; +if (dns_lookup(dnsa, name, T_TXT, NULL) != DNS_SUCCEED) + goto bad; + +/* Search for TXT record */ + +for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); + rr; + rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) + if (rr->type == T_TXT) + { /* Copy record content to the answer buffer */ + for (int rr_offset = 0; rr_offset < rr->size; ) + { + uschar len = rr->data[rr_offset++]; + + g = string_catn(g, US(rr->data + rr_offset), len); + if (g->ptr >= PDKIM_DNS_TXT_MAX_RECLEN) + goto bad; + + rr_offset += len; + } + + /* Check if this looks like a DKIM record */ + if (Ustrncmp(g->s, "v=", 2) != 0 || strncasecmp(CS g->s, "v=dkim", 6) == 0) + { + store_free_dns_answer(dnsa); + gstring_release_unused(g); + return string_from_gstring(g); + } + + g->ptr = 0; /* overwrite previous record */ + } + +bad: +store_reset(reset_point); +store_free_dns_answer(dnsa); +return NULL; /*XXX better error detail? logging? */ +} + + +void +dkim_exim_init(void) +{ +if (f.dkim_init_done) return; +f.dkim_init_done = TRUE; +pdkim_init(); +} + + + +void +dkim_exim_verify_init(BOOL dot_stuffing) +{ +dkim_exim_init(); + +/* There is a store-reset between header & body reception for the main pool +(actually, after every header line) so cannot use that as we need the data we +store per-header, during header processing, at the end of body reception +for evaluating the signature. Any allocs done for dkim verify +memory-handling must use a different pool. We use a separate one that we +can reset per message. */ + +dkim_verify_oldpool = store_pool; +store_pool = POOL_MESSAGE; + +/* Free previous context if there is one */ + +if (dkim_verify_ctx) + pdkim_free_ctx(dkim_verify_ctx); + +/* Create new context */ + +dkim_verify_ctx = pdkim_init_verify(&dkim_exim_query_dns_txt, dot_stuffing); +dkim_collect_input = dkim_verify_ctx ? DKIM_MAX_SIGNATURES : 0; +dkim_collect_error = NULL; + +/* Start feed up with any cached data, but limited to message data */ +receive_get_cache(chunking_state == CHUNKING_LAST + ? chunking_data_left : GETC_BUFFER_UNLIMITED); + +store_pool = dkim_verify_oldpool; +} + + +/* Submit a chunk of data for verification input. +Only use the data when the feed is activated. */ +void +dkim_exim_verify_feed(uschar * data, int len) +{ +int rc; + +store_pool = POOL_MESSAGE; +if ( dkim_collect_input + && (rc = pdkim_feed(dkim_verify_ctx, data, len)) != PDKIM_OK) + { + dkim_collect_error = pdkim_errstr(rc); + log_write(0, LOG_MAIN, + "DKIM: validation error: %.100s", dkim_collect_error); + dkim_collect_input = 0; + } +store_pool = dkim_verify_oldpool; +} + + +/* Log the result for the given signature */ +static void +dkim_exim_verify_log_sig(pdkim_signature * sig) +{ +gstring * logmsg; +uschar * s; + +if (!sig) return; + +/* Remember the domain for the first pass result */ + +if ( !dkim_verify_overall + && dkim_verify_status + ? Ustrcmp(dkim_verify_status, US"pass") == 0 + : sig->verify_status == PDKIM_VERIFY_PASS + ) + dkim_verify_overall = string_copy(sig->domain); + +/* Rewrite the sig result if the ACL overrode it. This is only +needed because the DMARC code (sigh) peeks at the dkim sigs. +Mark the sig for this having been done. */ + +if ( dkim_verify_status + && ( dkim_verify_status != dkim_exim_expand_query(DKIM_VERIFY_STATUS) + || dkim_verify_reason != dkim_exim_expand_query(DKIM_VERIFY_REASON) + ) ) + { /* overridden by ACL */ + sig->verify_ext_status = -1; + if (Ustrcmp(dkim_verify_status, US"fail") == 0) + sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_FAIL; + else if (Ustrcmp(dkim_verify_status, US"invalid") == 0) + sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_INVALID; + else if (Ustrcmp(dkim_verify_status, US"none") == 0) + sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_NONE; + else if (Ustrcmp(dkim_verify_status, US"pass") == 0) + sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_PASS; + else + sig->verify_status = -1; + } + +if (!LOGGING(dkim_verbose)) return; + + +logmsg = string_catn(NULL, US"DKIM: ", 6); +if (!(s = sig->domain)) s = US"<UNSET>"; +logmsg = string_append(logmsg, 2, "d=", s); +if (!(s = sig->selector)) s = US"<UNSET>"; +logmsg = string_append(logmsg, 2, " s=", s); +logmsg = string_fmt_append(logmsg, " c=%s/%s a=%s b=" SIZE_T_FMT, + sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", + sig->canon_body == PDKIM_CANON_SIMPLE ? "simple" : "relaxed", + dkim_sig_to_a_tag(sig), + (int)sig->sighash.len > -1 ? sig->sighash.len * 8 : (size_t)0); +if ((s= sig->identity)) logmsg = string_append(logmsg, 2, " i=", s); +if (sig->created > 0) logmsg = string_fmt_append(logmsg, " t=%lu", + sig->created); +if (sig->expires > 0) logmsg = string_fmt_append(logmsg, " x=%lu", + sig->expires); +if (sig->bodylength > -1) logmsg = string_fmt_append(logmsg, " l=%lu", + sig->bodylength); + +if (sig->verify_status & PDKIM_VERIFY_POLICY) + logmsg = string_append(logmsg, 5, + US" [", dkim_verify_status, US" - ", dkim_verify_reason, US"]"); +else + switch (sig->verify_status) + { + case PDKIM_VERIFY_NONE: + logmsg = string_cat(logmsg, US" [not verified]"); + break; + + case PDKIM_VERIFY_INVALID: + logmsg = string_cat(logmsg, US" [invalid - "); + switch (sig->verify_ext_status) + { + case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: + logmsg = string_cat(logmsg, + US"public key record (currently?) unavailable]"); + break; + + case PDKIM_VERIFY_INVALID_BUFFER_SIZE: + logmsg = string_cat(logmsg, US"overlong public key record]"); + break; + + case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: + case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: + logmsg = string_cat(logmsg, US"syntax error in public key record]"); + break; + + case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: + logmsg = string_cat(logmsg, US"signature tag missing or invalid]"); + break; + + case PDKIM_VERIFY_INVALID_DKIM_VERSION: + logmsg = string_cat(logmsg, US"unsupported DKIM version]"); + break; + + default: + logmsg = string_cat(logmsg, US"unspecified problem]"); + } + break; + + case PDKIM_VERIFY_FAIL: + logmsg = string_cat(logmsg, US" [verification failed - "); + switch (sig->verify_ext_status) + { + case PDKIM_VERIFY_FAIL_BODY: + logmsg = string_cat(logmsg, + US"body hash mismatch (body probably modified in transit)]"); + break; + + case PDKIM_VERIFY_FAIL_MESSAGE: + logmsg = string_cat(logmsg, + US"signature did not verify " + "(headers probably modified in transit)]"); + break; + + case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: + logmsg = string_cat(logmsg, + US"signature invalid (key too short)]"); + break; + + default: + logmsg = string_cat(logmsg, US"unspecified reason]"); + } + break; + + case PDKIM_VERIFY_PASS: + logmsg = string_cat(logmsg, US" [verification succeeded]"); + break; + } + +log_write(0, LOG_MAIN, "%s", string_from_gstring(logmsg)); +return; +} + + +/* Log a line for each signature */ +void +dkim_exim_verify_log_all(void) +{ +for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) + dkim_exim_verify_log_sig(sig); +} + + +void +dkim_exim_verify_finish(void) +{ +int rc; +gstring * g = NULL; +const uschar * errstr = NULL; + +store_pool = POOL_MESSAGE; + +/* Delete eventual previous signature chain */ + +dkim_signers = NULL; +dkim_signatures = NULL; + +if (dkim_collect_error) + { + log_write(0, LOG_MAIN, + "DKIM: Error during validation, disabling signature verification: %.100s", + dkim_collect_error); + f.dkim_disable_verify = TRUE; + goto out; + } + +dkim_collect_input = 0; + +/* Finish DKIM operation and fetch link to signatures chain */ + +rc = pdkim_feed_finish(dkim_verify_ctx, (pdkim_signature **)&dkim_signatures, + &errstr); +if (rc != PDKIM_OK && errstr) + log_write(0, LOG_MAIN, "DKIM: validation error: %s", errstr); + +/* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */ + +for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) + { + if (sig->domain) g = string_append_listele(g, ':', sig->domain); + if (sig->identity) g = string_append_listele(g, ':', sig->identity); + } + +if (g) dkim_signers = g->s; + +out: +store_pool = dkim_verify_oldpool; +} + + + +/* Args as per dkim_exim_acl_run() below */ +static int +dkim_acl_call(uschar * id, gstring ** res_ptr, + uschar ** user_msgptr, uschar ** log_msgptr) +{ +int rc; +DEBUG(D_receive) + debug_printf("calling acl_smtp_dkim for dkim_cur_signer='%s'\n", id); + +rc = acl_check(ACL_WHERE_DKIM, NULL, acl_smtp_dkim, user_msgptr, log_msgptr); +dkim_exim_verify_log_sig(dkim_cur_sig); +*res_ptr = string_append_listele(*res_ptr, ':', dkim_verify_status); +return rc; +} + + + +/* For the given identity, run the DKIM ACL once for each matching signature. + +Arguments + id Identity to look for in dkim signatures + res_ptr ptr to growable string-list of status results, + appended to per ACL run + user_msgptr where to put a user error (for SMTP response) + log_msgptr where to put a logging message (not for SMTP response) + +Returns: OK access is granted by an ACCEPT verb + DISCARD access is granted by a DISCARD verb + FAIL access is denied + FAIL_DROP access is denied; drop the connection + DEFER can't tell at the moment + ERROR disaster +*/ + +int +dkim_exim_acl_run(uschar * id, gstring ** res_ptr, + uschar ** user_msgptr, uschar ** log_msgptr) +{ +uschar * cmp_val; +int rc = -1; + +dkim_verify_status = US"none"; +dkim_verify_reason = US""; +dkim_cur_signer = id; + +if (f.dkim_disable_verify || !id || !dkim_verify_ctx) + return OK; + +/* Find signatures to run ACL on */ + +for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) + if ( (cmp_val = Ustrchr(id, '@') != NULL ? US sig->identity : US sig->domain) + && strcmpic(cmp_val, id) == 0 + ) + { + /* The "dkim_domain" and "dkim_selector" expansion variables have + related globals, since they are used in the signing code too. + Instead of inventing separate names for verification, we set + them here. This is easy since a domain and selector is guaranteed + to be in a signature. The other dkim_* expansion items are + dynamically fetched from dkim_cur_sig at expansion time (see + dkim_exim_expand_query() below). */ + + dkim_cur_sig = sig; + dkim_signing_domain = US sig->domain; + dkim_signing_selector = US sig->selector; + dkim_key_length = sig->keybits; + + /* These two return static strings, so we can compare the addr + later to see if the ACL overwrote them. Check that when logging */ + + dkim_verify_status = dkim_exim_expand_query(DKIM_VERIFY_STATUS); + dkim_verify_reason = dkim_exim_expand_query(DKIM_VERIFY_REASON); + + if ((rc = dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr)) != OK) + return rc; + } + +if (rc != -1) + return rc; + +/* No matching sig found. Call ACL once anyway. */ + +dkim_cur_sig = NULL; +return dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr); +} + + +static uschar * +dkim_exim_expand_defaults(int what) +{ +switch (what) + { + case DKIM_ALGO: return US""; + case DKIM_BODYLENGTH: return US"9999999999999"; + case DKIM_CANON_BODY: return US""; + case DKIM_CANON_HEADERS: return US""; + case DKIM_COPIEDHEADERS: return US""; + case DKIM_CREATED: return US"0"; + case DKIM_EXPIRES: return US"9999999999999"; + case DKIM_HEADERNAMES: return US""; + case DKIM_IDENTITY: return US""; + case DKIM_KEY_GRANULARITY: return US"*"; + case DKIM_KEY_SRVTYPE: return US"*"; + case DKIM_KEY_NOTES: return US""; + case DKIM_KEY_TESTING: return US"0"; + case DKIM_NOSUBDOMAINS: return US"0"; + case DKIM_VERIFY_STATUS: return US"none"; + case DKIM_VERIFY_REASON: return US""; + default: return US""; + } +} + + +uschar * +dkim_exim_expand_query(int what) +{ +if (!dkim_verify_ctx || f.dkim_disable_verify || !dkim_cur_sig) + return dkim_exim_expand_defaults(what); + +switch (what) + { + case DKIM_ALGO: + return dkim_sig_to_a_tag(dkim_cur_sig); + + case DKIM_BODYLENGTH: + return dkim_cur_sig->bodylength >= 0 + ? string_sprintf("%ld", dkim_cur_sig->bodylength) + : dkim_exim_expand_defaults(what); + + case DKIM_CANON_BODY: + switch (dkim_cur_sig->canon_body) + { + case PDKIM_CANON_RELAXED: return US"relaxed"; + case PDKIM_CANON_SIMPLE: + default: return US"simple"; + } + + case DKIM_CANON_HEADERS: + switch (dkim_cur_sig->canon_headers) + { + case PDKIM_CANON_RELAXED: return US"relaxed"; + case PDKIM_CANON_SIMPLE: + default: return US"simple"; + } + + case DKIM_COPIEDHEADERS: + return dkim_cur_sig->copiedheaders + ? US dkim_cur_sig->copiedheaders : dkim_exim_expand_defaults(what); + + case DKIM_CREATED: + return dkim_cur_sig->created > 0 + ? string_sprintf("%lu", dkim_cur_sig->created) + : dkim_exim_expand_defaults(what); + + case DKIM_EXPIRES: + return dkim_cur_sig->expires > 0 + ? string_sprintf("%lu", dkim_cur_sig->expires) + : dkim_exim_expand_defaults(what); + + case DKIM_HEADERNAMES: + return dkim_cur_sig->headernames + ? dkim_cur_sig->headernames : dkim_exim_expand_defaults(what); + + case DKIM_IDENTITY: + return dkim_cur_sig->identity + ? US dkim_cur_sig->identity : dkim_exim_expand_defaults(what); + + case DKIM_KEY_GRANULARITY: + return dkim_cur_sig->pubkey + ? dkim_cur_sig->pubkey->granularity + ? US dkim_cur_sig->pubkey->granularity + : dkim_exim_expand_defaults(what) + : dkim_exim_expand_defaults(what); + + case DKIM_KEY_SRVTYPE: + return dkim_cur_sig->pubkey + ? dkim_cur_sig->pubkey->srvtype + ? US dkim_cur_sig->pubkey->srvtype + : dkim_exim_expand_defaults(what) + : dkim_exim_expand_defaults(what); + + case DKIM_KEY_NOTES: + return dkim_cur_sig->pubkey + ? dkim_cur_sig->pubkey->notes + ? US dkim_cur_sig->pubkey->notes + : dkim_exim_expand_defaults(what) + : dkim_exim_expand_defaults(what); + + case DKIM_KEY_TESTING: + return dkim_cur_sig->pubkey + ? dkim_cur_sig->pubkey->testing + ? US"1" + : dkim_exim_expand_defaults(what) + : dkim_exim_expand_defaults(what); + + case DKIM_NOSUBDOMAINS: + return dkim_cur_sig->pubkey + ? dkim_cur_sig->pubkey->no_subdomaining + ? US"1" + : dkim_exim_expand_defaults(what) + : dkim_exim_expand_defaults(what); + + case DKIM_VERIFY_STATUS: + switch (dkim_cur_sig->verify_status) + { + case PDKIM_VERIFY_INVALID: return US"invalid"; + case PDKIM_VERIFY_FAIL: return US"fail"; + case PDKIM_VERIFY_PASS: return US"pass"; + case PDKIM_VERIFY_NONE: + default: return US"none"; + } + + case DKIM_VERIFY_REASON: + switch (dkim_cur_sig->verify_ext_status) + { + case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: + return US"pubkey_unavailable"; + case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:return US"pubkey_dns_syntax"; + case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: return US"pubkey_der_syntax"; + case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: return US"pubkey_too_short"; + case PDKIM_VERIFY_FAIL_BODY: return US"bodyhash_mismatch"; + case PDKIM_VERIFY_FAIL_MESSAGE: return US"signature_incorrect"; + } + + default: + return US""; + } +} + + +void +dkim_exim_sign_init(void) +{ +int old_pool = store_pool; + +dkim_exim_init(); +store_pool = POOL_MAIN; +pdkim_init_context(&dkim_sign_ctx, FALSE, &dkim_exim_query_dns_txt); +store_pool = old_pool; +} + + +/* Generate signatures for the given file. +If a prefix is given, prepend it to the file for the calculations. + +Return: + NULL: error; error string written + string: signature header(s), or a zero-length string (not an error) +*/ + +gstring * +dkim_exim_sign(int fd, off_t off, uschar * prefix, + struct ob_dkim * dkim, const uschar ** errstr) +{ +const uschar * dkim_domain = NULL; +int sep = 0; +gstring * seen_doms = NULL; +pdkim_signature * sig; +gstring * sigbuf; +int pdkim_rc; +int sread; +uschar buf[4096]; +int save_errno = 0; +int old_pool = store_pool; +uschar * errwhen; +const uschar * s; + +if (dkim->dot_stuffed) + dkim_sign_ctx.flags |= PDKIM_DOT_TERM; + +store_pool = POOL_MAIN; + +if ((s = dkim->dkim_domain) && !(dkim_domain = expand_cstring(s))) + /* expansion error, do not send message. */ + { errwhen = US"dkim_domain"; goto expand_bad; } + +/* Set $dkim_domain expansion variable to each unique domain in list. */ + +if (dkim_domain) + while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 0))) + { + const uschar * dkim_sel; + int sel_sep = 0; + + if (dkim_signing_domain[0] == '\0') + continue; + + /* Only sign once for each domain, no matter how often it + appears in the expanded list. */ + + dkim_signing_domain = string_copylc(dkim_signing_domain); + if (match_isinlist(dkim_signing_domain, CUSS &seen_doms, + 0, NULL, NULL, MCL_STRING, TRUE, NULL) == OK) + continue; + + seen_doms = string_append_listele(seen_doms, ':', dkim_signing_domain); + + /* Set $dkim_selector expansion variable to each selector in list, + for this domain. */ + + if (!(dkim_sel = expand_string(dkim->dkim_selector))) + { errwhen = US"dkim_selector"; goto expand_bad; } + + while ((dkim_signing_selector = string_nextinlist(&dkim_sel, &sel_sep, + NULL, 0))) + { + uschar * dkim_canon_expanded; + int pdkim_canon; + uschar * dkim_sign_headers_expanded = NULL; + uschar * dkim_private_key_expanded; + uschar * dkim_hash_expanded; + uschar * dkim_identity_expanded = NULL; + uschar * dkim_timestamps_expanded = NULL; + unsigned long tval = 0, xval = 0; + + /* Get canonicalization to use */ + + dkim_canon_expanded = dkim->dkim_canon + ? expand_string(dkim->dkim_canon) : US"relaxed"; + if (!dkim_canon_expanded) /* expansion error, do not send message. */ + { errwhen = US"dkim_canon"; goto expand_bad; } + + if (Ustrcmp(dkim_canon_expanded, "relaxed") == 0) + pdkim_canon = PDKIM_CANON_RELAXED; + else if (Ustrcmp(dkim_canon_expanded, "simple") == 0) + pdkim_canon = PDKIM_CANON_SIMPLE; + else + { + log_write(0, LOG_MAIN, + "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n", + dkim_canon_expanded); + pdkim_canon = PDKIM_CANON_RELAXED; + } + + if ( dkim->dkim_sign_headers + && !(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers))) + { errwhen = US"dkim_sign_header"; goto expand_bad; } + /* else pass NULL, which means default header list */ + + /* Get private key to use. */ + + if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key))) + { errwhen = US"dkim_private_key"; goto expand_bad; } + + if ( Ustrlen(dkim_private_key_expanded) == 0 + || Ustrcmp(dkim_private_key_expanded, "0") == 0 + || Ustrcmp(dkim_private_key_expanded, "false") == 0 + ) + continue; /* don't sign, but no error */ + + if ( dkim_private_key_expanded[0] == '/' + && !(dkim_private_key_expanded = + expand_file_big_buffer(dkim_private_key_expanded))) + goto bad; + + if (!(dkim_hash_expanded = expand_string(dkim->dkim_hash))) + { errwhen = US"dkim_hash"; goto expand_bad; } + + if (dkim->dkim_identity) + if (!(dkim_identity_expanded = expand_string(dkim->dkim_identity))) + { errwhen = US"dkim_identity"; goto expand_bad; } + else if (!*dkim_identity_expanded) + dkim_identity_expanded = NULL; + + if (dkim->dkim_timestamps) + if (!(dkim_timestamps_expanded = expand_string(dkim->dkim_timestamps))) + { errwhen = US"dkim_timestamps"; goto expand_bad; } + else + xval = (tval = (unsigned long) time(NULL)) + + strtoul(CCS dkim_timestamps_expanded, NULL, 10); + + if (!(sig = pdkim_init_sign(&dkim_sign_ctx, dkim_signing_domain, + dkim_signing_selector, + dkim_private_key_expanded, + dkim_hash_expanded, + errstr + ))) + goto bad; + dkim_private_key_expanded[0] = '\0'; + + pdkim_set_optional(sig, + CS dkim_sign_headers_expanded, + CS dkim_identity_expanded, + pdkim_canon, + pdkim_canon, -1, tval, xval); + + if (!pdkim_set_sig_bodyhash(&dkim_sign_ctx, sig)) + goto bad; + + if (!dkim_sign_ctx.sig) /* link sig to context chain */ + dkim_sign_ctx.sig = sig; + else + { + pdkim_signature * n = dkim_sign_ctx.sig; + while (n->next) n = n->next; + n->next = sig; + } + } + } + +/* We may need to carry on with the data-feed even if there are no DKIM sigs to +produce, if some other package (eg. ARC) is signing. */ + +if (!dkim_sign_ctx.sig && !dkim->force_bodyhash) + { + DEBUG(D_transport) debug_printf("DKIM: no viable signatures to use\n"); + sigbuf = string_get(1); /* return a zero-len string */ + } +else + { + if (prefix && (pdkim_rc = pdkim_feed(&dkim_sign_ctx, prefix, Ustrlen(prefix))) != PDKIM_OK) + goto pk_bad; + + if (lseek(fd, off, SEEK_SET) < 0) + sread = -1; + else + while ((sread = read(fd, &buf, sizeof(buf))) > 0) + if ((pdkim_rc = pdkim_feed(&dkim_sign_ctx, buf, sread)) != PDKIM_OK) + goto pk_bad; + + /* Handle failed read above. */ + if (sread == -1) + { + debug_printf("DKIM: Error reading -K file.\n"); + save_errno = errno; + goto bad; + } + + /* Build string of headers, one per signature */ + + if ((pdkim_rc = pdkim_feed_finish(&dkim_sign_ctx, &sig, errstr)) != PDKIM_OK) + goto pk_bad; + + if (!sig) + { + DEBUG(D_transport) debug_printf("DKIM: no signatures to use\n"); + sigbuf = string_get(1); /* return a zero-len string */ + } + else for (sigbuf = NULL; sig; sig = sig->next) + sigbuf = string_append(sigbuf, 2, US sig->signature_header, US"\r\n"); + } + +CLEANUP: + (void) string_from_gstring(sigbuf); + store_pool = old_pool; + errno = save_errno; + return sigbuf; + +pk_bad: + log_write(0, LOG_MAIN|LOG_PANIC, + "DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc)); +bad: + sigbuf = NULL; + goto CLEANUP; + +expand_bad: + *errstr = string_sprintf("failed to expand %s: %s", + errwhen, expand_string_message); + log_write(0, LOG_MAIN | LOG_PANIC, "%s", *errstr); + goto bad; +} + + + + +gstring * +authres_dkim(gstring * g) +{ +int start = 0; /* compiler quietening */ + +DEBUG(D_acl) start = g->ptr; + +for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next) + { + g = string_catn(g, US";\n\tdkim=", 8); + + if (sig->verify_status & PDKIM_VERIFY_POLICY) + g = string_append(g, 5, + US"policy (", dkim_verify_status, US" - ", dkim_verify_reason, US")"); + else switch(sig->verify_status) + { + case PDKIM_VERIFY_NONE: g = string_cat(g, US"none"); break; + case PDKIM_VERIFY_INVALID: + switch (sig->verify_ext_status) + { + case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE: + g = string_cat(g, US"tmperror (pubkey unavailable)\n\t\t"); break; + case PDKIM_VERIFY_INVALID_BUFFER_SIZE: + g = string_cat(g, US"permerror (overlong public key record)\n\t\t"); break; + case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD: + case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT: + g = string_cat(g, US"neutral (public key record import problem)\n\t\t"); + break; + case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR: + g = string_cat(g, US"neutral (signature tag missing or invalid)\n\t\t"); + break; + case PDKIM_VERIFY_INVALID_DKIM_VERSION: + g = string_cat(g, US"neutral (unsupported DKIM version)\n\t\t"); + break; + default: + g = string_cat(g, US"permerror (unspecified problem)\n\t\t"); break; + } + break; + case PDKIM_VERIFY_FAIL: + switch (sig->verify_ext_status) + { + case PDKIM_VERIFY_FAIL_BODY: + g = string_cat(g, + US"fail (body hash mismatch; body probably modified in transit)\n\t\t"); + break; + case PDKIM_VERIFY_FAIL_MESSAGE: + g = string_cat(g, + US"fail (signature did not verify; headers probably modified in transit)\n\t\t"); + break; + case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE: /* should this really be "polcy"? */ + g = string_fmt_append(g, "fail (public key too short: %u bits)\n\t\t", sig->keybits); + break; + default: + g = string_cat(g, US"fail (unspecified reason)\n\t\t"); + break; + } + break; + case PDKIM_VERIFY_PASS: g = string_cat(g, US"pass"); break; + default: g = string_cat(g, US"permerror"); break; + } + if (sig->domain) g = string_append(g, 2, US" header.d=", sig->domain); + if (sig->identity) g = string_append(g, 2, US" header.i=", sig->identity); + if (sig->selector) g = string_append(g, 2, US" header.s=", sig->selector); + g = string_append(g, 2, US" header.a=", dkim_sig_to_a_tag(sig)); + } + +DEBUG(D_acl) + if (g->ptr == start) + debug_printf("DKIM: no authres\n"); + else + debug_printf("DKIM: authres '%.*s'\n", g->ptr - start - 3, g->s + start + 3); +return g; +} + + +# endif /*!MACRO_PREDEF*/ +#endif /*!DISABLE_DKIM*/ |