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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 09:59:15 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 09:59:15 +0000 |
commit | 8de1ee1b2b676b0d07586f0752750dd6b0fb7511 (patch) | |
tree | dd46fd7dc3863045696cd0e48032d8a36fa0daf5 /agent/pksign.c | |
parent | Initial commit. (diff) | |
download | gnupg2-upstream.tar.xz gnupg2-upstream.zip |
Adding upstream version 2.2.27.upstream/2.2.27upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'agent/pksign.c')
-rw-r--r-- | agent/pksign.c | 572 |
1 files changed, 572 insertions, 0 deletions
diff --git a/agent/pksign.c b/agent/pksign.c new file mode 100644 index 0000000..09d61b8 --- /dev/null +++ b/agent/pksign.c @@ -0,0 +1,572 @@ +/* pksign.c - public key signing (well, actually using a secret key) + * Copyright (C) 2001-2004, 2010 Free Software Foundation, Inc. + * Copyright (C) 2001-2004, 2010, 2013 Werner Koch + * + * This file is part of GnuPG. + * + * GnuPG 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 3 of the License, or + * (at your option) any later version. + * + * GnuPG 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, see <https://www.gnu.org/licenses/>. + */ + +#include <config.h> +#include <errno.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <ctype.h> +#include <assert.h> +#include <unistd.h> +#include <sys/stat.h> + +#include "agent.h" +#include "../common/i18n.h" + + +static int +do_encode_md (const byte * md, size_t mdlen, int algo, gcry_sexp_t * r_hash, + int raw_value) +{ + gcry_sexp_t hash; + int rc; + + if (!raw_value) + { + const char *s; + char tmp[16+1]; + int i; + + s = gcry_md_algo_name (algo); + if (s && strlen (s) < 16) + { + for (i=0; i < strlen (s); i++) + tmp[i] = tolower (s[i]); + tmp[i] = '\0'; + } + + rc = gcry_sexp_build (&hash, NULL, + "(data (flags pkcs1) (hash %s %b))", + tmp, (int)mdlen, md); + } + else + { + gcry_mpi_t mpi; + + rc = gcry_mpi_scan (&mpi, GCRYMPI_FMT_USG, md, mdlen, NULL); + if (!rc) + { + rc = gcry_sexp_build (&hash, NULL, + "(data (flags raw) (value %m))", + mpi); + gcry_mpi_release (mpi); + } + else + hash = NULL; + + } + + *r_hash = hash; + return rc; +} + + +/* Return the number of bits of the Q parameter from the DSA key + KEY. */ +static unsigned int +get_dsa_qbits (gcry_sexp_t key) +{ + gcry_sexp_t l1, l2; + gcry_mpi_t q; + unsigned int nbits; + + l1 = gcry_sexp_find_token (key, "private-key", 0); + if (!l1) + l1 = gcry_sexp_find_token (key, "protected-private-key", 0); + if (!l1) + l1 = gcry_sexp_find_token (key, "shadowed-private-key", 0); + if (!l1) + l1 = gcry_sexp_find_token (key, "public-key", 0); + if (!l1) + return 0; /* Does not contain a key object. */ + l2 = gcry_sexp_cadr (l1); + gcry_sexp_release (l1); + l1 = gcry_sexp_find_token (l2, "q", 1); + gcry_sexp_release (l2); + if (!l1) + return 0; /* Invalid object. */ + q = gcry_sexp_nth_mpi (l1, 1, GCRYMPI_FMT_USG); + gcry_sexp_release (l1); + if (!q) + return 0; /* Missing value. */ + nbits = gcry_mpi_get_nbits (q); + gcry_mpi_release (q); + + return nbits; +} + + +/* Return an appropriate hash algorithm to be used with RFC-6979 for a + message digest of length MDLEN. Although a fallback of SHA-256 is + used the current implementation in Libgcrypt will reject a hash + algorithm which does not match the length of the message. */ +static const char * +rfc6979_hash_algo_string (size_t mdlen) +{ + switch (mdlen) + { + case 20: return "sha1"; + case 28: return "sha224"; + case 32: return "sha256"; + case 48: return "sha384"; + case 64: return "sha512"; + default: return "sha256"; + } +} + + +/* Encode a message digest for use with the EdDSA algorithm + (i.e. curve Ed25519). */ +static gpg_error_t +do_encode_eddsa (const byte *md, size_t mdlen, gcry_sexp_t *r_hash) +{ + gpg_error_t err; + gcry_sexp_t hash; + + *r_hash = NULL; + err = gcry_sexp_build (&hash, NULL, + "(data(flags eddsa)(hash-algo sha512)(value %b))", + (int)mdlen, md); + if (!err) + *r_hash = hash; + return err; +} + + +/* Encode a message digest for use with an DSA algorithm. */ +static gpg_error_t +do_encode_dsa (const byte *md, size_t mdlen, int pkalgo, gcry_sexp_t pkey, + gcry_sexp_t *r_hash) +{ + gpg_error_t err; + gcry_sexp_t hash; + unsigned int qbits; + + *r_hash = NULL; + + if (pkalgo == GCRY_PK_ECDSA) + qbits = gcry_pk_get_nbits (pkey); + else if (pkalgo == GCRY_PK_DSA) + qbits = get_dsa_qbits (pkey); + else + return gpg_error (GPG_ERR_WRONG_PUBKEY_ALGO); + + if (pkalgo == GCRY_PK_DSA && (qbits%8)) + { + /* FIXME: We check the QBITS but print a message about the hash + length. */ + log_error (_("DSA requires the hash length to be a" + " multiple of 8 bits\n")); + return gpg_error (GPG_ERR_INV_LENGTH); + } + + /* Don't allow any Q smaller than 160 bits. We don't want someone + to issue signatures from a key with a 16-bit Q or something like + that, which would look correct but allow trivial forgeries. Yes, + I know this rules out using MD5 with DSA. ;) */ + if (qbits < 160) + { + log_error (_("%s key uses an unsafe (%u bit) hash\n"), + gcry_pk_algo_name (pkalgo), qbits); + return gpg_error (GPG_ERR_INV_LENGTH); + } + + /* ECDSA 521 is special has it is larger than the largest hash + we have (SHA-512). Thus we change the size for further + processing to 512. */ + if (pkalgo == GCRY_PK_ECDSA && qbits > 512) + qbits = 512; + + /* Check if we're too short. Too long is safe as we'll + automatically left-truncate. */ + if (mdlen < qbits/8) + { + log_error (_("a %zu bit hash is not valid for a %u bit %s key\n"), + mdlen*8, + gcry_pk_get_nbits (pkey), + gcry_pk_algo_name (pkalgo)); + return gpg_error (GPG_ERR_INV_LENGTH); + } + + /* Truncate. */ + if (mdlen > qbits/8) + mdlen = qbits/8; + + /* Create the S-expression. */ + err = gcry_sexp_build (&hash, NULL, + "(data (flags rfc6979) (hash %s %b))", + rfc6979_hash_algo_string (mdlen), + (int)mdlen, md); + if (!err) + *r_hash = hash; + return err; +} + + +/* Special version of do_encode_md to take care of pkcs#1 padding. + For TLS-MD5SHA1 we need to do the padding ourself as Libgrypt does + not know about this special scheme. Fixme: We should have a + pkcs1-only-padding flag for Libgcrypt. */ +static int +do_encode_raw_pkcs1 (const byte *md, size_t mdlen, unsigned int nbits, + gcry_sexp_t *r_hash) +{ + int rc; + gcry_sexp_t hash; + unsigned char *frame; + size_t i, n, nframe; + + nframe = (nbits+7) / 8; + if ( !mdlen || mdlen + 8 + 4 > nframe ) + { + /* Can't encode this hash into a frame of size NFRAME. */ + return gpg_error (GPG_ERR_TOO_SHORT); + } + + frame = xtrymalloc (nframe); + if (!frame) + return gpg_error_from_syserror (); + + /* Assemble the pkcs#1 block type 1. */ + n = 0; + frame[n++] = 0; + frame[n++] = 1; /* Block type. */ + i = nframe - mdlen - 3 ; + assert (i >= 8); /* At least 8 bytes of padding. */ + memset (frame+n, 0xff, i ); + n += i; + frame[n++] = 0; + memcpy (frame+n, md, mdlen ); + n += mdlen; + assert (n == nframe); + + /* Create the S-expression. */ + rc = gcry_sexp_build (&hash, NULL, + "(data (flags raw) (value %b))", + (int)nframe, frame); + xfree (frame); + + *r_hash = hash; + return rc; +} + + + +/* SIGN whatever information we have accumulated in CTRL and return + * the signature S-expression. LOOKUP is an optional function to + * provide a way for lower layers to ask for the caching TTL. If a + * CACHE_NONCE is given that cache item is first tried to get a + * passphrase. If OVERRIDEDATA is not NULL, OVERRIDEDATALEN bytes + * from this buffer are used instead of the data in CTRL. The + * override feature is required to allow the use of Ed25519 with ssh + * because Ed25519 does the hashing itself. */ +gpg_error_t +agent_pksign_do (ctrl_t ctrl, const char *cache_nonce, + const char *desc_text, + gcry_sexp_t *signature_sexp, + cache_mode_t cache_mode, lookup_ttl_t lookup_ttl, + const void *overridedata, size_t overridedatalen) +{ + gpg_error_t err = 0; + gcry_sexp_t s_skey = NULL; + gcry_sexp_t s_sig = NULL; + gcry_sexp_t s_hash = NULL; + gcry_sexp_t s_pkey = NULL; + unsigned char *shadow_info = NULL; + const unsigned char *data; + int datalen; + int check_signature = 0; + + if (overridedata) + { + data = overridedata; + datalen = overridedatalen; + } + else + { + data = ctrl->digest.value; + datalen = ctrl->digest.valuelen; + } + + if (!ctrl->have_keygrip) + return gpg_error (GPG_ERR_NO_SECKEY); + + err = agent_key_from_file (ctrl, cache_nonce, desc_text, ctrl->keygrip, + &shadow_info, cache_mode, lookup_ttl, + &s_skey, NULL); + if (err) + { + if (gpg_err_code (err) != GPG_ERR_NO_SECKEY) + log_error ("failed to read the secret key\n"); + goto leave; + } + + if (shadow_info) + { + /* Divert operation to the smartcard */ + size_t len; + unsigned char *buf = NULL; + int key_type; + int is_RSA = 0; + int is_ECDSA = 0; + int is_EdDSA = 0; + + err = agent_public_key_from_file (ctrl, ctrl->keygrip, &s_pkey); + if (err) + { + log_error ("failed to read the public key\n"); + goto leave; + } + + if (agent_is_eddsa_key (s_skey)) + is_EdDSA = 1; + else + { + key_type = agent_is_dsa_key (s_skey); + if (key_type == 0) + is_RSA = 1; + else if (key_type == GCRY_PK_ECDSA) + is_ECDSA = 1; + } + + { + char *desc2 = NULL; + + if (desc_text) + agent_modify_description (desc_text, NULL, s_skey, &desc2); + + err = divert_pksign (ctrl, desc2? desc2 : desc_text, + data, datalen, + ctrl->digest.algo, + ctrl->keygrip, + shadow_info, &buf, &len); + xfree (desc2); + } + if (err) + { + log_error ("smartcard signing failed: %s\n", gpg_strerror (err)); + goto leave; + } + + if (is_RSA) + { + check_signature = 1; + if (*buf & 0x80) + { + len++; + buf = xtryrealloc (buf, len); + if (!buf) + goto leave; + + memmove (buf + 1, buf, len - 1); + *buf = 0; + } + + err = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%b)))", + (int)len, buf); + } + else if (is_EdDSA) + { + err = gcry_sexp_build (&s_sig, NULL, "(sig-val(eddsa(r%b)(s%b)))", + (int)len/2, buf, (int)len/2, buf + len/2); + } + else if (is_ECDSA) + { + unsigned char *r_buf_allocated = NULL; + unsigned char *s_buf_allocated = NULL; + unsigned char *r_buf, *s_buf; + int r_buflen, s_buflen; + + r_buflen = s_buflen = len/2; + + if (*buf & 0x80) + { + r_buflen++; + r_buf_allocated = xtrymalloc (r_buflen); + if (!r_buf_allocated) + { + err = gpg_error_from_syserror (); + goto leave; + } + + r_buf = r_buf_allocated; + memcpy (r_buf + 1, buf, len/2); + *r_buf = 0; + } + else + r_buf = buf; + + if (*(buf + len/2) & 0x80) + { + s_buflen++; + s_buf_allocated = xtrymalloc (s_buflen); + if (!s_buf_allocated) + { + err = gpg_error_from_syserror (); + xfree (r_buf_allocated); + goto leave; + } + + s_buf = s_buf_allocated; + memcpy (s_buf + 1, buf + len/2, len/2); + *s_buf = 0; + } + else + s_buf = buf + len/2; + + err = gcry_sexp_build (&s_sig, NULL, "(sig-val(ecdsa(r%b)(s%b)))", + r_buflen, r_buf, + s_buflen, s_buf); + xfree (r_buf_allocated); + xfree (s_buf_allocated); + } + else + err = gpg_error (GPG_ERR_NOT_IMPLEMENTED); + + xfree (buf); + if (err) + { + log_error ("failed to convert sigbuf returned by divert_pksign " + "into S-Exp: %s", gpg_strerror (err)); + goto leave; + } + } + else + { + /* No smartcard, but a private key */ + int dsaalgo = 0; + + /* Put the hash into a sexp */ + if (agent_is_eddsa_key (s_skey)) + err = do_encode_eddsa (data, datalen, + &s_hash); + else if (ctrl->digest.algo == MD_USER_TLS_MD5SHA1) + err = do_encode_raw_pkcs1 (data, datalen, + gcry_pk_get_nbits (s_skey), + &s_hash); + else if ( (dsaalgo = agent_is_dsa_key (s_skey)) ) + err = do_encode_dsa (data, datalen, + dsaalgo, s_skey, + &s_hash); + else + err = do_encode_md (data, datalen, + ctrl->digest.algo, + &s_hash, + ctrl->digest.raw_value); + if (err) + goto leave; + + if (DBG_CRYPTO) + { + gcry_log_debugsxp ("skey", s_skey); + gcry_log_debugsxp ("hash", s_hash); + } + + /* sign */ + err = gcry_pk_sign (&s_sig, s_hash, s_skey); + if (err) + { + log_error ("signing failed: %s\n", gpg_strerror (err)); + goto leave; + } + + if (DBG_CRYPTO) + gcry_log_debugsxp ("rslt", s_sig); + } + + /* Check that the signature verification worked and nothing is + * fooling us e.g. by a bug in the signature create code or by + * deliberately introduced faults. Because Libgcrypt 1.7 does this + * for RSA internally there is no need to do it here again. */ + if (check_signature) + { + gcry_sexp_t sexp_key = s_pkey? s_pkey: s_skey; + + if (s_hash == NULL) + { + if (ctrl->digest.algo == MD_USER_TLS_MD5SHA1) + err = do_encode_raw_pkcs1 (data, datalen, + gcry_pk_get_nbits (sexp_key), &s_hash); + else + err = do_encode_md (data, datalen, ctrl->digest.algo, &s_hash, + ctrl->digest.raw_value); + } + + if (!err) + err = gcry_pk_verify (s_sig, s_hash, sexp_key); + + if (err) + { + log_error (_("checking created signature failed: %s\n"), + gpg_strerror (err)); + gcry_sexp_release (s_sig); + s_sig = NULL; + } + } + + leave: + + *signature_sexp = s_sig; + + gcry_sexp_release (s_pkey); + gcry_sexp_release (s_skey); + gcry_sexp_release (s_hash); + xfree (shadow_info); + + return err; +} + + +/* SIGN whatever information we have accumulated in CTRL and write it + * back to OUTFP. If a CACHE_NONCE is given that cache item is first + * tried to get a passphrase. */ +gpg_error_t +agent_pksign (ctrl_t ctrl, const char *cache_nonce, const char *desc_text, + membuf_t *outbuf, cache_mode_t cache_mode) +{ + gpg_error_t err; + gcry_sexp_t s_sig = NULL; + char *buf = NULL; + size_t len = 0; + + err = agent_pksign_do (ctrl, cache_nonce, desc_text, &s_sig, cache_mode, + NULL, NULL, 0); + if (err) + goto leave; + + len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, NULL, 0); + log_assert (len); + buf = xtrymalloc (len); + if (!buf) + { + err = gpg_error_from_syserror (); + goto leave; + } + len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, buf, len); + log_assert (len); + put_membuf (outbuf, buf, len); + + leave: + gcry_sexp_release (s_sig); + xfree (buf); + + return err; +} |