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gnupg/sm/decrypt.c
Werner Koch 68b857df13
sm: Allow decryption using dhSinglePass-stdDH-sha1kdf-scheme. 
* sm/decrypt.c (ecdh_decrypt): Support
dhSinglePass-stdDH-sha1kdf-scheme.  Factor key derive code out to ...
(ecdh_derive_kek): new global function.  Allow for hashs shorter than
the key.
(hash_ecc_cms_shared_info): Make file-only.
* sm/encrypt.c (ecdh_encrypt): Replace derive code by a call to the
new ecdh_derive_kek.  Add test code to create data using
dhSinglePass-stdDH-sha1kdf-scheme.
* sm/gpgsm.h (opt): Add member force_ecdh_sha1kdf.
* sm/gpgsm.c: Add option --debug-force-ecdh-sha1kdf.
--

I did some test against

  Governikus_Signer:       2.9.2.0
  MCard security Provider: 2.4.0
  Algorithm catalog from:  05.12.2019

using a Signature Card v2.0 and a nistp256 certificate.  Encrypting
with Governikus used the stdDH-sha1kdf scheme which we can now
decrypt.  Encrypting with GPGSM uses for that curve the recommended
scheme sha256kdf but Governikus was not able to decrypt this (no
usable error message).  Encrypting using stdDH-sha1kdf with GPGSM by
using the new --debug-force-ecdh-sha1kdf option showed that
Governikus was able to decrypt this.

FWIW: RFC5753 (Use of Elliptic Curve Cryptography (ECC) Algorithms)
has this requirement:

   Implementations that support EnvelopedData with the
   ephemeral-static ECDH standard primitive:

   - MUST support the dhSinglePass-stdDH-sha256kdf-scheme key
     agreement algorithm, the id-aes128-wrap key wrap algorithm, and
     the id-aes128-cbc content encryption algorithm; and

which Governikus seems not to fulfill.

GnuPG-bug-id: 4098
Signed-off-by: Werner Koch <wk@gnupg.org>
2020-05-08 18:08:50 +02:00

1037 lines
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/* decrypt.c - Decrypt a message
* Copyright (C) 2001, 2003, 2010 Free Software Foundation, Inc.
* Copyright (C) 2001-2019 Werner Koch
* Copyright (C) 2015-2020 g10 Code GmbH
*
* 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/>.
* SPDX-License-Identifier: GPL-3.0-or-later
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <assert.h>
#include "gpgsm.h"
#include <gcrypt.h>
#include <ksba.h>
#include "keydb.h"
#include "../common/i18n.h"
#include "../common/tlv.h"
#include "../common/compliance.h"
struct decrypt_filter_parm_s
{
int algo;
int mode;
int blklen;
gcry_cipher_hd_t hd;
char iv[16];
size_t ivlen;
int any_data; /* did we push anything through the filter at all? */
unsigned char lastblock[16]; /* to strip the padding we have to
keep this one */
char helpblock[16]; /* needed because there is no block buffering in
libgcrypt (yet) */
int helpblocklen;
};
/* Return the hash algorithm's algo id from its name given in the
* non-null termnated string in (buffer,buflen). Returns 0 on failure
* or if the algo is not known. */
static char *
string_from_gcry_buffer (gcry_buffer_t *buffer)
{
char *string;
string = xtrymalloc (buffer->len + 1);
if (!string)
return NULL;
memcpy (string, buffer->data, buffer->len);
string[buffer->len] = 0;
return string;
}
/* Helper to construct and hash the
* ECC-CMS-SharedInfo ::= SEQUENCE {
* keyInfo AlgorithmIdentifier,
* entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL,
* suppPubInfo [2] EXPLICIT OCTET STRING }
* as described in RFC-5753, 7.2. */
static gpg_error_t
hash_ecc_cms_shared_info (gcry_md_hd_t hash_hd, const char *wrap_algo_str,
unsigned int keylen,
const void *ukm, unsigned int ukmlen)
{
gpg_error_t err;
void *p;
unsigned char *oid;
size_t n, oidlen, toidlen, tkeyinfo, tukmlen, tsupppubinfo;
unsigned char keylenbuf[6];
membuf_t mb = MEMBUF_ZERO;
err = ksba_oid_from_str (wrap_algo_str, &oid, &oidlen);
if (err)
return err;
toidlen = get_tlv_length (CLASS_UNIVERSAL, TAG_OBJECT_ID, 0, oidlen);
tkeyinfo = get_tlv_length (CLASS_UNIVERSAL, TAG_SEQUENCE, 1, toidlen);
tukmlen = ukm? get_tlv_length (CLASS_CONTEXT, 0, 1, ukmlen) : 0;
keylen *= 8;
keylenbuf[0] = TAG_OCTET_STRING;
keylenbuf[1] = 4;
keylenbuf[2] = (keylen >> 24);
keylenbuf[3] = (keylen >> 16);
keylenbuf[4] = (keylen >> 8);
keylenbuf[5] = keylen;
tsupppubinfo = get_tlv_length (CLASS_CONTEXT, 2, 1, sizeof keylenbuf);
put_tlv_to_membuf (&mb, CLASS_UNIVERSAL, TAG_SEQUENCE, 1,
tkeyinfo + tukmlen + tsupppubinfo);
put_tlv_to_membuf (&mb, CLASS_UNIVERSAL, TAG_SEQUENCE, 1,
toidlen);
put_tlv_to_membuf (&mb, CLASS_UNIVERSAL, TAG_OBJECT_ID, 0, oidlen);
put_membuf (&mb, oid, oidlen);
ksba_free (oid);
if (ukm)
{
put_tlv_to_membuf (&mb, CLASS_CONTEXT, 0, 1, ukmlen);
put_membuf (&mb, ukm, ukmlen);
}
put_tlv_to_membuf (&mb, CLASS_CONTEXT, 2, 1, sizeof keylenbuf);
put_membuf (&mb, keylenbuf, sizeof keylenbuf);
p = get_membuf (&mb, &n);
if (!p)
return gpg_error_from_syserror ();
gcry_md_write (hash_hd, p, n);
xfree (p);
return 0;
}
/* Derive a KEK (key wrapping key) using (SECRET,SECRETLEN), an
* optional (UKM,ULMLEN), the wrap algorithm WRAP_ALGO_STR in decimal
* dotted form, and the hash algorithm HASH_ALGO. On success a key of
* length KEYLEN is stored at KEY. */
gpg_error_t
ecdh_derive_kek (unsigned char *key, unsigned int keylen,
int hash_algo, const char *wrap_algo_str,
const void *secret, unsigned int secretlen,
const void *ukm, unsigned int ukmlen)
{
gpg_error_t err = 0;
unsigned int hashlen;
gcry_md_hd_t hash_hd;
unsigned char counter;
unsigned int n, ncopy;
hashlen = gcry_md_get_algo_dlen (hash_algo);
if (!hashlen)
return gpg_error (GPG_ERR_INV_ARG);
err = gcry_md_open (&hash_hd, hash_algo, 0);
if (err)
return err;
/* According to SEC1 3.6.1 we should check that
* SECRETLEN + UKMLEN + 4 < maxhashlen
* However, we have no practical limit on the hash length and thus
* there is no point in checking this. The second check that
* KEYLEN < hashlen*(2^32-1)
* is obviously also not needed.
*/
for (n=0, counter=1; n < keylen; counter++)
{
if (counter > 1)
gcry_md_reset (hash_hd);
gcry_md_write (hash_hd, secret, secretlen);
gcry_md_write (hash_hd, "\x00\x00\x00", 3); /* MSBs of counter */
gcry_md_write (hash_hd, &counter, 1);
err = hash_ecc_cms_shared_info (hash_hd, wrap_algo_str, keylen,
ukm, ukmlen);
if (err)
break;
gcry_md_final (hash_hd);
if (n + hashlen > keylen)
ncopy = keylen - n;
else
ncopy = hashlen;
memcpy (key+n, gcry_md_read (hash_hd, 0), ncopy);
n += ncopy;
}
gcry_md_close (hash_hd);
return err;
}
/* This function will modify SECRET. NBITS is the size of the curve
* which which we took from the certificate. */
static gpg_error_t
ecdh_decrypt (unsigned char *secret, size_t secretlen,
unsigned int nbits, gcry_sexp_t enc_val,
unsigned char **r_result, unsigned int *r_resultlen)
{
gpg_error_t err;
gcry_buffer_t ioarray[4] = { {0}, {0}, {0}, {0} };
char *encr_algo_str = NULL;
char *wrap_algo_str = NULL;
int hash_algo, cipher_algo;
const unsigned char *ukm; /* Alias for ioarray[2]. */
unsigned int ukmlen;
const unsigned char *data; /* Alias for ioarray[3]. */
unsigned int datalen;
unsigned int keylen;
unsigned char key[32];
gcry_cipher_hd_t cipher_hd = NULL;
unsigned char *result = NULL;
unsigned int resultlen;
*r_resultlen = 0;
*r_result = NULL;
/* Extract X from SECRET; this is the actual secret. Unless a
* smartcard diretcly returns X, it must be in the format of:
*
* 04 || X || Y
* 40 || X
* 41 || X
*/
if (secretlen < 2)
return gpg_error (GPG_ERR_BAD_DATA);
if (secretlen == (nbits+7)/8)
; /* Matches curve length - this is already the X coordinate. */
else if (*secret == 0x04)
{
secretlen--;
memmove (secret, secret+1, secretlen);
if ((secretlen & 1))
return gpg_error (GPG_ERR_BAD_DATA);
secretlen /= 2;
}
else if (*secret == 0x40 || *secret == 0x41)
{
secretlen--;
memmove (secret, secret+1, secretlen);
}
else
return gpg_error (GPG_ERR_BAD_DATA);
if (!secretlen)
return gpg_error (GPG_ERR_BAD_DATA);
if (DBG_CRYPTO)
log_printhex (secret, secretlen, "ECDH X ..:");
/* We have now the shared secret bytes in (SECRET,SECRETLEN). Now
* we will compute the KEK using a value dervied from the secret
* bytes. */
err = gcry_sexp_extract_param (enc_val, "enc-val",
"&'encr-algo''wrap-algo''ukm'?s",
ioarray+0, ioarray+1,
ioarray+2, ioarray+3, NULL);
if (err)
{
log_error ("extracting ECDH parameter failed: %s\n", gpg_strerror (err));
goto leave;
}
encr_algo_str = string_from_gcry_buffer (ioarray);
if (!encr_algo_str)
{
err = gpg_error_from_syserror ();
goto leave;
}
wrap_algo_str = string_from_gcry_buffer (ioarray+1);
if (!wrap_algo_str)
{
err = gpg_error_from_syserror ();
goto leave;
}
ukm = ioarray[2].data;
ukmlen = ioarray[2].len;
data = ioarray[3].data;
datalen = ioarray[3].len;
/* Check parameters. */
if (DBG_CRYPTO)
{
log_debug ("encr_algo: %s\n", encr_algo_str);
log_debug ("wrap_algo: %s\n", wrap_algo_str);
log_printhex (ukm, ukmlen, "ukm .....:");
log_printhex (data, datalen, "data ....:");
}
if (!strcmp (encr_algo_str, "1.3.132.1.11.1"))
{
/* dhSinglePass-stdDH-sha256kdf-scheme */
hash_algo = GCRY_MD_SHA256;
}
else if (!strcmp (encr_algo_str, "1.3.132.1.11.2"))
{
/* dhSinglePass-stdDH-sha384kdf-scheme */
hash_algo = GCRY_MD_SHA384;
}
else if (!strcmp (encr_algo_str, "1.3.132.1.11.3"))
{
/* dhSinglePass-stdDH-sha512kdf-scheme */
hash_algo = GCRY_MD_SHA512;
}
else if (!strcmp (encr_algo_str, "1.3.133.16.840.63.0.2"))
{
/* dhSinglePass-stdDH-sha1kdf-scheme */
hash_algo = GCRY_MD_SHA1;
}
else
{
err = gpg_error (GPG_ERR_PUBKEY_ALGO);
goto leave;
}
if (!strcmp (wrap_algo_str, "2.16.840.1.101.3.4.1.5"))
{
cipher_algo = GCRY_CIPHER_AES128;
keylen = 16;
}
else if (!strcmp (wrap_algo_str, "2.16.840.1.101.3.4.1.25"))
{
cipher_algo = GCRY_CIPHER_AES192;
keylen = 24;
}
else if (!strcmp (wrap_algo_str, "2.16.840.1.101.3.4.1.45"))
{
cipher_algo = GCRY_CIPHER_AES256;
keylen = 32;
}
else
{
err = gpg_error (GPG_ERR_PUBKEY_ALGO);
goto leave;
}
err = ecdh_derive_kek (key, keylen, hash_algo, wrap_algo_str,
secret, secretlen, ukm, ukmlen);
if (err)
goto leave;
if (DBG_CRYPTO)
log_printhex (key, keylen, "KEK .....:");
/* Unwrap the key. */
if ((datalen % 8) || datalen < 16)
{
log_error ("can't use a shared secret of %u bytes for ecdh\n", datalen);
err = gpg_error (GPG_ERR_BAD_DATA);
goto leave;
}
resultlen = datalen - 8;
result = xtrymalloc_secure (resultlen);
if (!result)
{
err = gpg_error_from_syserror ();
goto leave;
}
err = gcry_cipher_open (&cipher_hd, cipher_algo, GCRY_CIPHER_MODE_AESWRAP, 0);
if (err)
{
log_error ("ecdh failed to initialize AESWRAP: %s\n", gpg_strerror (err));
goto leave;
}
err = gcry_cipher_setkey (cipher_hd, key, keylen);
wipememory (key, sizeof key);
if (err)
{
log_error ("ecdh failed in gcry_cipher_setkey: %s\n", gpg_strerror (err));
goto leave;
}
err = gcry_cipher_decrypt (cipher_hd, result, resultlen, data, datalen);
if (err)
{
log_error ("ecdh failed in gcry_cipher_decrypt: %s\n",gpg_strerror (err));
goto leave;
}
*r_resultlen = resultlen;
*r_result = result;
result = NULL;
leave:
if (result)
{
wipememory (result, resultlen);
xfree (result);
}
gcry_cipher_close (cipher_hd);
xfree (encr_algo_str);
xfree (wrap_algo_str);
xfree (ioarray[0].data);
xfree (ioarray[1].data);
xfree (ioarray[2].data);
xfree (ioarray[3].data);
return err;
}
/* Decrypt the session key and fill in the parm structure. The
algo and the IV is expected to be already in PARM. */
static int
prepare_decryption (ctrl_t ctrl, const char *hexkeygrip,
int pk_algo, unsigned int nbits, const char *desc,
ksba_const_sexp_t enc_val,
struct decrypt_filter_parm_s *parm)
{
char *seskey = NULL;
size_t n, seskeylen;
int rc;
if (DBG_CRYPTO)
log_printcanon ("decrypting:", enc_val, 0);
rc = gpgsm_agent_pkdecrypt (ctrl, hexkeygrip, desc, enc_val,
&seskey, &seskeylen);
if (rc)
{
log_error ("error decrypting session key: %s\n", gpg_strerror (rc));
goto leave;
}
if (DBG_CRYPTO)
log_printhex (seskey, seskeylen, "DEK frame:");
n=0;
if (pk_algo == GCRY_PK_ECC)
{
gcry_sexp_t s_enc_val;
unsigned char *decrypted;
unsigned int decryptedlen;
rc = gcry_sexp_sscan (&s_enc_val, NULL, enc_val,
gcry_sexp_canon_len (enc_val, 0, NULL, NULL));
if (rc)
goto leave;
rc = ecdh_decrypt (seskey, seskeylen, nbits, s_enc_val,
&decrypted, &decryptedlen);
gcry_sexp_release (s_enc_val);
if (rc)
goto leave;
xfree (seskey);
seskey = decrypted;
seskeylen = decryptedlen;
}
else if (seskeylen == 32 || seskeylen == 24 || seskeylen == 16)
{
/* Smells like an AES-128, 3-DES, or AES-256 key. This might
* happen because a SC has already done the unpacking. A better
* solution would be to test for this only after we triggered
* the GPG_ERR_INV_SESSION_KEY. */
}
else
{
if (n + 7 > seskeylen )
{
rc = gpg_error (GPG_ERR_INV_SESSION_KEY);
goto leave;
}
/* FIXME: Actually the leading zero is required but due to the way
we encode the output in libgcrypt as an MPI we are not able to
encode that leading zero. However, when using a Smartcard we are
doing it the right way and therefore we have to skip the zero. This
should be fixed in gpg-agent of course. */
if (!seskey[n])
n++;
if (seskey[n] != 2 ) /* Wrong block type version. */
{
rc = gpg_error (GPG_ERR_INV_SESSION_KEY);
goto leave;
}
for (n++; n < seskeylen && seskey[n]; n++) /* Skip the random bytes. */
;
n++; /* and the zero byte */
if (n >= seskeylen )
{
rc = gpg_error (GPG_ERR_INV_SESSION_KEY);
goto leave;
}
}
if (DBG_CRYPTO)
log_printhex (seskey+n, seskeylen-n, "CEK .....:");
if (opt.verbose)
log_info (_("%s.%s encrypted data\n"),
gcry_cipher_algo_name (parm->algo),
cipher_mode_to_string (parm->mode));
rc = gcry_cipher_open (&parm->hd, parm->algo, parm->mode, 0);
if (rc)
{
log_error ("error creating decryptor: %s\n", gpg_strerror (rc));
goto leave;
}
rc = gcry_cipher_setkey (parm->hd, seskey+n, seskeylen-n);
if (gpg_err_code (rc) == GPG_ERR_WEAK_KEY)
{
log_info (_("WARNING: message was encrypted with "
"a weak key in the symmetric cipher.\n"));
rc = 0;
}
if (rc)
{
log_error("key setup failed: %s\n", gpg_strerror(rc) );
goto leave;
}
gcry_cipher_setiv (parm->hd, parm->iv, parm->ivlen);
leave:
xfree (seskey);
return rc;
}
/* This function is called by the KSBA writer just before the actual
write is done. The function must take INLEN bytes from INBUF,
decrypt it and store it inoutbuf which has a maximum size of
maxoutlen. The valid bytes in outbuf should be return in outlen.
Due to different buffer sizes or different length of input and
output, it may happen that fewer bytes are processed or fewer bytes
are written. */
static gpg_error_t
decrypt_filter (void *arg,
const void *inbuf, size_t inlen, size_t *inused,
void *outbuf, size_t maxoutlen, size_t *outlen)
{
struct decrypt_filter_parm_s *parm = arg;
int blklen = parm->blklen;
size_t orig_inlen = inlen;
/* fixme: Should we issue an error when we have not seen one full block? */
if (!inlen)
return gpg_error (GPG_ERR_BUG);
if (maxoutlen < 2*parm->blklen)
return gpg_error (GPG_ERR_BUG);
/* Make some space because we will later need an extra block at the end. */
maxoutlen -= blklen;
if (parm->helpblocklen)
{
int i, j;
for (i=parm->helpblocklen,j=0; i < blklen && j < inlen; i++, j++)
parm->helpblock[i] = ((const char*)inbuf)[j];
inlen -= j;
if (blklen > maxoutlen)
return gpg_error (GPG_ERR_BUG);
if (i < blklen)
{
parm->helpblocklen = i;
*outlen = 0;
}
else
{
parm->helpblocklen = 0;
if (parm->any_data)
{
memcpy (outbuf, parm->lastblock, blklen);
*outlen =blklen;
}
else
*outlen = 0;
gcry_cipher_decrypt (parm->hd, parm->lastblock, blklen,
parm->helpblock, blklen);
parm->any_data = 1;
}
*inused = orig_inlen - inlen;
return 0;
}
if (inlen > maxoutlen)
inlen = maxoutlen;
if (inlen % blklen)
{ /* store the remainder away */
parm->helpblocklen = inlen%blklen;
inlen = inlen/blklen*blklen;
memcpy (parm->helpblock, (const char*)inbuf+inlen, parm->helpblocklen);
}
*inused = inlen + parm->helpblocklen;
if (inlen)
{
assert (inlen >= blklen);
if (parm->any_data)
{
gcry_cipher_decrypt (parm->hd, (char*)outbuf+blklen, inlen,
inbuf, inlen);
memcpy (outbuf, parm->lastblock, blklen);
memcpy (parm->lastblock,(char*)outbuf+inlen, blklen);
*outlen = inlen;
}
else
{
gcry_cipher_decrypt (parm->hd, outbuf, inlen, inbuf, inlen);
memcpy (parm->lastblock, (char*)outbuf+inlen-blklen, blklen);
*outlen = inlen - blklen;
parm->any_data = 1;
}
}
else
*outlen = 0;
return 0;
}
/* Perform a decrypt operation. */
int
gpgsm_decrypt (ctrl_t ctrl, int in_fd, estream_t out_fp)
{
int rc;
gnupg_ksba_io_t b64reader = NULL;
gnupg_ksba_io_t b64writer = NULL;
ksba_reader_t reader;
ksba_writer_t writer;
ksba_cms_t cms = NULL;
ksba_stop_reason_t stopreason;
KEYDB_HANDLE kh;
int recp;
estream_t in_fp = NULL;
struct decrypt_filter_parm_s dfparm;
memset (&dfparm, 0, sizeof dfparm);
audit_set_type (ctrl->audit, AUDIT_TYPE_DECRYPT);
kh = keydb_new ();
if (!kh)
{
log_error (_("failed to allocate keyDB handle\n"));
rc = gpg_error (GPG_ERR_GENERAL);
goto leave;
}
in_fp = es_fdopen_nc (in_fd, "rb");
if (!in_fp)
{
rc = gpg_error_from_syserror ();
log_error ("fdopen() failed: %s\n", strerror (errno));
goto leave;
}
rc = gnupg_ksba_create_reader
(&b64reader, ((ctrl->is_pem? GNUPG_KSBA_IO_PEM : 0)
| (ctrl->is_base64? GNUPG_KSBA_IO_BASE64 : 0)
| (ctrl->autodetect_encoding? GNUPG_KSBA_IO_AUTODETECT : 0)),
in_fp, &reader);
if (rc)
{
log_error ("can't create reader: %s\n", gpg_strerror (rc));
goto leave;
}
rc = gnupg_ksba_create_writer
(&b64writer, ((ctrl->create_pem? GNUPG_KSBA_IO_PEM : 0)
| (ctrl->create_base64? GNUPG_KSBA_IO_BASE64 : 0)),
ctrl->pem_name, out_fp, &writer);
if (rc)
{
log_error ("can't create writer: %s\n", gpg_strerror (rc));
goto leave;
}
rc = ksba_cms_new (&cms);
if (rc)
goto leave;
rc = ksba_cms_set_reader_writer (cms, reader, writer);
if (rc)
{
log_error ("ksba_cms_set_reader_writer failed: %s\n",
gpg_strerror (rc));
goto leave;
}
audit_log (ctrl->audit, AUDIT_SETUP_READY);
/* Parser loop. */
do
{
rc = ksba_cms_parse (cms, &stopreason);
if (rc)
{
log_error ("ksba_cms_parse failed: %s\n", gpg_strerror (rc));
goto leave;
}
if (stopreason == KSBA_SR_BEGIN_DATA
|| stopreason == KSBA_SR_DETACHED_DATA)
{
int algo, mode;
const char *algoid;
int any_key = 0;
int is_de_vs; /* Computed compliance with CO_DE_VS. */
audit_log (ctrl->audit, AUDIT_GOT_DATA);
algoid = ksba_cms_get_content_oid (cms, 2/* encryption algo*/);
algo = gcry_cipher_map_name (algoid);
mode = gcry_cipher_mode_from_oid (algoid);
if (!algo || !mode)
{
rc = gpg_error (GPG_ERR_UNSUPPORTED_ALGORITHM);
log_error ("unsupported algorithm '%s'\n", algoid? algoid:"?");
if (algoid && !strcmp (algoid, "1.2.840.113549.3.2"))
log_info (_("(this is the RC2 algorithm)\n"));
else if (!algoid)
log_info (_("(this does not seem to be an encrypted"
" message)\n"));
{
char numbuf[50];
sprintf (numbuf, "%d", rc);
gpgsm_status2 (ctrl, STATUS_ERROR, "decrypt.algorithm",
numbuf, algoid?algoid:"?", NULL);
audit_log_s (ctrl->audit, AUDIT_BAD_DATA_CIPHER_ALGO, algoid);
}
/* If it seems that this is not an encrypted message we
return a more sensible error code. */
if (!algoid)
rc = gpg_error (GPG_ERR_NO_DATA);
goto leave;
}
/* Check compliance. */
if (! gnupg_cipher_is_allowed (opt.compliance, 0, algo, mode))
{
log_error (_("cipher algorithm '%s'"
" may not be used in %s mode\n"),
gcry_cipher_algo_name (algo),
gnupg_compliance_option_string (opt.compliance));
rc = gpg_error (GPG_ERR_CIPHER_ALGO);
goto leave;
}
/* For CMS, CO_DE_VS demands CBC mode. */
is_de_vs = gnupg_cipher_is_compliant (CO_DE_VS, algo, mode);
audit_log_i (ctrl->audit, AUDIT_DATA_CIPHER_ALGO, algo);
dfparm.algo = algo;
dfparm.mode = mode;
dfparm.blklen = gcry_cipher_get_algo_blklen (algo);
if (dfparm.blklen > sizeof (dfparm.helpblock))
return gpg_error (GPG_ERR_BUG);
rc = ksba_cms_get_content_enc_iv (cms,
dfparm.iv,
sizeof (dfparm.iv),
&dfparm.ivlen);
if (rc)
{
log_error ("error getting IV: %s\n", gpg_strerror (rc));
goto leave;
}
for (recp=0; !any_key; recp++)
{
char *issuer;
ksba_sexp_t serial;
ksba_sexp_t enc_val;
char *hexkeygrip = NULL;
char *pkalgostr = NULL;
char *pkfpr = NULL;
char *desc = NULL;
char kidbuf[16+1];
int tmp_rc;
ksba_cert_t cert = NULL;
unsigned int nbits;
int pk_algo = 0;
*kidbuf = 0;
tmp_rc = ksba_cms_get_issuer_serial (cms, recp, &issuer, &serial);
if (tmp_rc == -1 && recp)
break; /* no more recipients */
audit_log_i (ctrl->audit, AUDIT_NEW_RECP, recp);
if (tmp_rc)
log_error ("recp %d - error getting info: %s\n",
recp, gpg_strerror (tmp_rc));
else
{
if (opt.verbose)
{
log_info ("recp %d - issuer: '%s'\n",
recp, issuer? issuer:"[NONE]");
log_info ("recp %d - serial: ", recp);
gpgsm_dump_serial (serial);
log_printf ("\n");
}
if (ctrl->audit)
{
char *tmpstr = gpgsm_format_sn_issuer (serial, issuer);
audit_log_s (ctrl->audit, AUDIT_RECP_NAME, tmpstr);
xfree (tmpstr);
}
keydb_search_reset (kh);
rc = keydb_search_issuer_sn (ctrl, kh, issuer, serial);
if (rc)
{
log_error ("failed to find the certificate: %s\n",
gpg_strerror(rc));
goto oops;
}
rc = keydb_get_cert (kh, &cert);
if (rc)
{
log_error ("failed to get cert: %s\n", gpg_strerror (rc));
goto oops;
}
/* Print the ENC_TO status line. Note that we can
do so only if we have the certificate. This is
in contrast to gpg where the keyID is commonly
included in the encrypted messages. It is too
cumbersome to retrieve the used algorithm, thus
we don't print it for now. We also record the
keyid for later use. */
{
unsigned long kid[2];
kid[0] = gpgsm_get_short_fingerprint (cert, kid+1);
snprintf (kidbuf, sizeof kidbuf, "%08lX%08lX",
kid[1], kid[0]);
gpgsm_status2 (ctrl, STATUS_ENC_TO,
kidbuf, "0", "0", NULL);
}
/* Put the certificate into the audit log. */
audit_log_cert (ctrl->audit, AUDIT_SAVE_CERT, cert, 0);
/* Just in case there is a problem with the own
certificate we print this message - should never
happen of course */
rc = gpgsm_cert_use_decrypt_p (cert);
if (rc)
{
char numbuf[50];
sprintf (numbuf, "%d", rc);
gpgsm_status2 (ctrl, STATUS_ERROR, "decrypt.keyusage",
numbuf, NULL);
rc = 0;
}
hexkeygrip = gpgsm_get_keygrip_hexstring (cert);
desc = gpgsm_format_keydesc (cert);
pkfpr = gpgsm_get_fingerprint_hexstring (cert, GCRY_MD_SHA1);
pkalgostr = gpgsm_pubkey_algo_string (cert, NULL);
pk_algo = gpgsm_get_key_algo_info (cert, &nbits);
if (!opt.quiet)
log_info (_("encrypted to %s key %s\n"), pkalgostr, pkfpr);
/* Check compliance. */
if (!gnupg_pk_is_allowed (opt.compliance,
PK_USE_DECRYPTION,
pk_algo, NULL, nbits, NULL))
{
char kidstr[10+1];
snprintf (kidstr, sizeof kidstr, "0x%08lX",
gpgsm_get_short_fingerprint (cert, NULL));
log_info (_("key %s is not suitable for decryption"
" in %s mode\n"),
kidstr,
gnupg_compliance_option_string(opt.compliance));
rc = gpg_error (GPG_ERR_PUBKEY_ALGO);
goto oops;
}
/* Check that all certs are compliant with CO_DE_VS. */
is_de_vs = (is_de_vs
&& gnupg_pk_is_compliant (CO_DE_VS, pk_algo,
NULL, nbits, NULL));
oops:
if (rc)
{
/* We cannot check compliance of certs that we
* don't have. */
is_de_vs = 0;
}
xfree (issuer);
xfree (serial);
ksba_cert_release (cert);
}
if (!hexkeygrip || !pk_algo)
;
else if (!(enc_val = ksba_cms_get_enc_val (cms, recp)))
log_error ("recp %d - error getting encrypted session key\n",
recp);
else
{
rc = prepare_decryption (ctrl, hexkeygrip, pk_algo, nbits,
desc, enc_val, &dfparm);
xfree (enc_val);
if (rc)
{
log_info ("decrypting session key failed: %s\n",
gpg_strerror (rc));
if (gpg_err_code (rc) == GPG_ERR_NO_SECKEY && *kidbuf)
gpgsm_status2 (ctrl, STATUS_NO_SECKEY, kidbuf, NULL);
}
else
{ /* setup the bulk decrypter */
any_key = 1;
ksba_writer_set_filter (writer,
decrypt_filter,
&dfparm);
if (is_de_vs)
gpgsm_status (ctrl, STATUS_DECRYPTION_COMPLIANCE_MODE,
gnupg_status_compliance_flag (CO_DE_VS));
}
audit_log_ok (ctrl->audit, AUDIT_RECP_RESULT, rc);
}
xfree (pkalgostr);
xfree (pkfpr);
xfree (hexkeygrip);
xfree (desc);
}
/* If we write an audit log add the unused recipients to the
log as well. */
if (ctrl->audit && any_key)
{
for (;; recp++)
{
char *issuer;
ksba_sexp_t serial;
int tmp_rc;
tmp_rc = ksba_cms_get_issuer_serial (cms, recp,
&issuer, &serial);
if (tmp_rc == -1)
break; /* no more recipients */
audit_log_i (ctrl->audit, AUDIT_NEW_RECP, recp);
if (tmp_rc)
log_error ("recp %d - error getting info: %s\n",
recp, gpg_strerror (tmp_rc));
else
{
char *tmpstr = gpgsm_format_sn_issuer (serial, issuer);
audit_log_s (ctrl->audit, AUDIT_RECP_NAME, tmpstr);
xfree (tmpstr);
xfree (issuer);
xfree (serial);
}
}
}
if (!any_key)
{
if (!rc)
rc = gpg_error (GPG_ERR_NO_SECKEY);
goto leave;
}
}
else if (stopreason == KSBA_SR_END_DATA)
{
ksba_writer_set_filter (writer, NULL, NULL);
if (dfparm.any_data)
{ /* write the last block with padding removed */
int i, npadding = dfparm.lastblock[dfparm.blklen-1];
if (!npadding || npadding > dfparm.blklen)
{
log_error ("invalid padding with value %d\n", npadding);
rc = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
rc = ksba_writer_write (writer,
dfparm.lastblock,
dfparm.blklen - npadding);
if (rc)
goto leave;
for (i=dfparm.blklen - npadding; i < dfparm.blklen; i++)
{
if (dfparm.lastblock[i] != npadding)
{
log_error ("inconsistent padding\n");
rc = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
}
}
}
}
while (stopreason != KSBA_SR_READY);
rc = gnupg_ksba_finish_writer (b64writer);
if (rc)
{
log_error ("write failed: %s\n", gpg_strerror (rc));
goto leave;
}
gpgsm_status (ctrl, STATUS_DECRYPTION_OKAY, NULL);
leave:
audit_log_ok (ctrl->audit, AUDIT_DECRYPTION_RESULT, rc);
if (rc)
{
gpgsm_status (ctrl, STATUS_DECRYPTION_FAILED, NULL);
log_error ("message decryption failed: %s <%s>\n",
gpg_strerror (rc), gpg_strsource (rc));
}
ksba_cms_release (cms);
gnupg_ksba_destroy_reader (b64reader);
gnupg_ksba_destroy_writer (b64writer);
keydb_release (kh);
es_fclose (in_fp);
if (dfparm.hd)
gcry_cipher_close (dfparm.hd);
return rc;
}
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