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gnupg/agent/pkdecrypt.c
Werner Koch 5d98f95aa9
gpg: Provide better diagnostic for replaced card keys.
* agent/divert-scd.c (divert_pksign): Add arg 'grip'.  Replace OPENPGP
key reference to keygrips.
(divert_pkdecrypt): Ditto.
* agent/protect.c (parse_shadow_info): Trim spaces.
* agent/pkdecrypt.c (agent_pkdecrypt): Pass the keygrip.
* agent/pksign.c (agent_pksign_do): Ditto.

* g10/mainproc.c (print_pkenc_list): Print extra info for an invalid
id error.
* g10/sign.c (do_sign): Ditto.
--

Using the keygrip instead of the identifier works on OpenPGP cards and
thus we use that to make sure that we are working on the right card.
For other cards we better don't do that to avoid regressions.  Those
other cards are also usually provided and do not allow to
self-generate the keys.

Note that old versions of the code (gpg 1.4) used the fingerprint as
additional check but that was eventually removed and now that we use
the keygrip all over the place, it is best to use this to identify a
key.

Signed-off-by: Werner Koch <wk@gnupg.org>
2020-11-13 16:06:59 +01:00

148 lines
4.2 KiB
C

/* pkdecrypt.c - public key decryption (well, actually using a secret key)
* Copyright (C) 2001, 2003 Free Software Foundation, Inc.
*
* 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"
/* DECRYPT the stuff in ciphertext which is expected to be a S-Exp.
Try to get the key from CTRL and write the decoded stuff back to
OUTFP. The padding information is stored at R_PADDING with -1
for not known. */
int
agent_pkdecrypt (ctrl_t ctrl, const char *desc_text,
const unsigned char *ciphertext, size_t ciphertextlen,
membuf_t *outbuf, int *r_padding)
{
gcry_sexp_t s_skey = NULL, s_cipher = NULL, s_plain = NULL;
unsigned char *shadow_info = NULL;
int rc;
char *buf = NULL;
size_t len;
*r_padding = -1;
if (!ctrl->have_keygrip)
{
log_error ("speculative decryption not yet supported\n");
rc = gpg_error (GPG_ERR_NO_SECKEY);
goto leave;
}
rc = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
if (rc)
{
log_error ("failed to convert ciphertext: %s\n", gpg_strerror (rc));
rc = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
if (DBG_CRYPTO)
{
log_printhex (ctrl->keygrip, 20, "keygrip:");
log_printhex (ciphertext, ciphertextlen, "cipher: ");
}
rc = agent_key_from_file (ctrl, NULL, desc_text,
ctrl->keygrip, &shadow_info,
CACHE_MODE_NORMAL, NULL, &s_skey, NULL);
if (rc)
{
if (gpg_err_code (rc) != GPG_ERR_NO_SECKEY)
log_error ("failed to read the secret key\n");
goto leave;
}
if (shadow_info)
{ /* divert operation to the smartcard */
if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
{
rc = gpg_error (GPG_ERR_INV_SEXP);
goto leave;
}
rc = divert_pkdecrypt (ctrl, desc_text, ciphertext,
ctrl->keygrip, shadow_info,
&buf, &len, r_padding);
if (rc)
{
log_error ("smartcard decryption failed: %s\n", gpg_strerror (rc));
goto leave;
}
put_membuf_printf (outbuf, "(5:value%u:", (unsigned int)len);
put_membuf (outbuf, buf, len);
put_membuf (outbuf, ")", 2);
}
else
{ /* No smartcard, but a private key */
/* if (DBG_CRYPTO ) */
/* { */
/* log_debug ("skey: "); */
/* gcry_sexp_dump (s_skey); */
/* } */
rc = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
if (rc)
{
log_error ("decryption failed: %s\n", gpg_strerror (rc));
goto leave;
}
if (DBG_CRYPTO)
{
log_debug ("plain: ");
gcry_sexp_dump (s_plain);
}
len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
assert (len);
buf = xmalloc (len);
len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
assert (len);
if (*buf == '(')
put_membuf (outbuf, buf, len);
else
{
/* Old style libgcrypt: This is only an S-expression
part. Turn it into a complete S-expression. */
put_membuf (outbuf, "(5:value", 8);
put_membuf (outbuf, buf, len);
put_membuf (outbuf, ")", 2);
}
}
leave:
gcry_sexp_release (s_skey);
gcry_sexp_release (s_plain);
gcry_sexp_release (s_cipher);
xfree (buf);
xfree (shadow_info);
return rc;
}