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/* 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 <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. */
gpg_error_t
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;
gpg_error_t err = 0;
int no_shadow_info = 0;
char *buf = NULL;
size_t len;
*r_padding = -1;
if (!ctrl->have_keygrip)
{
log_error ("speculative decryption not yet supported\n");
err = gpg_error (GPG_ERR_NO_SECKEY);
goto leave;
}
err = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
if (err)
{
log_error ("failed to convert ciphertext: %s\n", gpg_strerror (err));
err = gpg_error (GPG_ERR_INV_DATA);
goto leave;
}
if (DBG_CRYPTO)
{
log_printhex (ctrl->keygrip, 20, "keygrip:");
log_printhex (ciphertext, ciphertextlen, "cipher: ");
}
err = agent_key_from_file (ctrl, NULL, desc_text,
NULL, &shadow_info,
CACHE_MODE_NORMAL, NULL, &s_skey, NULL, NULL);
if (gpg_err_code (err) == GPG_ERR_NO_SECKEY)
no_shadow_info = 1;
else if (err)
{
log_error ("failed to read the secret key\n");
goto leave;
}
if (shadow_info || no_shadow_info)
{ /* divert operation to the smartcard */
if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
{
err = gpg_error (GPG_ERR_INV_SEXP);
goto leave;
}
if (s_skey && agent_is_tpm2_key (s_skey))
err = divert_tpm2_pkdecrypt (ctrl, ciphertext, shadow_info,
&buf, &len, r_padding);
else
err = divert_pkdecrypt (ctrl, ctrl->keygrip, ciphertext,
&buf, &len, r_padding);
if (err)
{
/* We restore the original error (ie. no seckey) is no card
* has been found and we have no shadow key. This avoids a
* surprising "card removed" error code. */
if ((gpg_err_code (err) == GPG_ERR_CARD_REMOVED
|| gpg_err_code (err) == GPG_ERR_CARD_NOT_PRESENT)
&& no_shadow_info)
err = gpg_error (GPG_ERR_NO_SECKEY);
else
log_error ("smartcard decryption failed: %s\n", gpg_strerror (err));
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); */
/* } */
err = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
if (err)
{
log_error ("decryption failed: %s\n", gpg_strerror (err));
goto leave;
}
if (DBG_CRYPTO)
{
log_debug ("plain: ");
gcry_sexp_dump (s_plain);
}
len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
log_assert (len);
buf = xmalloc (len);
len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
log_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 err;
}
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