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gnupg/agent/pkdecrypt.c
James Bottomley 1a4a4a8f5f
agent: plumb in TPM handling
* agent/divert-tpm2.c: New.
* Makefile.am (gpg_agent_SOURCES): Add it.
* agent/command.c (do_one_keyinfo): Fake serialno for TPM.
(cmd_keytotpm): New.
(register_commands): Register KEYTOTPM command.
* agent/pkdecrypt.c (agent_pkdecrypt): Divert to TPM.
* agent/pksign.c (agent_pksign_do): Divert to TPM.

--
This code installs diversions for pksign and pkdecrypt to do the
operations via the TPM if a TPM shadowed key is present.  It also adds
an extra assuan command KEYTOTPM which moves an existing private key
to a TPM shadowed key.

The way TPM shadowing works is that the public and private key parts
are fed in to the TPM command TPM2_Import.  The output of this command
is a TPM specific public and private key data where the private key
data is symmetrically encrypted using a TPM internal key.  If this
physical TPM is ever lost or cleared, that TPM internal key will
likewise be lost and nothing will ever be able to read the private
key.  Once the import is done, the shadow information for the key is
updated to be a three part list consisting of the parent key (hard
coded to 81000001 which is the Microsoft preferred RSA incarnation of
the storage seed) and the public and private TPM data blobs.

Now when a TPM shadowed key is used, the data blobs must be loaded
into the TPM with TPM2_Load before any operation can be performed.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

- Added ChangeLog entries

Signed-off-by: Werner Koch <wk@gnupg.org>
2018-03-09 10:01:59 +01:00

151 lines
4.3 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;
}
if (agent_is_tpm2_key (s_skey))
rc = divert_tpm2_pkdecrypt (ctrl, desc_text, ciphertext, shadow_info,
&buf, &len, r_padding);
else
rc = divert_pkdecrypt (ctrl, desc_text, ciphertext, 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;
}