mirror of
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186 lines
5.0 KiB
C
186 lines
5.0 KiB
C
/* pksign.c - public key signing (well, acually using a secret key)
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* Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <config.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#include <assert.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include "agent.h"
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static int
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do_encode_md (const unsigned char *digest, size_t digestlen, int algo,
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unsigned int nbits, gcry_mpi_t *r_val)
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{
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int nframe = (nbits+7) / 8;
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byte *frame;
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int i, n;
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byte asn[100];
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size_t asnlen;
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asnlen = DIM(asn);
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if (gcry_md_algo_info (algo, GCRYCTL_GET_ASNOID, asn, &asnlen))
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{
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log_error ("no object identifier for algo %d\n", algo);
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return gpg_error (GPG_ERR_INTERNAL);
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}
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if (digestlen + asnlen + 4 > nframe )
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{
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log_error ("can't encode a %d bit MD into a %d bits frame\n",
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(int)(digestlen*8), (int)nbits);
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return gpg_error (GPG_ERR_INTERNAL);
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}
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/* We encode the MD in this way:
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*
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* 0 1 PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes)
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*
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* PAD consists of FF bytes.
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*/
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frame = xtrymalloc (nframe);
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if (!frame)
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return out_of_core ();
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n = 0;
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frame[n++] = 0;
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frame[n++] = 1; /* block type */
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i = nframe - digestlen - asnlen -3 ;
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assert ( i > 1 );
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memset ( frame+n, 0xff, i ); n += i;
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frame[n++] = 0;
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memcpy ( frame+n, asn, asnlen ); n += asnlen;
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memcpy ( frame+n, digest, digestlen ); n += digestlen;
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assert ( n == nframe );
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if (DBG_CRYPTO)
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log_printhex ("encoded hash:", frame, nframe);
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gcry_mpi_scan (r_val, GCRYMPI_FMT_USG, frame, &nframe);
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xfree (frame);
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return 0;
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}
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/* SIGN whatever information we have accumulated in CTRL and write it
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back to OUTFP. */
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int
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agent_pksign (CTRL ctrl, FILE *outfp, int ignore_cache)
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{
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gcry_sexp_t s_skey = NULL, s_hash = NULL, s_sig = NULL;
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gcry_mpi_t frame = NULL;
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unsigned char *shadow_info = NULL;
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int rc;
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char *buf = NULL;
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size_t len;
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if (!ctrl->have_keygrip)
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return gpg_error (GPG_ERR_NO_SECKEY);
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s_skey = agent_key_from_file (ctrl,
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ctrl->keygrip, &shadow_info, ignore_cache);
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if (!s_skey && !shadow_info)
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{
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log_error ("failed to read the secret key\n");
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rc = gpg_error (GPG_ERR_NO_SECKEY);
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goto leave;
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}
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if (!s_skey)
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{ /* divert operation to the smartcard */
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unsigned char *sigbuf;
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rc = divert_pksign (ctrl,
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ctrl->digest.value,
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ctrl->digest.valuelen,
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ctrl->digest.algo,
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shadow_info, &sigbuf);
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if (rc)
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{
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log_error ("smartcard signing failed: %s\n", gpg_strerror (rc));
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goto leave;
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}
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len = gcry_sexp_canon_len (sigbuf, 0, NULL, NULL);
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assert (len);
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buf = sigbuf;
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}
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else
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{ /* no smartcard, but a private key */
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/* put the hash into a sexp */
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rc = do_encode_md (ctrl->digest.value,
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ctrl->digest.valuelen,
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ctrl->digest.algo,
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gcry_pk_get_nbits (s_skey),
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&frame);
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if (rc)
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goto leave;
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if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
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BUG ();
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if (DBG_CRYPTO)
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{
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log_debug ("skey: ");
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gcry_sexp_dump (s_skey);
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}
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/* sign */
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rc = gcry_pk_sign (&s_sig, s_hash, s_skey);
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if (rc)
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{
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log_error ("signing failed: %s\n", gpg_strerror (rc));
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rc = map_gcry_err (rc);
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goto leave;
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}
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if (DBG_CRYPTO)
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{
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log_debug ("result: ");
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gcry_sexp_dump (s_sig);
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}
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len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, NULL, 0);
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assert (len);
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buf = xmalloc (len);
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len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, buf, len);
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assert (len);
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}
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/* FIXME: we must make sure that no buffering takes place or we are
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in full control of the buffer memory (easy to do) - should go
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into assuan. */
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fwrite (buf, 1, len, outfp);
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leave:
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gcry_sexp_release (s_skey);
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gcry_sexp_release (s_hash);
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gcry_sexp_release (s_sig);
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gcry_mpi_release (frame);
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xfree (buf);
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xfree (shadow_info);
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return rc;
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}
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