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592 lines
14 KiB
C
592 lines
14 KiB
C
/* encrypt.c - Encrypt a message
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* Copyright (C) 2001 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 <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <time.h>
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#include <assert.h>
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#include <gcrypt.h>
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#include <ksba.h>
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#include "gpgsm.h"
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#include "keydb.h"
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#include "i18n.h"
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struct dek_s {
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const char *algoid;
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int algo;
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GCRY_CIPHER_HD chd;
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char key[32];
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int keylen;
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char iv[32];
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int ivlen;
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};
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typedef struct dek_s *DEK;
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struct encrypt_cb_parm_s {
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FILE *fp;
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DEK dek;
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int eof_seen;
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int ready;
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int readerror;
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int bufsize;
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unsigned char *buffer;
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int buflen;
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};
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static KsbaCert
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get_default_recipient (void)
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{
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const char key[] =
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"/CN=test cert 1,OU=Aegypten Project,O=g10 Code GmbH,L=Düsseldorf,C=DE";
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KEYDB_SEARCH_DESC desc;
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KsbaCert cert = NULL;
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KEYDB_HANDLE kh = NULL;
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int rc;
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rc = keydb_classify_name (key, &desc);
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if (rc)
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{
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log_error ("failed to find recipient: %s\n", gnupg_strerror (rc));
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return NULL;
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}
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kh = keydb_new (0);
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if (!kh)
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return NULL;
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rc = keydb_search (kh, &desc, 1);
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if (rc)
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{
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log_debug ("failed to find default certificate: rc=%d\n", rc);
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}
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else
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{
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rc = keydb_get_cert (kh, &cert);
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if (rc)
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{
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log_debug ("failed to get cert: rc=%d\n", rc);
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}
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}
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keydb_release (kh);
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return cert;
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}
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/* initialize the data encryptionkey (session key) */
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static int
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init_dek (DEK dek)
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{
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int rc=0, mode, i;
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dek->algo = gcry_cipher_map_name (dek->algoid);
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mode = gcry_cipher_mode_from_oid (dek->algoid);
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if (!dek->algo || !mode)
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{
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log_error ("unsupported algorithm `%s'\n", dek->algoid);
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return GNUPG_Unsupported_Algorithm;
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}
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dek->keylen = gcry_cipher_get_algo_keylen (dek->algo);
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if (!dek->keylen || dek->keylen > sizeof (dek->key))
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return GNUPG_Bug;
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dek->ivlen = gcry_cipher_get_algo_blklen (dek->algo);
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if (!dek->ivlen || dek->ivlen > sizeof (dek->iv))
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return GNUPG_Bug;
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if (dek->keylen < 100/8)
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{ /* make sure we don't use weak keys */
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log_error ("key length of `%s' too small\n", dek->algoid);
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return GNUPG_Unsupported_Algorithm;
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}
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dek->chd = gcry_cipher_open (dek->algo, mode, GCRY_CIPHER_SECURE);
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if (!dek->chd)
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{
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log_error ("failed to create cipher context: %s\n", gcry_strerror (-1));
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return GNUPG_General_Error;
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}
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for (i=0; i < 8; i++)
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{
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gcry_randomize (dek->key, dek->keylen, GCRY_STRONG_RANDOM );
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rc = gcry_cipher_setkey (dek->chd, dek->key, dek->keylen);
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if (rc != GCRYERR_WEAK_KEY)
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break;
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log_info(_("weak key created - retrying\n") );
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}
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if (rc)
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{
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log_error ("failed to set the key: %s\n", gcry_strerror (rc));
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gcry_cipher_close (dek->chd);
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dek->chd = NULL;
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return map_gcry_err (rc);
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}
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gcry_randomize (dek->iv, dek->ivlen, GCRY_STRONG_RANDOM);
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rc = gcry_cipher_setiv (dek->chd, dek->iv, dek->ivlen);
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if (rc)
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{
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log_error ("failed to set the IV: %s\n", gcry_strerror (rc));
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gcry_cipher_close (dek->chd);
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dek->chd = NULL;
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return map_gcry_err (rc);
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}
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return 0;
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}
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/* Encode the session key. NBITS is the number of bits which should be
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used for packing the session key. returns: An mpi with the session
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key (caller must free) */
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static GCRY_MPI
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encode_session_key (DEK dek, unsigned int nbits)
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{
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int nframe = (nbits+7) / 8;
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byte *p;
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byte *frame;
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int i,n;
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MPI a;
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if (dek->keylen + 7 > nframe || !nframe)
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log_bug ("can't encode a %d bit key in a %d bits frame\n",
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dek->keylen*8, nbits );
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/* We encode the session key in this way:
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*
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* 0 2 RND(n bytes) 0 KEY(k bytes)
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*
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* (But how can we store the leading 0 - the external representaion
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* of MPIs doesn't allow leading zeroes =:-)
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*
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* RND are non-zero random bytes.
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* KEY is the encryption key (session key)
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*/
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frame = gcry_xmalloc_secure (nframe);
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n = 0;
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frame[n++] = 0;
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frame[n++] = 2;
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i = nframe - 3 - dek->keylen;
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assert (i > 0);
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p = gcry_random_bytes_secure (i, GCRY_STRONG_RANDOM);
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/* replace zero bytes by new values */
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for (;;)
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{
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int j, k;
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byte *pp;
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/* count the zero bytes */
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for(j=k=0; j < i; j++ )
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{
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if( !p[j] )
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k++;
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}
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if( !k )
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break; /* okay: no zero bytes */
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k += k/128; /* better get some more */
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pp = gcry_random_bytes_secure (k, GCRY_STRONG_RANDOM);
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for (j=0; j < i && k; j++)
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{
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if( !p[j] )
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p[j] = pp[--k];
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}
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xfree (pp);
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}
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memcpy (frame+n, p, i);
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xfree (p);
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n += i;
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frame[n++] = 0;
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memcpy (frame+n, dek->key, dek->keylen);
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n += dek->keylen;
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assert (n == nframe);
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if (gcry_mpi_scan (&a, GCRYMPI_FMT_USG, frame, &nframe) )
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BUG ();
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gcry_free(frame);
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return a;
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}
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/* encrypt the DEK under the key contained in CERT and return it as a
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canonical S-Exp in encval */
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static int
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encrypt_dek (const DEK dek, KsbaCert cert, char **encval)
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{
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GCRY_SEXP s_ciph, s_data, s_pkey;
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int rc;
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char *buf;
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size_t len;
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*encval = NULL;
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/* get the key from the cert */
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buf = ksba_cert_get_public_key (cert);
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if (!buf)
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{
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log_error ("no public key for recipient\n");
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return GNUPG_No_Public_Key;
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}
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rc = gcry_sexp_sscan (&s_pkey, NULL, buf, strlen(buf));
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xfree (buf); buf = NULL;
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if (rc)
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{
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log_error ("gcry_sexp_scan failed: %s\n", gcry_strerror (rc));
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return map_gcry_err (rc);
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}
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/* put the encoded cleartext into a simple list */
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{
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/* fixme: actually the pkcs-1 encoding should go into libgcrypt */
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GCRY_MPI data = encode_session_key (dek, gcry_pk_get_nbits (s_pkey));
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if (!data)
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{
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gcry_mpi_release (data);
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return GNUPG_General_Error;
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}
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if (gcry_sexp_build (&s_data, NULL, "%m", data))
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BUG ();
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gcry_mpi_release (data);
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}
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/* pass it to libgcrypt */
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rc = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
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gcry_sexp_release (s_data);
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gcry_sexp_release (s_pkey);
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/* reformat it */
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len = gcry_sexp_sprint (s_ciph, GCRYSEXP_FMT_CANON, NULL, 0);
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assert (len);
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buf = xtrymalloc (len);
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if (!buf)
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{
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gcry_sexp_release (s_ciph);
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return GNUPG_Out_Of_Core;
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}
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len = gcry_sexp_sprint (s_ciph, GCRYSEXP_FMT_CANON, buf, len);
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assert (len);
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*encval = buf;
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return 0;
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}
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/* do the actual encryption */
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static int
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encrypt_cb (void *cb_value, char *buffer, size_t count, size_t *nread)
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{
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struct encrypt_cb_parm_s *parm = cb_value;
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int blklen = parm->dek->ivlen;
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unsigned char *p;
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size_t n;
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*nread = 0;
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if (!buffer)
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return -1; /* not supported */
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if (parm->ready)
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return -1;
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if (count < blklen)
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BUG ();
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if (!parm->eof_seen)
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{ /* fillup the buffer */
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p = parm->buffer;
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for (n=parm->buflen; n < parm->bufsize; n++)
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{
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int c = getc (parm->fp);
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if (c == EOF)
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{
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if (ferror (parm->fp))
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{
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parm->readerror = errno;
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return -1;
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}
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parm->eof_seen = 1;
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break;
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}
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p[n] = c;
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}
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parm->buflen = n;
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}
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n = parm->buflen < count? parm->buflen : count;
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n = n/blklen * blklen;
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if (n)
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{ /* encrypt the stuff */
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gcry_cipher_encrypt (parm->dek->chd, buffer, n, parm->buffer, n);
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*nread = n;
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/* Who cares about cycles, take the easy way and shift the buffer */
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parm->buflen -= n;
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memmove (parm->buffer, parm->buffer+n, parm->buflen);
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}
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else if (parm->eof_seen)
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{ /* no complete block but eof: add padding */
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/* fixme: we should try to do this also in the above code path */
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int i, npad = blklen - (parm->buflen % blklen);
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p = parm->buffer;
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for (n=parm->buflen, i=0; n < parm->bufsize && i < npad; n++, i++)
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p[n] = npad;
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gcry_cipher_encrypt (parm->dek->chd, buffer, n, parm->buffer, n);
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*nread = n;
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parm->ready = 1;
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}
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return 0;
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}
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/* Perform an encrypt operation.
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Encrypt the data received on DATA-FD and write it to OUT_FP. The
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recipients are take from the certificate given in recplist; if this
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is NULL it will be encrypted for a default recipient */
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int
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gpgsm_encrypt (CTRL ctrl, CERTLIST recplist, int data_fd, FILE *out_fp)
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{
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int rc = 0;
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Base64Context b64writer = NULL;
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KsbaError err;
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KsbaWriter writer;
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KsbaReader reader = NULL;
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KsbaCMS cms = NULL;
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KsbaStopReason stopreason;
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KEYDB_HANDLE kh = NULL;
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struct encrypt_cb_parm_s encparm;
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DEK dek = NULL;
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int recpno;
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FILE *data_fp = NULL;
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struct certlist_s help_recplist;
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CERTLIST cl;
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memset (&encparm, 0, sizeof encparm);
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help_recplist.next = NULL;
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help_recplist.cert = NULL;
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kh = keydb_new (0);
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if (!kh)
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{
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log_error (_("failed to allocated keyDB handle\n"));
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rc = GNUPG_General_Error;
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goto leave;
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}
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/* If no recipient list is given, use a default one */
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if (!recplist)
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{
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help_recplist.cert = get_default_recipient ();
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if (!help_recplist.cert)
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{
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log_error ("no default recipient found\n");
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rc = seterr (General_Error);
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goto leave;
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}
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recplist = &help_recplist;
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}
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data_fp = fdopen ( dup (data_fd), "rb");
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if (!data_fp)
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{
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log_error ("fdopen() failed: %s\n", strerror (errno));
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rc = seterr (IO_Error);
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goto leave;
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}
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reader = ksba_reader_new ();
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if (!reader)
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rc = KSBA_Out_Of_Core;
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if (!rc)
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rc = ksba_reader_set_cb (reader, encrypt_cb, &encparm);
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if (rc)
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{
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rc = map_ksba_err (rc);
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goto leave;
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}
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encparm.fp = data_fp;
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rc = gpgsm_create_writer (&b64writer, ctrl, out_fp, &writer);
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if (rc)
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{
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log_error ("can't create writer: %s\n", gnupg_strerror (rc));
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goto leave;
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}
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cms = ksba_cms_new ();
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if (!cms)
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{
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rc = seterr (Out_Of_Core);
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goto leave;
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}
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err = ksba_cms_set_reader_writer (cms, reader, writer);
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if (err)
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{
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log_debug ("ksba_cms_set_reader_writer failed: %s\n",
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ksba_strerror (err));
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rc = map_ksba_err (err);
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goto leave;
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}
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/* We are going to create enveloped data with uninterpreted data as
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inner content */
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err = ksba_cms_set_content_type (cms, 0, KSBA_CT_ENVELOPED_DATA);
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if (!err)
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err = ksba_cms_set_content_type (cms, 1, KSBA_CT_DATA);
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if (err)
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{
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log_debug ("ksba_cms_set_content_type failed: %s\n",
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ksba_strerror (err));
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rc = map_ksba_err (err);
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goto leave;
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}
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/* create a session key */
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dek = xtrycalloc (1, sizeof *dek); /* hmmm: should we put it into secmem?*/
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if (!dek)
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rc = GNUPG_Out_Of_Core;
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else
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{
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dek->algoid = opt.def_cipher_algoid;
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rc = init_dek (dek);
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}
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if (rc)
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{
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log_error ("failed to create the session key: %s\n",
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gnupg_strerror (rc));
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goto leave;
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}
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err = ksba_cms_set_content_enc_algo (cms, dek->algoid, dek->iv, dek->ivlen);
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if (err)
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{
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log_error ("ksba_cms_set_content_enc_algo failed: %s\n",
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ksba_strerror (err));
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rc = map_ksba_err (err);
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goto leave;
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}
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encparm.dek = dek;
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/* fixme: we should use a larger buffer - the small one is better
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for testing */
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encparm.bufsize = 10 * dek->ivlen;
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encparm.buffer = xtrymalloc (encparm.bufsize);
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if (!encparm.buffer)
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{
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rc = seterr (Out_Of_Core);
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goto leave;
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}
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/* gather certificates of recipients, encrypt the session key for
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each and store them in the CMS object */
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for (recpno = 0, cl = recplist; cl; recpno++, cl = cl->next)
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{
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char *encval;
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rc = encrypt_dek (dek, cl->cert, &encval);
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if (rc)
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{
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log_error ("encryption failed for recipient no. %d: %s\n",
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recpno, gnupg_strerror (rc));
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goto leave;
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}
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err = ksba_cms_add_recipient (cms, cl->cert);
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if (err)
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{
|
||
log_error ("ksba_cms_add_recipient failed: %s\n",
|
||
ksba_strerror (err));
|
||
rc = map_ksba_err (err);
|
||
xfree (encval);
|
||
goto leave;
|
||
}
|
||
|
||
err = ksba_cms_set_enc_val (cms, recpno, encval);
|
||
xfree (encval);
|
||
if (err)
|
||
{
|
||
log_error ("ksba_cms_set_enc_val failed: %s\n",
|
||
ksba_strerror (err));
|
||
rc = map_ksba_err (err);
|
||
goto leave;
|
||
}
|
||
}
|
||
|
||
/* main control loop for encryption */
|
||
recpno = 0;
|
||
do
|
||
{
|
||
err = ksba_cms_build (cms, &stopreason);
|
||
if (err)
|
||
{
|
||
log_debug ("ksba_cms_build failed: %s\n", ksba_strerror (err));
|
||
rc = map_ksba_err (err);
|
||
goto leave;
|
||
}
|
||
}
|
||
while (stopreason != KSBA_SR_READY);
|
||
|
||
if (encparm.readerror)
|
||
{
|
||
log_error ("error reading input: %s\n", strerror (encparm.readerror));
|
||
rc = seterr (Read_Error);
|
||
goto leave;
|
||
}
|
||
|
||
|
||
rc = gpgsm_finish_writer (b64writer);
|
||
if (rc)
|
||
{
|
||
log_error ("write failed: %s\n", gnupg_strerror (rc));
|
||
goto leave;
|
||
}
|
||
log_info ("encrypted data created\n");
|
||
|
||
leave:
|
||
ksba_cms_release (cms);
|
||
gpgsm_destroy_writer (b64writer);
|
||
ksba_reader_release (reader);
|
||
keydb_release (kh);
|
||
xfree (dek);
|
||
if (data_fp)
|
||
fclose (data_fp);
|
||
xfree (encparm.buffer);
|
||
if (help_recplist.cert)
|
||
ksba_cert_release (help_recplist.cert);
|
||
return rc;
|
||
}
|