/* pubkey-enc.c - public key encoded packet handling * Copyright (C) 1998, 1999, 2000, 2001, 2002 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 2 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, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include #include #include #include #include #include "util.h" #include "memory.h" #include "packet.h" #include "mpi.h" #include "keydb.h" #include "trustdb.h" #include "cipher.h" #include "status.h" #include "options.h" #include "main.h" #include "i18n.h" static int get_it( PKT_pubkey_enc *k, DEK *dek, PKT_secret_key *sk, u32 *keyid ); /* check that the given algo is mentioned in one of the valid user IDs */ static int is_algo_in_prefs ( KBNODE keyblock, preftype_t type, int algo ) { KBNODE k; for (k=keyblock; k; k=k->next) { if (k->pkt->pkttype == PKT_USER_ID) { PKT_user_id *uid = k->pkt->pkt.user_id; prefitem_t *prefs = uid->prefs; if (uid->created && !uid->is_revoked && prefs ) { for (; prefs->type; prefs++ ) if (prefs->type == type && prefs->value == algo) return 1; } } } return 0; } /**************** * Get the session key from a pubkey enc paket and return * it in DEK, which should have been allocated in secure memory. */ int get_session_key( PKT_pubkey_enc *k, DEK *dek ) { PKT_secret_key *sk = NULL; int rc; rc = check_pubkey_algo2 (k->pubkey_algo, PUBKEY_USAGE_ENC); if( rc ) goto leave; if( (k->keyid[0] || k->keyid[1]) && !opt.try_all_secrets ) { sk = m_alloc_clear( sizeof *sk ); sk->pubkey_algo = k->pubkey_algo; /* we want a pubkey with this algo*/ if( !(rc = get_seckey( sk, k->keyid )) ) rc = get_it( k, dek, sk, k->keyid ); } else { /* anonymous receiver: Try all available secret keys */ void *enum_context = NULL; u32 keyid[2]; for(;;) { if( sk ) free_secret_key( sk ); sk = m_alloc_clear( sizeof *sk ); rc=enum_secret_keys( &enum_context, sk, 1); if( rc ) { rc = G10ERR_NO_SECKEY; break; } if( sk->pubkey_algo != k->pubkey_algo ) continue; keyid_from_sk( sk, keyid ); log_info(_("anonymous recipient; trying secret key %08lX ...\n"), (ulong)keyid[1] ); rc = check_secret_key( sk, 1 ); /* ask only once */ if( !rc ) rc = get_it( k, dek, sk, keyid ); if( !rc ) { log_info(_("okay, we are the anonymous recipient.\n") ); break; } } enum_secret_keys( &enum_context, NULL, 0 ); /* free context */ } leave: if( sk ) free_secret_key( sk ); return rc; } static int get_it( PKT_pubkey_enc *enc, DEK *dek, PKT_secret_key *sk, u32 *keyid ) { int rc; MPI plain_dek = NULL; byte *frame = NULL; unsigned n, nframe; u16 csum, csum2; rc = pubkey_decrypt(sk->pubkey_algo, &plain_dek, enc->data, sk->skey ); if( rc ) goto leave; frame = mpi_get_buffer( plain_dek, &nframe, NULL ); mpi_free( plain_dek ); plain_dek = NULL; /* Now get the DEK (data encryption key) from the frame * * Old versions encode the DEK in in this format (msb is left): * * 0 1 DEK(16 bytes) CSUM(2 bytes) 0 RND(n bytes) 2 * * Later versions encode the DEK like this: * * 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes) * * (mpi_get_buffer already removed the leading zero). * * RND are non-zero randow bytes. * A is the cipher algorithm * DEK is the encryption key (session key) with length k * CSUM */ if( DBG_CIPHER ) log_hexdump("DEK frame:", frame, nframe ); n=0; if( n + 7 > nframe ) { rc = G10ERR_WRONG_SECKEY; goto leave; } if( frame[n] == 1 && frame[nframe-1] == 2 ) { log_info(_("old encoding of the DEK is not supported\n")); rc = G10ERR_CIPHER_ALGO; goto leave; } if( frame[n] != 2 ) /* somethink is wrong */ { rc = G10ERR_WRONG_SECKEY; goto leave; } for(n++; n < nframe && frame[n]; n++ ) /* skip the random bytes */ ; n++; /* and the zero byte */ if( n + 4 > nframe ) { rc = G10ERR_WRONG_SECKEY; goto leave; } dek->keylen = nframe - (n+1) - 2; dek->algo = frame[n++]; if( dek->algo == CIPHER_ALGO_IDEA ) write_status(STATUS_RSA_OR_IDEA); rc = check_cipher_algo( dek->algo ); if( rc ) { if( !opt.quiet && rc == G10ERR_CIPHER_ALGO ) { log_info(_("cipher algorithm %d%s is unknown or disabled\n"), dek->algo, dek->algo == CIPHER_ALGO_IDEA? " (IDEA)":""); if(dek->algo==CIPHER_ALGO_IDEA) idea_cipher_warn(0); } dek->algo = 0; goto leave; } if( (dek->keylen*8) != cipher_get_keylen( dek->algo ) ) { rc = G10ERR_WRONG_SECKEY; goto leave; } /* copy the key to DEK and compare the checksum */ csum = frame[nframe-2] << 8; csum |= frame[nframe-1]; memcpy( dek->key, frame+n, dek->keylen ); for( csum2=0, n=0; n < dek->keylen; n++ ) csum2 += dek->key[n]; if( csum != csum2 ) { rc = G10ERR_WRONG_SECKEY; goto leave; } if( DBG_CIPHER ) log_hexdump("DEK is:", dek->key, dek->keylen ); /* check that the algo is in the preferences and whether it has expired */ { PKT_public_key *pk = NULL; KBNODE pkb = get_pubkeyblock (keyid); if( !pkb ) { rc = -1; log_error("oops: public key not found for preference check\n"); } else if( pkb->pkt->pkt.public_key->selfsigversion > 3 && dek->algo != CIPHER_ALGO_3DES && !is_algo_in_prefs( pkb, PREFTYPE_SYM, dek->algo ) ) { /* Don't print a note while we are not on verbose mode, * the cipher is blowfish and the preferences have twofish * listed */ if( opt.verbose || dek->algo != CIPHER_ALGO_BLOWFISH || !is_algo_in_prefs( pkb, PREFTYPE_SYM, CIPHER_ALGO_TWOFISH)) log_info(_( "NOTE: cipher algorithm %d not found in preferences\n"), dek->algo ); } if (!rc) { KBNODE k; for (k=pkb; k; k = k->next) { if (k->pkt->pkttype == PKT_PUBLIC_KEY || k->pkt->pkttype == PKT_PUBLIC_SUBKEY){ u32 aki[2]; keyid_from_pk(k->pkt->pkt.public_key, aki); if (aki[0]==keyid[0] && aki[1]==keyid[1]) { pk = k->pkt->pkt.public_key; break; } } } if (!pk) BUG (); if ( pk->expiredate && pk->expiredate <= make_timestamp() ) { log_info(_("NOTE: secret key %08lX expired at %s\n"), (ulong)keyid[1], asctimestamp( pk->expiredate) ); } } if ( pk->is_revoked ) { log_info( _("NOTE: key has been revoked") ); putc( '\n', log_stream() ); show_revocation_reason( pk, 1 ); } release_kbnode (pkb); rc = 0; } leave: mpi_free(plain_dek); m_free(frame); return rc; } /**************** * Get the session key from the given string. * String is supposed to be formatted as this: * : */ int get_override_session_key( DEK *dek, const char *string ) { const char *s; int i; if ( !string ) return G10ERR_BAD_KEY; dek->algo = atoi(string); if ( dek->algo < 1 ) return G10ERR_BAD_KEY; if ( !(s = strchr ( string, ':' )) ) return G10ERR_BAD_KEY; s++; for(i=0; i < DIM(dek->key) && *s; i++, s +=2 ) { int c = hextobyte ( s ); if (c == -1) return G10ERR_BAD_KEY; dek->key[i] = c; } if ( *s ) return G10ERR_BAD_KEY; dek->keylen = i; return 0; }