--- /dev/null
+/*
+ * sigcheck.c - routines to check OpenPGP signatures
+ *
+ * Copyright 2012 Jonathan McDowell <noodles@earth.li>
+ *
+ * This program 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; version 2 of the License.
+ *
+ * This program 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., 51
+ * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <stdint.h>
+
+#include "config.h"
+#include "keystructs.h"
+#include "log.h"
+#include "openpgp.h"
+#include "sigcheck.h"
+
+#ifdef HAVE_NETTLE
+#include <nettle/md5.h>
+#include <nettle/sha.h>
+#else
+#include "md5.h"
+#include "sha1.h"
+#endif
+
+int check_packet_sighash(struct openpgp_publickey *key,
+ struct openpgp_packet *packet,
+ struct openpgp_packet *sig)
+{
+ uint8_t hashtype;
+ uint8_t *sighash;
+ size_t siglen, unhashedlen;
+ struct sha1_ctx sha1_context;
+ struct md5_ctx md5_context;
+#ifdef NETTLE_WITH_SHA224
+ struct sha224_ctx sha224_context;
+#endif
+#ifdef NETTLE_WITH_SHA256
+ struct sha256_ctx sha256_context;
+#endif
+#ifdef NETTLE_WITH_SHA384
+ struct sha384_ctx sha384_context;
+#endif
+#ifdef NETTLE_WITH_SHA512
+ struct sha512_ctx sha512_context;
+#endif
+ uint8_t keyheader[3];
+ uint8_t packetheader[5];
+ uint8_t v4trailer[6];
+ uint8_t hash[20];
+ uint8_t *hashdata[8];
+ size_t hashlen[8];
+ int chunks, i;
+
+ keyheader[0] = 0x99;
+ keyheader[1] = key->publickey->length >> 8;
+ keyheader[2] = key->publickey->length & 0xFF;
+ hashdata[0] = keyheader;
+ hashlen[0] = 3;
+ hashdata[1] = key->publickey->data;
+ hashlen[1] = key->publickey->length;
+ chunks = 2;
+
+ switch (sig->data[0]) {
+ case 2:
+ case 3:
+ hashtype = sig->data[16];
+
+ if (packet != NULL) {
+ if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
+ packetheader[0] = 0x99;
+ packetheader[1] = packet->length >> 8;
+ packetheader[2] = packet->length & 0xFF;
+ hashdata[chunks] = packetheader;
+ hashlen[chunks] = 3;
+ chunks++;
+ }
+
+ // TODO: Things other than UIDS/subkeys?
+ hashdata[chunks] = packet->data;
+ hashlen[chunks] = packet->length;
+ chunks++;
+ }
+
+ hashdata[chunks] = &sig->data[2];
+ hashlen[chunks] = 5;
+ chunks++;
+ sighash = &sig->data[17];
+ break;
+ case 4:
+ hashtype = sig->data[3];
+
+ if (packet != NULL) {
+ if (packet->tag == OPENPGP_PACKET_PUBLICSUBKEY) {
+ packetheader[0] = 0x99;
+ packetheader[1] = packet->length >> 8;
+ packetheader[2] = packet->length & 0xFF;
+ hashdata[chunks] = packetheader;
+ hashlen[chunks] = 3;
+ chunks++;
+ } else if (packet->tag == OPENPGP_PACKET_UID ||
+ packet->tag == OPENPGP_PACKET_UAT) {
+ packetheader[0] = (packet->tag ==
+ OPENPGP_PACKET_UID) ? 0xB4 : 0xD1;
+ packetheader[1] = packet->length >> 24;
+ packetheader[2] = (packet->length >> 16) & 0xFF;
+ packetheader[3] = (packet->length >> 8) & 0xFF;
+ packetheader[4] = packet->length & 0xFF;
+ hashdata[chunks] = packetheader;
+ hashlen[chunks] = 5;
+ chunks++;
+ }
+ hashdata[chunks] = packet->data;
+ hashlen[chunks] = packet->length;
+ chunks++;
+ }
+
+ hashdata[chunks] = sig->data;
+ hashlen[chunks] = siglen = (sig->data[4] << 8) +
+ sig->data[5] + 6;;
+ chunks++;
+
+ v4trailer[0] = 4;
+ v4trailer[1] = 0xFF;
+ v4trailer[2] = siglen >> 24;
+ v4trailer[3] = (siglen >> 16) & 0xFF;
+ v4trailer[4] = (siglen >> 8) & 0xFF;
+ v4trailer[5] = siglen & 0xFF;
+ hashdata[chunks] = v4trailer;
+ hashlen[chunks] = 6;
+ chunks++;
+
+ unhashedlen = (sig->data[siglen] << 8) +
+ sig->data[siglen + 1];
+ sighash = &sig->data[siglen + unhashedlen + 2];
+ break;
+ default:
+ logthing(LOGTHING_ERROR, "Unknown signature version %d",
+ sig->data[0]);
+ return -1;
+ }
+
+ switch (hashtype) {
+ case OPENPGP_HASH_MD5:
+ md5_init(&md5_context);
+ for (i = 0; i < chunks; i++) {
+ md5_update(&md5_context, hashlen[i], hashdata[i]);
+ }
+ md5_digest(&md5_context, 16, hash);
+ break;
+ case OPENPGP_HASH_SHA1:
+ sha1_init(&sha1_context);
+ for (i = 0; i < chunks; i++) {
+ sha1_update(&sha1_context, hashlen[i], hashdata[i]);
+ }
+ sha1_digest(&sha1_context, 20, hash);
+ break;
+ case OPENPGP_HASH_SHA224:
+#ifdef NETTLE_WITH_SHA224
+ sha224_init(&sha224_context);
+ for (i = 0; i < chunks; i++) {
+ sha224_update(&sha224_context, hashlen[i],
+ hashdata[i]);
+ }
+ sha224_digest(&sha224_context, SHA224_DIGEST_SIZE, hash);
+#else
+ logthing(LOGTHING_INFO, "SHA224 support not available.");
+#endif
+ break;
+ case OPENPGP_HASH_SHA256:
+#ifdef NETTLE_WITH_SHA256
+ sha256_init(&sha256_context);
+ for (i = 0; i < chunks; i++) {
+ sha256_update(&sha256_context, hashlen[i],
+ hashdata[i]);
+ }
+ sha256_digest(&sha256_context, SHA256_DIGEST_SIZE, hash);
+#else
+ logthing(LOGTHING_INFO, "SHA256 support not available.");
+#endif
+ break;
+ case OPENPGP_HASH_SHA384:
+#ifdef NETTLE_WITH_SHA384
+ sha384_init(&sha384_context);
+ for (i = 0; i < chunks; i++) {
+ sha384_update(&sha384_context, hashlen[i],
+ hashdata[i]);
+ }
+ sha384_digest(&sha384_context, SHA384_DIGEST_SIZE, hash);
+#else
+ logthing(LOGTHING_INFO, "SHA384 support not available.");
+#endif
+ break;
+ case OPENPGP_HASH_SHA512:
+#ifdef NETTLE_WITH_SHA512
+ sha512_init(&sha512_context);
+ for (i = 0; i < chunks; i++) {
+ sha512_update(&sha512_context, hashlen[i],
+ hashdata[i]);
+ }
+ sha512_digest(&sha512_context, SHA512_DIGEST_SIZE, hash);
+#else
+ logthing(LOGTHING_INFO, "SHA512 support not available.");
+#endif
+ break;
+ default:
+ logthing(LOGTHING_ERROR, "Unsupported signature hash type %d",
+ hashtype);
+ return -1;
+ }
+
+ logthing(LOGTHING_DEBUG, "Hash type: %d, %d chunks, "
+ "calculated: %02X%02X / actual: %02X%02X\n",
+ hashtype, chunks,
+ hash[0], hash[1], sighash[0], sighash[1]);
+
+ return (hash[0] == sighash[0] && hash[1] == sighash[1]);
+}
projects / onak.git / blobdiff