398 lines
10 KiB
C
398 lines
10 KiB
C
int dh_encrypt_key(const unsigned char *inkey, unsigned long keylen,
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unsigned char *out, unsigned long *len,
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prng_state *prng, int wprng, int hash,
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dh_key *key)
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{
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unsigned char pub_expt[1536], dh_shared[1536], skey[MAXBLOCKSIZE];
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dh_key pubkey;
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unsigned long x, y, z, hashsize, pubkeysize;
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int errno;
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_ARGCHK(inkey != NULL);
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_ARGCHK(out != NULL);
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_ARGCHK(len != NULL);
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_ARGCHK(key != NULL);
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/* check that wprng/hash are not invalid */
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if ((errno = prng_is_valid(wprng)) != CRYPT_OK) {
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return errno;
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}
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if ((errno = hash_is_valid(hash)) != CRYPT_OK) {
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return errno;
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}
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if (keylen > hash_descriptor[hash].hashsize) {
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return CRYPT_INVALID_ARG;
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}
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/* make a random key and export the public copy */
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if ((errno = dh_make_key(prng, wprng, dh_get_size(key), &pubkey)) != CRYPT_OK) {
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return errno;
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}
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pubkeysize = sizeof(pub_expt);
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if ((errno = dh_export(pub_expt, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
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dh_free(&pubkey);
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return errno;
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}
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/* now check if the out buffer is big enough */
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if (*len < (9 + PACKET_SIZE + pubkeysize + keylen)) {
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dh_free(&pubkey);
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return CRYPT_BUFFER_OVERFLOW;
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}
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/* make random key */
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hashsize = hash_descriptor[hash].hashsize;
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x = sizeof(dh_shared);
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if ((errno = dh_shared_secret(&pubkey, key, dh_shared, &x)) != CRYPT_OK) {
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dh_free(&pubkey);
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return errno;
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}
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dh_free(&pubkey);
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z = sizeof(skey);
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if ((errno = hash_memory(hash, dh_shared, x, skey, &z)) != CRYPT_OK) {
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return errno;
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}
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/* output header */
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y = PACKET_SIZE;
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/* size of hash name and the name itself */
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out[y++] = hash_descriptor[hash].ID;
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/* length of DH pubkey and the key itself */
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STORE32L(pubkeysize, out+y);
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y += 4;
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for (x = 0; x < pubkeysize; x++, y++) {
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out[y] = pub_expt[x];
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}
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/* Store the encrypted key */
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STORE32L(keylen, out+y);
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y += 4;
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for (x = 0; x < keylen; x++, y++) {
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out[y] = skey[x] ^ inkey[x];
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}
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/* store header */
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packet_store_header(out, PACKET_SECT_DH, PACKET_SUB_ENC_KEY);
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#ifdef CLEAN_STACK
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/* clean up */
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zeromem(pub_expt, sizeof(pub_expt));
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zeromem(dh_shared, sizeof(dh_shared));
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zeromem(skey, sizeof(skey));
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#endif
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*len = y;
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return CRYPT_OK;
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}
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int dh_decrypt_key(const unsigned char *in, unsigned long inlen,
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unsigned char *outkey, unsigned long *keylen,
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dh_key *key)
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{
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unsigned char shared_secret[1536], skey[MAXBLOCKSIZE];
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unsigned long x, y, z, res, hashsize, keysize;
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int hash, errno;
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dh_key pubkey;
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_ARGCHK(in != NULL);
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_ARGCHK(outkey != NULL);
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_ARGCHK(keylen != NULL);
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_ARGCHK(key != NULL);
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/* right key type? */
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if (key->type != PK_PRIVATE) {
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return CRYPT_PK_NOT_PRIVATE;
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}
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/* check if initial header should fit */
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if (inlen < PACKET_SIZE+1+4+4) {
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return CRYPT_INVALID_PACKET;
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} else {
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inlen -= PACKET_SIZE+1+4+4;
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}
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/* is header correct? */
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if ((errno = packet_valid_header((unsigned char *)in, PACKET_SECT_DH, PACKET_SUB_ENC_KEY)) != CRYPT_OK) {
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return errno;
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}
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/* now lets get the hash name */
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y = PACKET_SIZE;
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hash = find_hash_id(in[y++]);
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if (hash == -1) {
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return CRYPT_INVALID_HASH;
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}
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/* common values */
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hashsize = hash_descriptor[hash].hashsize;
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/* get public key */
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LOAD32L(x, in+y);
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/* now check if the imported key will fit */
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if (inlen < x) {
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return CRYPT_INVALID_PACKET;
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} else {
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inlen -= x;
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}
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y += 4;
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if ((errno = dh_import(in+y, x, &pubkey)) != CRYPT_OK) {
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return errno;
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}
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y += x;
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/* make shared key */
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x = sizeof(shared_secret);
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if ((errno = dh_shared_secret(key, &pubkey, shared_secret, &x)) != CRYPT_OK) {
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dh_free(&pubkey);
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return errno;
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}
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dh_free(&pubkey);
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z = sizeof(skey);
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if ((errno = hash_memory(hash, shared_secret, x, skey, &z)) != CRYPT_OK) {
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return errno;
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}
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/* load in the encrypted key */
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LOAD32L(keysize, in+y);
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/* will the outkey fit as part of the input */
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if (inlen < keysize) {
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return CRYPT_INVALID_PACKET;
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} else {
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inlen -= keysize;
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}
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if (keysize > *keylen) {
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res = CRYPT_BUFFER_OVERFLOW;
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goto done;
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}
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y += 4;
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*keylen = keysize;
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for (x = 0; x < keysize; x++, y++) {
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outkey[x] = skey[x] ^ in[y];
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}
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res = CRYPT_OK;
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done:
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#ifdef CLEAN_STACK
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zeromem(shared_secret, sizeof(shared_secret));
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zeromem(skey, sizeof(skey));
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#endif
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return res;
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}
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int dh_sign_hash(const unsigned char *in, unsigned long inlen,
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unsigned char *out, unsigned long *outlen,
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prng_state *prng, int wprng, dh_key *key)
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{
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mp_int a, b, k, m, g, p, p1, tmp;
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unsigned char buf[1536], md[MAXBLOCKSIZE];
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unsigned long x, y;
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int res, errno;
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_ARGCHK(in != NULL);
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_ARGCHK(out != NULL);
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_ARGCHK(outlen != NULL);
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_ARGCHK(key != NULL);
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/* check parameters */
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if (key->type != PK_PRIVATE) {
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return CRYPT_PK_NOT_PRIVATE;
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}
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if ((errno = prng_is_valid(wprng)) != CRYPT_OK) {
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return errno;
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}
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/* is the IDX valid ? */
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if (!is_valid_idx(key->idx)) {
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return CRYPT_PK_INVALID_TYPE;
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}
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/* hash the message */
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md[0] = 0;
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memcpy(md+1, in, MIN(sizeof(md) - 1, inlen));
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/* make up a random value k,
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* since the order of the group is prime
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* we need not check if gcd(k, r) is 1
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*/
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buf[0] = 0;
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if (prng_descriptor[wprng].read(buf+1, sets[key->idx].size-1, prng) !=
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(unsigned long)(sets[key->idx].size-1)) {
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return CRYPT_ERROR_READPRNG;
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}
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/* init bignums */
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if (mp_init_multi(&a, &b, &k, &m, &p, &g, &p1, &tmp, NULL) != MP_OKAY) {
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return CRYPT_MEM;
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}
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/* load k and m */
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if (mp_read_raw(&m, md, 1+MIN(sizeof(md) - 1, inlen)) != MP_OKAY) { goto error; }
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if (mp_read_raw(&k, buf, sets[key->idx].size) != MP_OKAY) { goto error; }
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/* load g, p and p1 */
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if (mp_read_radix(&g, sets[key->idx].base, 64) != MP_OKAY) { goto error; }
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if (mp_read_radix(&p, sets[key->idx].prime, 64) != MP_OKAY) { goto error; }
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if (mp_sub_d(&p, 1, &p1) != MP_OKAY) { goto error; }
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if (mp_div_2(&p1, &p1) != MP_OKAY) { goto error; } /* p1 = (p-1)/2 */
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/* now get a = g^k mod p */
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if (mp_exptmod(&g, &k, &p, &a) != MP_OKAY) { goto error; }
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/* now find M = xa + kb mod p1 or just b = (M - xa)/k mod p1 */
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if (mp_invmod(&k, &p1, &k) != MP_OKAY) { goto error; } /* k = 1/k mod p1 */
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if (mp_mulmod(&a, &key->x, &p1, &tmp) != MP_OKAY) { goto error; } /* tmp = xa */
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if (mp_submod(&m, &tmp, &p1, &tmp) != MP_OKAY) { goto error; } /* tmp = M - xa */
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if (mp_mulmod(&k, &tmp, &p1, &b) != MP_OKAY) { goto error; } /* b = (M - xa)/k */
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/* store header */
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y = PACKET_SIZE;
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/* now store them both (a,b) */
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x = mp_raw_size(&a);
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STORE32L(x, buf+y); y += 4;
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mp_toraw(&a, buf+y); y += x;
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x = mp_raw_size(&b);
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STORE32L(x, buf+y); y += 4;
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mp_toraw(&b, buf+y); y += x;
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/* check if size too big */
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if (*outlen < y) {
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res = CRYPT_BUFFER_OVERFLOW;
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goto done;
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}
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/* store header */
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packet_store_header(buf, PACKET_SECT_DH, PACKET_SUB_SIGNED);
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/* store it */
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memcpy(out, buf, y);
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*outlen = y;
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#ifdef CLEAN_STACK
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zeromem(md, sizeof(md));
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zeromem(buf, sizeof(buf));
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#endif
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res = CRYPT_OK;
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goto done;
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error:
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res = CRYPT_MEM;
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done:
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mp_clear_multi(&tmp, &p1, &g, &p, &m, &k, &b, &a, NULL);
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return res;
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}
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int dh_verify_hash(const unsigned char *sig, unsigned long siglen,
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const unsigned char *hash, unsigned long hashlen,
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int *stat, dh_key *key)
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{
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mp_int a, b, p, g, m, tmp;
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unsigned char md[MAXBLOCKSIZE];
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unsigned long x, y;
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int res, errno;
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_ARGCHK(sig != NULL);
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_ARGCHK(hash != NULL);
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_ARGCHK(stat != NULL);
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_ARGCHK(key != NULL);
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/* default to invalid */
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*stat = 0;
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/* check initial input length */
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if (siglen < PACKET_SIZE+4+4) {
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return CRYPT_INVALID_PACKET;
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} else {
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siglen -= PACKET_SIZE + 4 + 4;
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}
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/* header ok? */
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if ((errno = packet_valid_header((unsigned char *)sig, PACKET_SECT_DH, PACKET_SUB_SIGNED)) != CRYPT_OK) {
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return errno;
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}
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/* get hash out of packet */
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y = PACKET_SIZE;
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/* hash the message */
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md[0] = 0;
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memcpy(md+1, hash, MIN(sizeof(md) - 1, hashlen));
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/* init all bignums */
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if (mp_init_multi(&a, &p, &b, &g, &m, &tmp, NULL) != MP_OKAY) {
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return CRYPT_MEM;
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}
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/* load a and b */
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LOAD32L(x, sig+y);
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if (siglen < x) {
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return CRYPT_INVALID_PACKET;
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} else {
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siglen -= x;
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}
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y += 4;
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if (mp_read_raw(&a, (unsigned char *)sig+y, x) != MP_OKAY) { goto error; }
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y += x;
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LOAD32L(x, sig+y);
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if (siglen < x) {
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return CRYPT_INVALID_PACKET;
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} else {
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siglen -= x;
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}
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y += 4;
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if (mp_read_raw(&b, (unsigned char *)sig+y, x) != MP_OKAY) { goto error; }
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y += x;
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/* load p and g */
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if (mp_read_radix(&p, sets[key->idx].prime, 64) != MP_OKAY) { goto error; }
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if (mp_read_radix(&g, sets[key->idx].base, 64) != MP_OKAY) { goto error; }
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/* load m */
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if (mp_read_raw(&m, md, 1+MIN(sizeof(md)-1, hashlen)) != MP_OKAY) { goto error; }
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/* find g^m mod p */
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if (mp_exptmod(&g, &m, &p, &m) != MP_OKAY) { goto error; } /* m = g^m mod p */
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/* find y^a * a^b */
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if (mp_exptmod(&key->y, &a, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = y^a mod p */
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if (mp_exptmod(&a, &b, &p, &a) != MP_OKAY) { goto error; } /* a = a^b mod p */
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if (mp_mulmod(&a, &tmp, &p, &a) != MP_OKAY) { goto error; } /* a = y^a * a^b mod p */
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/* y^a * a^b == g^m ??? */
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if (mp_cmp(&a, &m) == 0) {
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*stat = 1;
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}
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/* clean up */
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res = CRYPT_OK;
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goto done;
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error:
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res = CRYPT_MEM;
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done:
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mp_clear_multi(&tmp, &m, &g, &p, &b, &a, NULL);
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#ifdef CLEAN_STACK
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zeromem(md, sizeof(md));
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#endif
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return res;
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}
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