diff options
Diffstat (limited to 'libotr/libotr-4.1.1/toolkit/sesskeys.c')
| -rw-r--r-- | libotr/libotr-4.1.1/toolkit/sesskeys.c | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/libotr/libotr-4.1.1/toolkit/sesskeys.c b/libotr/libotr-4.1.1/toolkit/sesskeys.c new file mode 100644 index 0000000..08649e6 --- /dev/null +++ b/libotr/libotr-4.1.1/toolkit/sesskeys.c @@ -0,0 +1,98 @@ +/* + * Off-the-Record Messaging Toolkit + * Copyright (C) 2004-2014 Ian Goldberg, David Goulet, Chris Alexander, + * Nikita Borisov + * <otr@cypherpunks.ca> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of version 2 of the GNU General Public License as + * published by the Free Software Foundation. + * + * 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 + */ + +/* system headers */ +#include <stdlib.h> + +/* libgcrypt headers */ +#include <gcrypt.h> + +static const char* DH1536_MODULUS_S = "0x" + "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" + "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" + "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" + "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" + "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D" + "C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F" + "83655D23DCA3AD961C62F356208552BB9ED529077096966D" + "670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF"; +static const int DH1536_MOD_LEN_BITS = 1536; +static const char *DH1536_GENERATOR_S = "0x02"; + +/* Generate the session id and the two encryption keys from our private + * DH key and their public DH key. Also indicate in *high_endp if we + * are the "high" end of the key exchange (set to 1) or the "low" end + * (set to 0) */ +void sesskeys_gen(unsigned char sessionid[20], unsigned char sendenc[16], + unsigned char rcvenc[16], int *high_endp, gcry_mpi_t *our_yp, + gcry_mpi_t our_x, gcry_mpi_t their_y) +{ + gcry_mpi_t modulus, generator, secretv; + unsigned char *secret; + size_t secretlen; + unsigned char hash[20]; + int is_high; + + gcry_mpi_scan(&modulus, GCRYMPI_FMT_HEX, + (const unsigned char *)DH1536_MODULUS_S, 0, NULL); + gcry_mpi_scan(&generator, GCRYMPI_FMT_HEX, + (const unsigned char *)DH1536_GENERATOR_S, 0, NULL); + *our_yp = gcry_mpi_snew(DH1536_MOD_LEN_BITS); + gcry_mpi_powm(*our_yp, generator, our_x, modulus); + secretv = gcry_mpi_snew(DH1536_MOD_LEN_BITS); + gcry_mpi_powm(secretv, their_y, our_x, modulus); + gcry_mpi_release(generator); + gcry_mpi_release(modulus); + gcry_mpi_print(GCRYMPI_FMT_USG, NULL, 0, &secretlen, secretv); + secret = malloc(secretlen + 5); + + secret[1] = (secretlen >> 24) & 0xff; + secret[2] = (secretlen >> 16) & 0xff; + secret[3] = (secretlen >> 8) & 0xff; + secret[4] = (secretlen) & 0xff; + gcry_mpi_print(GCRYMPI_FMT_USG, secret+5, secretlen, NULL, secretv); + gcry_mpi_release(secretv); + + is_high = (gcry_mpi_cmp(*our_yp, their_y) > 0); + + /* Calculate the session id */ + secret[0] = 0x00; + gcry_md_hash_buffer(GCRY_MD_SHA1, hash, secret, secretlen+5); + memmove(sessionid, hash, 20); + + /* Calculate the sending enc key */ + secret[0] = is_high ? 0x01 : 0x02; + gcry_md_hash_buffer(GCRY_MD_SHA1, hash, secret, secretlen+5); + memmove(sendenc, hash, 16); + + /* Calculate the receiving enc key */ + secret[0] = is_high ? 0x02 : 0x01; + gcry_md_hash_buffer(GCRY_MD_SHA1, hash, secret, secretlen+5); + memmove(rcvenc, hash, 16); + + *high_endp = is_high; + free(secret); +} + +/* Generate a MAC key from the corresponding encryption key */ +void sesskeys_make_mac(unsigned char mackey[20], unsigned char enckey[16]) +{ + gcry_md_hash_buffer(GCRY_MD_SHA1, mackey, enckey, 16); +} |