/* * Off-the-Record Messaging library * Copyright (C) 2004-2008 Ian Goldberg, Chris Alexander, Nikita Borisov * * * This library is free software; you can redistribute it and/or * modify it under the terms of version 2.1 of the GNU Lesser General * Public License as published by the Free Software Foundation. * * This library 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 * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ /* system headers */ #include #include #include /* libotr headers */ #include "b64.h" #include "privkey.h" #include "auth.h" #include "serial.h" /* * Initialize the fields of an OtrlAuthInfo (already allocated). */ void otrl_auth_new(OtrlAuthInfo *auth) { auth->authstate = OTRL_AUTHSTATE_NONE; otrl_dh_keypair_init(&(auth->our_dh)); auth->our_keyid = 0; auth->encgx = NULL; auth->encgx_len = 0; memset(auth->r, 0, 16); memset(auth->hashgx, 0, 32); auth->their_pub = NULL; auth->their_keyid = 0; auth->enc_c = NULL; auth->enc_cp = NULL; auth->mac_m1 = NULL; auth->mac_m1p = NULL; auth->mac_m2 = NULL; auth->mac_m2p = NULL; memset(auth->their_fingerprint, 0, 20); auth->initiated = 0; auth->protocol_version = 0; memset(auth->secure_session_id, 0, 20); auth->secure_session_id_len = 0; auth->lastauthmsg = NULL; } /* * Clear the fields of an OtrlAuthInfo (but leave it allocated). */ void otrl_auth_clear(OtrlAuthInfo *auth) { auth->authstate = OTRL_AUTHSTATE_NONE; otrl_dh_keypair_free(&(auth->our_dh)); auth->our_keyid = 0; free(auth->encgx); auth->encgx = NULL; auth->encgx_len = 0; memset(auth->r, 0, 16); memset(auth->hashgx, 0, 32); gcry_mpi_release(auth->their_pub); auth->their_pub = NULL; auth->their_keyid = 0; gcry_cipher_close(auth->enc_c); gcry_cipher_close(auth->enc_cp); gcry_md_close(auth->mac_m1); gcry_md_close(auth->mac_m1p); gcry_md_close(auth->mac_m2); gcry_md_close(auth->mac_m2p); auth->enc_c = NULL; auth->enc_cp = NULL; auth->mac_m1 = NULL; auth->mac_m1p = NULL; auth->mac_m2 = NULL; auth->mac_m2p = NULL; memset(auth->their_fingerprint, 0, 20); auth->initiated = 0; auth->protocol_version = 0; memset(auth->secure_session_id, 0, 20); auth->secure_session_id_len = 0; free(auth->lastauthmsg); auth->lastauthmsg = NULL; } /* * Start a fresh AKE (version 2) using the given OtrlAuthInfo. Generate * a fresh DH keypair to use. If no error is returned, the message to * transmit will be contained in auth->lastauthmsg. */ gcry_error_t otrl_auth_start_v2(OtrlAuthInfo *auth) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); const enum gcry_mpi_format format = GCRYMPI_FMT_USG; size_t npub; gcry_cipher_hd_t enc = NULL; unsigned char ctr[16]; unsigned char *buf, *bufp; size_t buflen, lenp; /* Clear out this OtrlAuthInfo and start over */ otrl_auth_clear(auth); auth->initiated = 1; otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh)); auth->our_keyid = 1; /* Pick an encryption key */ gcry_randomize(auth->r, 16, GCRY_STRONG_RANDOM); /* Allocate space for the encrypted g^x */ gcry_mpi_print(format, NULL, 0, &npub, auth->our_dh.pub); auth->encgx = malloc(4+npub); if (auth->encgx == NULL) goto memerr; auth->encgx_len = 4+npub; bufp = auth->encgx; lenp = auth->encgx_len; write_mpi(auth->our_dh.pub, npub, "g^x"); assert(lenp == 0); /* Hash g^x */ gcry_md_hash_buffer(GCRY_MD_SHA256, auth->hashgx, auth->encgx, auth->encgx_len); /* Encrypt g^x using the key r */ err = gcry_cipher_open(&enc, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR, GCRY_CIPHER_SECURE); if (err) goto err; err = gcry_cipher_setkey(enc, auth->r, 16); if (err) goto err; memset(ctr, 0, 16); err = gcry_cipher_setctr(enc, ctr, 16); if (err) goto err; err = gcry_cipher_encrypt(enc, auth->encgx, auth->encgx_len, NULL, 0); if (err) goto err; gcry_cipher_close(enc); enc = NULL; /* Now serialize the message */ lenp = 3 + 4 + auth->encgx_len + 4 + 32; bufp = malloc(lenp); if (bufp == NULL) goto memerr; buf = bufp; buflen = lenp; memmove(bufp, "\x00\x02\x02", 3); /* header */ debug_data("Header", bufp, 3); bufp += 3; lenp -= 3; /* Encrypted g^x */ write_int(auth->encgx_len); debug_int("Enc gx len", bufp-4); memmove(bufp, auth->encgx, auth->encgx_len); debug_data("Enc gx", bufp, auth->encgx_len); bufp += auth->encgx_len; lenp -= auth->encgx_len; /* Hashed g^x */ write_int(32); debug_int("hashgx len", bufp-4); memmove(bufp, auth->hashgx, 32); debug_data("hashgx", bufp, 32); bufp += 32; lenp -= 32; assert(lenp == 0); auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen); free(buf); if (auth->lastauthmsg == NULL) goto memerr; auth->authstate = OTRL_AUTHSTATE_AWAITING_DHKEY; return err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: otrl_auth_clear(auth); gcry_cipher_close(enc); return err; } /* * Create a D-H Key Message using the our_dh value in the given auth, * and store it in auth->lastauthmsg. */ static gcry_error_t create_key_message(OtrlAuthInfo *auth) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); const enum gcry_mpi_format format = GCRYMPI_FMT_USG; unsigned char *buf, *bufp; size_t buflen, lenp; size_t npub; gcry_mpi_print(format, NULL, 0, &npub, auth->our_dh.pub); buflen = 3 + 4 + npub; buf = malloc(buflen); if (buf == NULL) goto memerr; bufp = buf; lenp = buflen; memmove(bufp, "\x00\x02\x0a", 3); /* header */ debug_data("Header", bufp, 3); bufp += 3; lenp -= 3; /* g^y */ write_mpi(auth->our_dh.pub, npub, "g^y"); assert(lenp == 0); free(auth->lastauthmsg); auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen); free(buf); if (auth->lastauthmsg == NULL) goto memerr; return err; memerr: err = gcry_error(GPG_ERR_ENOMEM); return err; } /* * Handle an incoming D-H Commit Message. If no error is returned, the * message to send will be left in auth->lastauthmsg. Generate a fresh * keypair to use. */ gcry_error_t otrl_auth_handle_commit(OtrlAuthInfo *auth, const char *commitmsg) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp = NULL, *encbuf = NULL; unsigned char hashbuf[32]; size_t buflen, lenp, enclen, hashlen; int res; res = otrl_base64_otr_decode(commitmsg, &buf, &buflen); if (res == -1) goto memerr; if (res == -2) goto invval; bufp = buf; lenp = buflen; /* Header */ require_len(3); if (memcmp(bufp, "\x00\x02\x02", 3)) goto invval; bufp += 3; lenp -= 3; /* Encrypted g^x */ read_int(enclen); require_len(enclen); encbuf = malloc(enclen); if (encbuf == NULL && enclen > 0) goto memerr; memmove(encbuf, bufp, enclen); bufp += enclen; lenp -= enclen; /* Hashed g^x */ read_int(hashlen); if (hashlen != 32) goto invval; require_len(32); memmove(hashbuf, bufp, 32); bufp += 32; lenp -= 32; if (lenp != 0) goto invval; free(buf); buf = NULL; switch(auth->authstate) { case OTRL_AUTHSTATE_NONE: case OTRL_AUTHSTATE_AWAITING_SIG: case OTRL_AUTHSTATE_V1_SETUP: /* Store the incoming information */ otrl_auth_clear(auth); otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh)); auth->our_keyid = 1; auth->encgx = encbuf; encbuf = NULL; auth->encgx_len = enclen; memmove(auth->hashgx, hashbuf, 32); /* Create a D-H Key Message */ err = create_key_message(auth); if (err) goto err; auth->authstate = OTRL_AUTHSTATE_AWAITING_REVEALSIG; break; case OTRL_AUTHSTATE_AWAITING_DHKEY: /* We sent a D-H Commit Message, and we also received one * back. Compare the hashgx values to see which one wins. */ if (memcmp(auth->hashgx, hashbuf, 32) > 0) { /* Ours wins. Ignore the message we received, and just * resend the same D-H Commit message again. */ free(encbuf); encbuf = NULL; } else { /* Ours loses. Use the incoming parameters instead. */ otrl_auth_clear(auth); otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh)); auth->our_keyid = 1; auth->encgx = encbuf; encbuf = NULL; auth->encgx_len = enclen; memmove(auth->hashgx, hashbuf, 32); /* Create a D-H Key Message */ err = create_key_message(auth); if (err) goto err; auth->authstate = OTRL_AUTHSTATE_AWAITING_REVEALSIG; } break; case OTRL_AUTHSTATE_AWAITING_REVEALSIG: /* Use the incoming parameters, but just retransmit the old * D-H Key Message. */ free(auth->encgx); auth->encgx = encbuf; encbuf = NULL; auth->encgx_len = enclen; memmove(auth->hashgx, hashbuf, 32); break; } return err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); free(encbuf); return err; } /* * Calculate the encrypted part of the Reveal Signature and Signature * Messages, given a MAC key, an encryption key, two DH public keys, an * authentication public key (contained in an OtrlPrivKey structure), * and a keyid. If no error is returned, *authbufp will point to the * result, and *authlenp will point to its length. */ static gcry_error_t calculate_pubkey_auth(unsigned char **authbufp, size_t *authlenp, gcry_md_hd_t mackey, gcry_cipher_hd_t enckey, gcry_mpi_t our_dh_pub, gcry_mpi_t their_dh_pub, OtrlPrivKey *privkey, unsigned int keyid) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); const enum gcry_mpi_format format = GCRYMPI_FMT_USG; size_t ourpublen, theirpublen, totallen, lenp; unsigned char *buf = NULL, *bufp = NULL; unsigned char macbuf[32]; unsigned char *sigbuf = NULL; size_t siglen; /* How big are the DH public keys? */ gcry_mpi_print(format, NULL, 0, &ourpublen, our_dh_pub); gcry_mpi_print(format, NULL, 0, &theirpublen, their_dh_pub); /* How big is the total structure to be MAC'd? */ totallen = 4 + ourpublen + 4 + theirpublen + 2 + privkey->pubkey_datalen + 4; buf = malloc(totallen); if (buf == NULL) goto memerr; bufp = buf; lenp = totallen; /* Write the data to be MAC'd */ write_mpi(our_dh_pub, ourpublen, "Our DH pubkey"); write_mpi(their_dh_pub, theirpublen, "Their DH pubkey"); bufp[0] = ((privkey->pubkey_type) >> 16) & 0xff; bufp[1] = (privkey->pubkey_type) & 0xff; bufp += 2; lenp -= 2; memmove(bufp, privkey->pubkey_data, privkey->pubkey_datalen); debug_data("Pubkey", bufp, privkey->pubkey_datalen); bufp += privkey->pubkey_datalen; lenp -= privkey->pubkey_datalen; write_int(keyid); debug_int("Keyid", bufp-4); assert(lenp == 0); /* Do the MAC */ gcry_md_reset(mackey); gcry_md_write(mackey, buf, totallen); memmove(macbuf, gcry_md_read(mackey, GCRY_MD_SHA256), 32); free(buf); buf = NULL; /* Sign the MAC */ err = otrl_privkey_sign(&sigbuf, &siglen, privkey, macbuf, 32); if (err) goto err; /* Calculate the total size of the structure to be encrypted */ totallen = 2 + privkey->pubkey_datalen + 4 + siglen; buf = malloc(totallen); if (buf == NULL) goto memerr; bufp = buf; lenp = totallen; /* Write the data to be encrypted */ bufp[0] = ((privkey->pubkey_type) >> 16) & 0xff; bufp[1] = (privkey->pubkey_type) & 0xff; bufp += 2; lenp -= 2; memmove(bufp, privkey->pubkey_data, privkey->pubkey_datalen); debug_data("Pubkey", bufp, privkey->pubkey_datalen); bufp += privkey->pubkey_datalen; lenp -= privkey->pubkey_datalen; write_int(keyid); debug_int("Keyid", bufp-4); memmove(bufp, sigbuf, siglen); debug_data("Signature", bufp, siglen); bufp += siglen; lenp -= siglen; free(sigbuf); sigbuf = NULL; assert(lenp == 0); /* Now do the encryption */ err = gcry_cipher_encrypt(enckey, buf, totallen, NULL, 0); if (err) goto err; *authbufp = buf; buf = NULL; *authlenp = totallen; return err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); free(sigbuf); return err; } /* * Decrypt the authenticator in the Reveal Signature and Signature * Messages, given a MAC key, and encryption key, and two DH public * keys. The fingerprint of the received public key will get put into * fingerprintbufp, and the received keyid will get put in *keyidp. * The encrypted data pointed to by authbuf will be decrypted in place. */ static gcry_error_t check_pubkey_auth(unsigned char fingerprintbufp[20], unsigned int *keyidp, unsigned char *authbuf, size_t authlen, gcry_md_hd_t mackey, gcry_cipher_hd_t enckey, gcry_mpi_t our_dh_pub, gcry_mpi_t their_dh_pub) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); const enum gcry_mpi_format format = GCRYMPI_FMT_USG; size_t ourpublen, theirpublen, totallen, lenp; unsigned char *buf = NULL, *bufp = NULL; unsigned char macbuf[32]; unsigned short pubkey_type; gcry_mpi_t p,q,g,y; gcry_sexp_t pubs = NULL; unsigned int received_keyid; unsigned char *fingerprintstart, *fingerprintend, *sigbuf; size_t siglen; /* Start by decrypting it */ err = gcry_cipher_decrypt(enckey, authbuf, authlen, NULL, 0); if (err) goto err; bufp = authbuf; lenp = authlen; /* Get the public key and calculate its fingerprint */ require_len(2); pubkey_type = (bufp[0] << 8) + bufp[1]; bufp += 2; lenp -= 2; if (pubkey_type != OTRL_PUBKEY_TYPE_DSA) goto invval; fingerprintstart = bufp; read_mpi(p); read_mpi(q); read_mpi(g); read_mpi(y); fingerprintend = bufp; gcry_md_hash_buffer(GCRY_MD_SHA1, fingerprintbufp, fingerprintstart, fingerprintend-fingerprintstart); gcry_sexp_build(&pubs, NULL, "(public-key (dsa (p %m)(q %m)(g %m)(y %m)))", p, q, g, y); gcry_mpi_release(p); gcry_mpi_release(q); gcry_mpi_release(g); gcry_mpi_release(y); /* Get the keyid */ read_int(received_keyid); if (received_keyid == 0) goto invval; /* Get the signature */ sigbuf = bufp; siglen = lenp; /* How big are the DH public keys? */ gcry_mpi_print(format, NULL, 0, &ourpublen, our_dh_pub); gcry_mpi_print(format, NULL, 0, &theirpublen, their_dh_pub); /* Now calculate the message to be MAC'd. */ totallen = 4 + ourpublen + 4 + theirpublen + 2 + (fingerprintend - fingerprintstart) + 4; buf = malloc(totallen); if (buf == NULL) goto memerr; bufp = buf; lenp = totallen; write_mpi(their_dh_pub, theirpublen, "Their DH pubkey"); write_mpi(our_dh_pub, ourpublen, "Our DH pubkey"); bufp[0] = (pubkey_type >> 16) & 0xff; bufp[1] = pubkey_type & 0xff; bufp += 2; lenp -= 2; memmove(bufp, fingerprintstart, fingerprintend - fingerprintstart); debug_data("Pubkey", bufp, fingerprintend - fingerprintstart); bufp += fingerprintend - fingerprintstart; lenp -= fingerprintend - fingerprintstart; write_int(received_keyid); debug_int("Keyid", bufp-4); assert(lenp == 0); /* Do the MAC */ gcry_md_reset(mackey); gcry_md_write(mackey, buf, totallen); memmove(macbuf, gcry_md_read(mackey, GCRY_MD_SHA256), 32); free(buf); buf = NULL; /* Verify the signature on the MAC */ err = otrl_privkey_verify(sigbuf, siglen, pubkey_type, pubs, macbuf, 32); if (err) goto err; gcry_sexp_release(pubs); pubs = NULL; /* Everything checked out */ *keyidp = received_keyid; return err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); gcry_sexp_release(pubs); return err; } /* * Create a Reveal Signature Message using the values in the given auth, * and store it in auth->lastauthmsg. Use the given privkey to sign the * message. */ static gcry_error_t create_revealsig_message(OtrlAuthInfo *auth, OtrlPrivKey *privkey) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp, *startmac; size_t buflen, lenp; unsigned char *authbuf = NULL; size_t authlen; /* Get the encrypted authenticator */ err = calculate_pubkey_auth(&authbuf, &authlen, auth->mac_m1, auth->enc_c, auth->our_dh.pub, auth->their_pub, privkey, auth->our_keyid); if (err) goto err; buflen = 3 + 4 + 16 + 4 + authlen + 20; buf = malloc(buflen); if (buf == NULL) goto memerr; bufp = buf; lenp = buflen; memmove(bufp, "\x00\x02\x11", 3); /* header */ debug_data("Header", bufp, 3); bufp += 3; lenp -= 3; /* r */ write_int(16); memmove(bufp, auth->r, 16); debug_data("r", bufp, 16); bufp += 16; lenp -= 16; /* Encrypted authenticator */ startmac = bufp; write_int(authlen); memmove(bufp, authbuf, authlen); debug_data("auth", bufp, authlen); bufp += authlen; lenp -= authlen; free(authbuf); authbuf = NULL; /* MAC it, but only take the first 20 bytes */ gcry_md_reset(auth->mac_m2); gcry_md_write(auth->mac_m2, startmac, bufp - startmac); memmove(bufp, gcry_md_read(auth->mac_m2, GCRY_MD_SHA256), 20); debug_data("MAC", bufp, 20); bufp += 20; lenp -= 20; assert(lenp == 0); free(auth->lastauthmsg); auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen); if (auth->lastauthmsg == NULL) goto memerr; free(buf); buf = NULL; return err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); free(authbuf); return err; } /* * Create a Signature Message using the values in the given auth, and * store it in auth->lastauthmsg. Use the given privkey to sign the * message. */ static gcry_error_t create_signature_message(OtrlAuthInfo *auth, OtrlPrivKey *privkey) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp, *startmac; size_t buflen, lenp; unsigned char *authbuf = NULL; size_t authlen; /* Get the encrypted authenticator */ err = calculate_pubkey_auth(&authbuf, &authlen, auth->mac_m1p, auth->enc_cp, auth->our_dh.pub, auth->their_pub, privkey, auth->our_keyid); if (err) goto err; buflen = 3 + 4 + authlen + 20; buf = malloc(buflen); if (buf == NULL) goto memerr; bufp = buf; lenp = buflen; memmove(bufp, "\x00\x02\x12", 3); /* header */ debug_data("Header", bufp, 3); bufp += 3; lenp -= 3; /* Encrypted authenticator */ startmac = bufp; write_int(authlen); memmove(bufp, authbuf, authlen); debug_data("auth", bufp, authlen); bufp += authlen; lenp -= authlen; free(authbuf); authbuf = NULL; /* MAC it, but only take the first 20 bytes */ gcry_md_reset(auth->mac_m2p); gcry_md_write(auth->mac_m2p, startmac, bufp - startmac); memmove(bufp, gcry_md_read(auth->mac_m2p, GCRY_MD_SHA256), 20); debug_data("MAC", bufp, 20); bufp += 20; lenp -= 20; assert(lenp == 0); free(auth->lastauthmsg); auth->lastauthmsg = otrl_base64_otr_encode(buf, buflen); if (auth->lastauthmsg == NULL) goto memerr; free(buf); buf = NULL; return err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); free(authbuf); return err; } /* * Handle an incoming D-H Key Message. If no error is returned, and * *havemsgp is 1, the message to sent will be left in auth->lastauthmsg. * Use the given private authentication key to sign messages. */ gcry_error_t otrl_auth_handle_key(OtrlAuthInfo *auth, const char *keymsg, int *havemsgp, OtrlPrivKey *privkey) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp = NULL; size_t buflen, lenp; gcry_mpi_t incoming_pub = NULL; int res; *havemsgp = 0; res = otrl_base64_otr_decode(keymsg, &buf, &buflen); if (res == -1) goto memerr; if (res == -2) goto invval; bufp = buf; lenp = buflen; /* Header */ if (memcmp(bufp, "\x00\x02\x0a", 3)) goto invval; bufp += 3; lenp -= 3; /* g^y */ read_mpi(incoming_pub); if (lenp != 0) goto invval; free(buf); buf = NULL; switch(auth->authstate) { case OTRL_AUTHSTATE_AWAITING_DHKEY: /* Store the incoming public key */ gcry_mpi_release(auth->their_pub); auth->their_pub = incoming_pub; incoming_pub = NULL; /* Compute the encryption and MAC keys */ err = otrl_dh_compute_v2_auth_keys(&(auth->our_dh), auth->their_pub, auth->secure_session_id, &(auth->secure_session_id_len), &(auth->enc_c), &(auth->enc_cp), &(auth->mac_m1), &(auth->mac_m1p), &(auth->mac_m2), &(auth->mac_m2p)); if (err) goto err; /* Create the Reveal Signature Message */ err = create_revealsig_message(auth, privkey); if (err) goto err; *havemsgp = 1; auth->authstate = OTRL_AUTHSTATE_AWAITING_SIG; break; case OTRL_AUTHSTATE_AWAITING_SIG: if (gcry_mpi_cmp(incoming_pub, auth->their_pub) == 0) { /* Retransmit the Reveal Signature Message */ *havemsgp = 1; } else { /* Ignore this message */ *havemsgp = 0; } break; case OTRL_AUTHSTATE_NONE: case OTRL_AUTHSTATE_AWAITING_REVEALSIG: case OTRL_AUTHSTATE_V1_SETUP: /* Ignore this message */ *havemsgp = 0; break; } gcry_mpi_release(incoming_pub); return err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); gcry_mpi_release(incoming_pub); return err; } /* * Handle an incoming Reveal Signature Message. If no error is * returned, and *havemsgp is 1, the message to be sent will be left in * auth->lastauthmsg. Use the given private authentication key to sign * messages. Call the auth_succeeded callback if authentication is * successful. */ gcry_error_t otrl_auth_handle_revealsig(OtrlAuthInfo *auth, const char *revealmsg, int *havemsgp, OtrlPrivKey *privkey, gcry_error_t (*auth_succeeded)(const OtrlAuthInfo *auth, void *asdata), void *asdata) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp = NULL, *gxbuf = NULL; unsigned char *authstart, *authend, *macstart; size_t buflen, lenp, rlen, authlen; gcry_cipher_hd_t enc = NULL; gcry_mpi_t incoming_pub = NULL; unsigned char ctr[16], hashbuf[32]; int res; *havemsgp = 0; res = otrl_base64_otr_decode(revealmsg, &buf, &buflen); if (res == -1) goto memerr; if (res == -2) goto invval; bufp = buf; lenp = buflen; /* Header */ if (memcmp(bufp, "\x00\x02\x11", 3)) goto invval; bufp += 3; lenp -= 3; /* r */ read_int(rlen); if (rlen != 16) goto invval; require_len(rlen); memmove(auth->r, bufp, rlen); bufp += rlen; lenp -= rlen; /* auth */ authstart = bufp; read_int(authlen); require_len(authlen); bufp += authlen; lenp -= authlen; authend = bufp; /* MAC */ require_len(20); macstart = bufp; bufp += 20; lenp -= 20; if (lenp != 0) goto invval; switch(auth->authstate) { case OTRL_AUTHSTATE_AWAITING_REVEALSIG: gxbuf = malloc(auth->encgx_len); if (auth->encgx_len && gxbuf == NULL) goto memerr; /* Use r to decrypt the value of g^x we received earlier */ err = gcry_cipher_open(&enc, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR, GCRY_CIPHER_SECURE); if (err) goto err; err = gcry_cipher_setkey(enc, auth->r, 16); if (err) goto err; memset(ctr, 0, 16); err = gcry_cipher_setctr(enc, ctr, 16); if (err) goto err; err = gcry_cipher_decrypt(enc, gxbuf, auth->encgx_len, auth->encgx, auth->encgx_len); if (err) goto err; gcry_cipher_close(enc); enc = NULL; /* Check the hash */ gcry_md_hash_buffer(GCRY_MD_SHA256, hashbuf, gxbuf, auth->encgx_len); if (memcmp(hashbuf, auth->hashgx, 32)) goto decfail; /* Extract g^x */ bufp = gxbuf; lenp = auth->encgx_len; read_mpi(incoming_pub); free(gxbuf); gxbuf = NULL; if (lenp != 0) goto invval; gcry_mpi_release(auth->their_pub); auth->their_pub = incoming_pub; incoming_pub = NULL; /* Compute the encryption and MAC keys */ err = otrl_dh_compute_v2_auth_keys(&(auth->our_dh), auth->their_pub, auth->secure_session_id, &(auth->secure_session_id_len), &(auth->enc_c), &(auth->enc_cp), &(auth->mac_m1), &(auth->mac_m1p), &(auth->mac_m2), &(auth->mac_m2p)); if (err) goto err; /* Check the MAC */ gcry_md_reset(auth->mac_m2); gcry_md_write(auth->mac_m2, authstart, authend - authstart); if (memcmp(macstart, gcry_md_read(auth->mac_m2, GCRY_MD_SHA256), 20)) goto invval; /* Check the auth */ err = check_pubkey_auth(auth->their_fingerprint, &(auth->their_keyid), authstart + 4, authend - authstart - 4, auth->mac_m1, auth->enc_c, auth->our_dh.pub, auth->their_pub); if (err) goto err; authstart = NULL; authend = NULL; macstart = NULL; free(buf); buf = NULL; /* Create the Signature Message */ err = create_signature_message(auth, privkey); if (err) goto err; /* No error? Then we've completed our end of the * authentication. */ auth->protocol_version = 2; auth->session_id_half = OTRL_SESSIONID_SECOND_HALF_BOLD; if (auth_succeeded) err = auth_succeeded(auth, asdata); *havemsgp = 1; auth->our_keyid = 0; auth->authstate = OTRL_AUTHSTATE_NONE; break; case OTRL_AUTHSTATE_NONE: case OTRL_AUTHSTATE_AWAITING_DHKEY: case OTRL_AUTHSTATE_AWAITING_SIG: case OTRL_AUTHSTATE_V1_SETUP: /* Ignore this message */ *havemsgp = 0; free(buf); buf = NULL; break; } return err; decfail: err = gcry_error(GPG_ERR_NO_ERROR); goto err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); free(gxbuf); gcry_cipher_close(enc); gcry_mpi_release(incoming_pub); return err; } /* * Handle an incoming Signature Message. If no error is returned, and * *havemsgp is 1, the message to be sent will be left in * auth->lastauthmsg. Call the auth_succeeded callback if * authentication is successful. */ gcry_error_t otrl_auth_handle_signature(OtrlAuthInfo *auth, const char *sigmsg, int *havemsgp, gcry_error_t (*auth_succeeded)(const OtrlAuthInfo *auth, void *asdata), void *asdata) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp = NULL; unsigned char *authstart, *authend, *macstart; size_t buflen, lenp, authlen; int res; *havemsgp = 0; res = otrl_base64_otr_decode(sigmsg, &buf, &buflen); if (res == -1) goto memerr; if (res == -2) goto invval; bufp = buf; lenp = buflen; /* Header */ if (memcmp(bufp, "\x00\x02\x12", 3)) goto invval; bufp += 3; lenp -= 3; /* auth */ authstart = bufp; read_int(authlen); require_len(authlen); bufp += authlen; lenp -= authlen; authend = bufp; /* MAC */ require_len(20); macstart = bufp; bufp += 20; lenp -= 20; if (lenp != 0) goto invval; switch(auth->authstate) { case OTRL_AUTHSTATE_AWAITING_SIG: /* Check the MAC */ gcry_md_reset(auth->mac_m2p); gcry_md_write(auth->mac_m2p, authstart, authend - authstart); if (memcmp(macstart, gcry_md_read(auth->mac_m2p, GCRY_MD_SHA256), 20)) goto invval; /* Check the auth */ err = check_pubkey_auth(auth->their_fingerprint, &(auth->their_keyid), authstart + 4, authend - authstart - 4, auth->mac_m1p, auth->enc_cp, auth->our_dh.pub, auth->their_pub); if (err) goto err; authstart = NULL; authend = NULL; macstart = NULL; free(buf); buf = NULL; /* No error? Then we've completed our end of the * authentication. */ auth->protocol_version = 2; auth->session_id_half = OTRL_SESSIONID_FIRST_HALF_BOLD; if (auth_succeeded) err = auth_succeeded(auth, asdata); free(auth->lastauthmsg); auth->lastauthmsg = NULL; *havemsgp = 1; auth->our_keyid = 0; auth->authstate = OTRL_AUTHSTATE_NONE; break; case OTRL_AUTHSTATE_NONE: case OTRL_AUTHSTATE_AWAITING_DHKEY: case OTRL_AUTHSTATE_AWAITING_REVEALSIG: case OTRL_AUTHSTATE_V1_SETUP: /* Ignore this message */ *havemsgp = 0; break; } return err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); return err; } /* Version 1 routines, for compatibility */ /* * Create a verion 1 Key Exchange Message using the values in the given * auth, and store it in auth->lastauthmsg. Set the Reply field to the * given value, and use the given privkey to sign the message. */ static gcry_error_t create_v1_key_exchange_message(OtrlAuthInfo *auth, unsigned char reply, OtrlPrivKey *privkey) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); const enum gcry_mpi_format format = GCRYMPI_FMT_USG; unsigned char *buf = NULL, *bufp = NULL, *sigbuf = NULL; size_t lenp, ourpublen, totallen, siglen; unsigned char hashbuf[20]; if (privkey->pubkey_type != OTRL_PUBKEY_TYPE_DSA) { return gpg_error(GPG_ERR_INV_VALUE); } /* How big is the DH public key? */ gcry_mpi_print(format, NULL, 0, &ourpublen, auth->our_dh.pub); totallen = 3 + 1 + privkey->pubkey_datalen + 4 + 4 + ourpublen + 40; buf = malloc(totallen); if (buf == NULL) goto memerr; bufp = buf; lenp = totallen; memmove(bufp, "\x00\x01\x0a", 3); /* header */ debug_data("Header", bufp, 3); bufp += 3; lenp -= 3; bufp[0] = reply; debug_data("Reply", bufp, 1); bufp += 1; lenp -= 1; memmove(bufp, privkey->pubkey_data, privkey->pubkey_datalen); debug_data("Pubkey", bufp, privkey->pubkey_datalen); bufp += privkey->pubkey_datalen; lenp -= privkey->pubkey_datalen; write_int(auth->our_keyid); debug_int("Keyid", bufp-4); write_mpi(auth->our_dh.pub, ourpublen, "D-H y"); /* Hash all the data written so far, and sign the hash */ gcry_md_hash_buffer(GCRY_MD_SHA1, hashbuf, buf, bufp - buf); err = otrl_privkey_sign(&sigbuf, &siglen, privkey, hashbuf, 20); if (err) goto err; if (siglen != 40) goto invval; memmove(bufp, sigbuf, 40); debug_data("Signature", bufp, 40); bufp += 40; lenp -= 40; free(sigbuf); sigbuf = NULL; assert(lenp == 0); free(auth->lastauthmsg); auth->lastauthmsg = otrl_base64_otr_encode(buf, totallen); if (auth->lastauthmsg == NULL) goto memerr; free(buf); buf = NULL; return err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); free(sigbuf); return err; } /* * Start a fresh AKE (version 1) using the given OtrlAuthInfo. If * our_dh is NULL, generate a fresh DH keypair to use. Otherwise, use a * copy of the one passed (with the given keyid). Use the given private * key to sign the message. If no error is returned, the message to * transmit will be contained in auth->lastauthmsg. */ gcry_error_t otrl_auth_start_v1(OtrlAuthInfo *auth, DH_keypair *our_dh, unsigned int our_keyid, OtrlPrivKey *privkey) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); /* Clear out this OtrlAuthInfo and start over */ otrl_auth_clear(auth); auth->initiated = 1; /* Import the given DH keypair, or else create a fresh one */ if (our_dh) { otrl_dh_keypair_copy(&(auth->our_dh), our_dh); auth->our_keyid = our_keyid; } else { otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh)); auth->our_keyid = 1; } err = create_v1_key_exchange_message(auth, 0, privkey); if (!err) { auth->authstate = OTRL_AUTHSTATE_V1_SETUP; } return err; } /* * Handle an incoming v1 Key Exchange Message. If no error is returned, * and *havemsgp is 1, the message to be sent will be left in * auth->lastauthmsg. Use the given private authentication key to sign * messages. Call the auth_secceeded callback if authentication is * successful. If non-NULL, use a copy of the given D-H keypair, with * the given keyid. */ gcry_error_t otrl_auth_handle_v1_key_exchange(OtrlAuthInfo *auth, const char *keyexchmsg, int *havemsgp, OtrlPrivKey *privkey, DH_keypair *our_dh, unsigned int our_keyid, gcry_error_t (*auth_succeeded)(const OtrlAuthInfo *auth, void *asdata), void *asdata) { gcry_error_t err = gcry_error(GPG_ERR_NO_ERROR); unsigned char *buf = NULL, *bufp = NULL; unsigned char *fingerprintstart, *fingerprintend; unsigned char fingerprintbuf[20], hashbuf[20]; gcry_mpi_t p, q, g, y, received_pub = NULL; gcry_sexp_t pubs = NULL; size_t buflen, lenp; unsigned char received_reply; unsigned int received_keyid; int res; *havemsgp = 0; res = otrl_base64_otr_decode(keyexchmsg, &buf, &buflen); if (res == -1) goto memerr; if (res == -2) goto invval; bufp = buf; lenp = buflen; /* Header */ require_len(3); if (memcmp(bufp, "\x00\x01\x0a", 3)) goto invval; bufp += 3; lenp -= 3; /* Reply */ require_len(1); received_reply = bufp[0]; bufp += 1; lenp -= 1; /* Public Key */ fingerprintstart = bufp; read_mpi(p); read_mpi(q); read_mpi(g); read_mpi(y); fingerprintend = bufp; gcry_md_hash_buffer(GCRY_MD_SHA1, fingerprintbuf, fingerprintstart, fingerprintend-fingerprintstart); gcry_sexp_build(&pubs, NULL, "(public-key (dsa (p %m)(q %m)(g %m)(y %m)))", p, q, g, y); gcry_mpi_release(p); gcry_mpi_release(q); gcry_mpi_release(g); gcry_mpi_release(y); /* keyid */ read_int(received_keyid); if (received_keyid == 0) goto invval; /* D-H pubkey */ read_mpi(received_pub); /* Verify the signature */ if (lenp != 40) goto invval; gcry_md_hash_buffer(GCRY_MD_SHA1, hashbuf, buf, bufp - buf); err = otrl_privkey_verify(bufp, lenp, OTRL_PUBKEY_TYPE_DSA, pubs, hashbuf, 20); if (err) goto err; gcry_sexp_release(pubs); pubs = NULL; free(buf); buf = NULL; if (auth->authstate != OTRL_AUTHSTATE_V1_SETUP && received_reply == 0x01) { /* They're replying to something we never sent. We must be * logged in more than once; ignore the message. */ err = gpg_error(GPG_ERR_NO_ERROR); goto err; } if (auth->authstate != OTRL_AUTHSTATE_V1_SETUP) { /* Clear the auth and start over */ otrl_auth_clear(auth); } /* Everything checked out */ auth->their_keyid = received_keyid; gcry_mpi_release(auth->their_pub); auth->their_pub = received_pub; received_pub = NULL; memmove(auth->their_fingerprint, fingerprintbuf, 20); if (received_reply == 0x01) { /* Don't send a reply to this. */ *havemsgp = 0; } else { /* Import the given DH keypair, or else create a fresh one */ if (our_dh) { otrl_dh_keypair_copy(&(auth->our_dh), our_dh); auth->our_keyid = our_keyid; } else if (auth->our_keyid == 0) { otrl_dh_gen_keypair(DH1536_GROUP_ID, &(auth->our_dh)); auth->our_keyid = 1; } /* Reply with our own Key Exchange Message */ err = create_v1_key_exchange_message(auth, 1, privkey); if (err) goto err; *havemsgp = 1; } /* Compute the session id */ err = otrl_dh_compute_v1_session_id(&(auth->our_dh), auth->their_pub, auth->secure_session_id, &(auth->secure_session_id_len), &(auth->session_id_half)); if (err) goto err; /* We've completed our end of the authentication */ auth->protocol_version = 1; if (auth_succeeded) err = auth_succeeded(auth, asdata); auth->our_keyid = 0; auth->authstate = OTRL_AUTHSTATE_NONE; return err; invval: err = gcry_error(GPG_ERR_INV_VALUE); goto err; memerr: err = gcry_error(GPG_ERR_ENOMEM); err: free(buf); gcry_sexp_release(pubs); gcry_mpi_release(received_pub); return err; } #ifdef OTRL_TESTING_AUTH #include "mem.h" #include "privkey.h" #define CHECK_ERR if (err) { printf("Error: %s\n", gcry_strerror(err)); return 1; } static gcry_error_t starting(const OtrlAuthInfo *auth, void *asdata) { char *name = asdata; fprintf(stderr, "\nStarting ENCRYPTED mode for %s (v%d).\n", name, auth->protocol_version); fprintf(stderr, "\nour_dh (%d):", auth->our_keyid); gcry_mpi_dump(auth->our_dh.pub); fprintf(stderr, "\ntheir_pub (%d):", auth->their_keyid); gcry_mpi_dump(auth->their_pub); debug_data("\nTheir fingerprint", auth->their_fingerprint, 20); debug_data("\nSecure session id", auth->secure_session_id, auth->secure_session_id_len); fprintf(stderr, "Sessionid half: %d\n\n", auth->session_id_half); return gpg_error(GPG_ERR_NO_ERROR); } int main(int argc, char **argv) { OtrlAuthInfo alice, bob; gcry_error_t err; int havemsg; OtrlUserState us; OtrlPrivKey *alicepriv, *bobpriv; otrl_mem_init(); otrl_dh_init(); otrl_auth_new(&alice); otrl_auth_new(&bob); us = otrl_userstate_create(); otrl_privkey_read(us, "/home/iang/.gaim/otr.private_key"); alicepriv = otrl_privkey_find(us, "oneeyedian", "prpl-oscar"); bobpriv = otrl_privkey_find(us, "otr4ian", "prpl-oscar"); printf("\n\n ***** V2 *****\n\n"); err = otrl_auth_start_v2(&bob, NULL, 0); CHECK_ERR printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg); err = otrl_auth_handle_commit(&alice, bob.lastauthmsg, NULL, 0); CHECK_ERR printf("\nAlice: %d\n%s\n\n", strlen(alice.lastauthmsg), alice.lastauthmsg); err = otrl_auth_handle_key(&bob, alice.lastauthmsg, &havemsg, bobpriv); CHECK_ERR if (havemsg) { printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg); } else { printf("\nIGNORE\n\n"); } err = otrl_auth_handle_revealsig(&alice, bob.lastauthmsg, &havemsg, alicepriv, starting, "Alice"); CHECK_ERR if (havemsg) { printf("\nAlice: %d\n%s\n\n", strlen(alice.lastauthmsg), alice.lastauthmsg); } else { printf("\nIGNORE\n\n"); } err = otrl_auth_handle_signature(&bob, alice.lastauthmsg, &havemsg, starting, "Bob"); CHECK_ERR printf("\n\n ***** V1 *****\n\n"); err = otrl_auth_start_v1(&bob, NULL, 0, bobpriv); CHECK_ERR printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg); err = otrl_auth_handle_v1_key_exchange(&alice, bob.lastauthmsg, &havemsg, alicepriv, NULL, 0, starting, "Alice"); CHECK_ERR if (havemsg) { printf("\nAlice: %d\n%s\n\n", strlen(alice.lastauthmsg), alice.lastauthmsg); } else { printf("\nIGNORE\n\n"); } err = otrl_auth_handle_v1_key_exchange(&bob, alice.lastauthmsg, &havemsg, bobpriv, NULL, 0, starting, "Bob"); CHECK_ERR if (havemsg) { printf("\nBob: %d\n%s\n\n", strlen(bob.lastauthmsg), bob.lastauthmsg); } else { printf("\nIGNORE\n\n"); } otrl_userstate_free(us); otrl_auth_clear(&alice); otrl_auth_clear(&bob); return 0; } #endif