u_char * mac_compute(Mac *mac, u_int32_t seqno, u_char *data, int datalen) { static union { u_char m[EVP_MAX_MD_SIZE]; u_int64_t for_align; } u; u_char b[4]; u_char nonce[8]; if (mac->mac_len > sizeof(u)) fatal("mac_compute: mac too long %u %zu", mac->mac_len, sizeof(u)); switch (mac->type) { case SSH_DIGEST: put_u32(b, seqno); /* reset HMAC context */ if (ssh_hmac_init(mac->hmac_ctx, NULL, 0) < 0 || ssh_hmac_update(mac->hmac_ctx, b, sizeof(b)) < 0 || ssh_hmac_update(mac->hmac_ctx, data, datalen) < 0 || ssh_hmac_final(mac->hmac_ctx, u.m, sizeof(u.m)) < 0) fatal("ssh_hmac failed"); break; case SSH_UMAC: put_u64(nonce, seqno); umac_update(mac->umac_ctx, data, datalen); umac_final(mac->umac_ctx, u.m, nonce); break; case SSH_UMAC128: put_u64(nonce, seqno); umac128_update(mac->umac_ctx, data, datalen); umac128_final(mac->umac_ctx, u.m, nonce); break; default: fatal("mac_compute: unknown MAC type"); } return (u.m); }
/* cc -DTEST hmac.c digest.c buffer.c cleanup.c fatal.c log.c xmalloc.c -lcrypto */ static void hmac_test(void *key, size_t klen, void *m, size_t mlen, u_char *e, size_t elen) { struct ssh_hmac_ctx *ctx; size_t i; u_char digest[16]; if ((ctx = ssh_hmac_start(SSH_DIGEST_MD5)) == NULL) printf("ssh_hmac_start failed"); if (ssh_hmac_init(ctx, key, klen) < 0 || ssh_hmac_update(ctx, m, mlen) < 0 || ssh_hmac_final(ctx, digest, sizeof(digest)) < 0) printf("ssh_hmac_xxx failed"); ssh_hmac_free(ctx); if (memcmp(e, digest, elen)) { for (i = 0; i < elen; i++) printf("[%zd] %2.2x %2.2x\n", i, e[i], digest[i]); printf("mismatch\n"); } else printf("ok\n"); }
char * host_hash(const char *host, const char *name_from_hostfile, u_int src_len) { struct ssh_hmac_ctx *ctx; u_char salt[256], result[256]; char uu_salt[512], uu_result[512]; static char encoded[1024]; u_int i, len; len = ssh_digest_bytes(SSH_DIGEST_SHA1); if (name_from_hostfile == NULL) { /* Create new salt */ for (i = 0; i < len; i++) salt[i] = arc4random(); } else { /* Extract salt from known host entry */ if (extract_salt(name_from_hostfile, src_len, salt, sizeof(salt)) == -1) return (NULL); } if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL || ssh_hmac_init(ctx, salt, len) < 0 || ssh_hmac_update(ctx, host, strlen(host)) < 0 || ssh_hmac_final(ctx, result, sizeof(result))) fatal("%s: ssh_hmac failed", __func__); ssh_hmac_free(ctx); if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) fatal("%s: __b64_ntop failed", __func__); snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, HASH_DELIM, uu_result); return (encoded); }