static u_char *
derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
const u_char *shared_secret, u_int slen)
{
Buffer b;
struct ssh_digest_ctx *hashctx;
char c = id;
u_int have;
size_t mdsz;
u_char *digest;
if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
fatal("bad kex md size %zu", mdsz);
digest = xmalloc(roundup(need, mdsz));
buffer_init(&b);
buffer_append(&b, shared_secret, slen);
/* K1 = HASH(K || H || "A" || session_id) */
if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
fatal("%s: ssh_digest_start failed", __func__);
if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
ssh_digest_update(hashctx, hash, hashlen) != 0 ||
ssh_digest_update(hashctx, &c, 1) != 0 ||
ssh_digest_update(hashctx, kex->session_id,
kex->session_id_len) != 0)
fatal("%s: ssh_digest_update failed", __func__);
if (ssh_digest_final(hashctx, digest, mdsz) != 0)
fatal("%s: ssh_digest_final failed", __func__);
ssh_digest_free(hashctx);
/*
* expand key:
* Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
* Key = K1 || K2 || ... || Kn
*/
for (have = mdsz; need > have; have += mdsz) {
if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL)
fatal("%s: ssh_digest_start failed", __func__);
if (ssh_digest_update_buffer(hashctx, &b) != 0 ||
ssh_digest_update(hashctx, hash, hashlen) != 0 ||
ssh_digest_update(hashctx, digest, have) != 0)
fatal("%s: ssh_digest_update failed", __func__);
if (ssh_digest_final(hashctx, digest + have, mdsz) != 0)
fatal("%s: ssh_digest_final failed", __func__);
ssh_digest_free(hashctx);
}
buffer_free(&b);
#ifdef DEBUG_KEX
fprintf(stderr, "key '%c'== ", c);
dump_digest("key", digest, need);
#endif
return digest;
}
void
ssh_hmac_free(struct ssh_hmac_ctx *ctx)
{
if (ctx != NULL) {
ssh_digest_free(ctx->ictx);
ssh_digest_free(ctx->octx);
ssh_digest_free(ctx->digest);
if (ctx->buf) {
explicit_bzero(ctx->buf, ctx->buf_len);
free(ctx->buf);
}
explicit_bzero(ctx, sizeof(*ctx));
free(ctx);
}
}
int
derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
u_int8_t cookie[8], u_int8_t id[16])
{
u_int8_t nbuf[2048], obuf[SSH_DIGEST_MAX_LENGTH];
struct ssh_digest_ctx *hashctx = NULL;
size_t len;
int r;
len = BN_num_bytes(host_modulus);
if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
return SSH_ERR_KEY_BITS_MISMATCH;
if (BN_bn2bin(host_modulus, nbuf) <= 0 ||
(hashctx = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
ssh_digest_update(hashctx, nbuf, len) != 0 ||
ssh_digest_update(hashctx, cookie, 8) != 0 ||
ssh_digest_final(hashctx, obuf, sizeof(obuf)) != 0) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
memcpy(id, obuf, ssh_digest_bytes(SSH_DIGEST_MD5));
r = 0;
out:
ssh_digest_free(hashctx);
explicit_bzero(nbuf, sizeof(nbuf));
explicit_bzero(obuf, sizeof(obuf));
return r;
}
int
ssh_digest_memory(int alg, const void *m, size_t mlen, u_char *d, size_t dlen)
{
struct ssh_digest_ctx *ctx = ssh_digest_start(alg);
if (ctx == NULL)
return SSH_ERR_INVALID_ARGUMENT;
if (ssh_digest_update(ctx, m, mlen) != 0 ||
ssh_digest_final(ctx, d, dlen) != 0)
return SSH_ERR_INVALID_ARGUMENT;
ssh_digest_free(ctx);
return 0;
}
struct ssh_digest_ctx *
ssh_digest_start(int alg)
{
const struct ssh_digest *digest = ssh_digest_by_alg(alg);
struct ssh_digest_ctx *ret;
if (digest == NULL || ((ret = calloc(1, sizeof(*ret))) == NULL))
return NULL;
ret->alg = alg;
if ((ret->mdctx = EVP_MD_CTX_new()) == NULL) {
free(ret);
return NULL;
}
if (EVP_DigestInit_ex(ret->mdctx, digest->mdfunc(), NULL) != 1) {
ssh_digest_free(ret);
return NULL;
}
return ret;
}
/*
* Computes the proper response to a RSA challenge, and sends the response to
* the server.
*/
static void
respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
{
u_char buf[32], response[16];
struct ssh_digest_ctx *md;
int i, len;
/* Decrypt the challenge using the private key. */
/* XXX think about Bleichenbacher, too */
if (rsa_private_decrypt(challenge, challenge, prv) != 0)
packet_disconnect(
"respond_to_rsa_challenge: rsa_private_decrypt failed");
/* Compute the response. */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || (u_int)len > sizeof(buf))
packet_disconnect(
"respond_to_rsa_challenge: bad challenge length %d", len);
memset(buf, 0, sizeof(buf));
BN_bn2bin(challenge, buf + sizeof(buf) - len);
if ((md = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
ssh_digest_update(md, buf, 32) < 0 ||
ssh_digest_update(md, session_id, 16) < 0 ||
ssh_digest_final(md, response, sizeof(response)) < 0)
fatal("%s: md5 failed", __func__);
ssh_digest_free(md);
debug("Sending response to host key RSA challenge.");
/* Send the response back to the server. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(response[i]);
packet_send();
packet_write_wait();
explicit_bzero(buf, sizeof(buf));
explicit_bzero(response, sizeof(response));
explicit_bzero(&md, sizeof(md));
}
static int
derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
const u_char *shared_secret, u_int slen, u_char **keyp)
{
struct kex *kex = ssh->kex;
struct sshbuf *b = NULL;
struct ssh_digest_ctx *hashctx = NULL;
char c = id;
u_int have;
size_t mdsz;
u_char *digest;
int r;
if ((mdsz = ssh_digest_bytes(kex->hash_alg)) == 0)
return SSH_ERR_INVALID_ARGUMENT;
if ((digest = calloc(1, roundup(need, mdsz))) == NULL ||
(b = sshbuf_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = sshbuf_put(b, shared_secret, slen)) < 0)
goto out;
/* K1 = HASH(K || H || "A" || session_id) */
if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
ssh_digest_update_buffer(hashctx, b) != 0 ||
ssh_digest_update(hashctx, hash, hashlen) != 0 ||
ssh_digest_update(hashctx, &c, 1) != 0 ||
ssh_digest_update(hashctx, kex->session_id,
kex->session_id_len) != 0 ||
ssh_digest_final(hashctx, digest, mdsz) != 0) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
ssh_digest_free(hashctx);
hashctx = NULL;
/*
* expand key:
* Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
* Key = K1 || K2 || ... || Kn
*/
for (have = mdsz; need > have; have += mdsz) {
if ((hashctx = ssh_digest_start(kex->hash_alg)) == NULL ||
ssh_digest_update_buffer(hashctx, b) != 0 ||
ssh_digest_update(hashctx, hash, hashlen) != 0 ||
ssh_digest_update(hashctx, digest, have) != 0 ||
ssh_digest_final(hashctx, digest + have, mdsz) != 0) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
ssh_digest_free(hashctx);
hashctx = NULL;
}
#ifdef DEBUG_KEX
fprintf(stderr, "key '%c'== ", c);
dump_digest("key", digest, need);
#endif
*keyp = digest;
digest = NULL;
r = 0;
out:
if (digest)
free(digest);
if (b)
sshbuf_free(b);
ssh_digest_free(hashctx);
return r;
}
