- BN_mask_bits(session_key_int, sizeof(session_key) * 8);
- len = BN_num_bytes(session_key_int);
- if (len < 0 || len > sizeof(session_key))
- fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
- get_remote_ipaddr(),
- len, sizeof(session_key));
- memset(session_key, 0, sizeof(session_key));
- BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
+ if (!rsafail) {
+ BN_mask_bits(session_key_int, sizeof(session_key) * 8);
+ len = BN_num_bytes(session_key_int);
+ if (len < 0 || len > sizeof(session_key)) {
+ error("do_connection: bad session key len from %s: "
+ "session_key_int %d > sizeof(session_key) %lu",
+ get_remote_ipaddr(), len, (u_long)sizeof(session_key));
+ rsafail++;
+ } else {
+ memset(session_key, 0, sizeof(session_key));
+ BN_bn2bin(session_key_int,
+ session_key + sizeof(session_key) - len);
+
+ compute_session_id(session_id, cookie,
+ sensitive_data.ssh1_host_key->rsa->n,
+ sensitive_data.server_key->rsa->n);
+ /*
+ * Xor the first 16 bytes of the session key with the
+ * session id.
+ */
+ for (i = 0; i < 16; i++)
+ session_key[i] ^= session_id[i];
+ }
+ }
+ if (rsafail) {
+ int bytes = BN_num_bytes(session_key_int);
+ char *buf = xmalloc(bytes);
+ MD5_CTX md;
+
+ log("do_connection: generating a fake encryption key");
+ BN_bn2bin(session_key_int, buf);
+ MD5_Init(&md);
+ MD5_Update(&md, buf, bytes);
+ MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
+ MD5_Final(session_key, &md);
+ MD5_Init(&md);
+ MD5_Update(&md, session_key, 16);
+ MD5_Update(&md, buf, bytes);
+ MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
+ MD5_Final(session_key + 16, &md);
+ memset(buf, 0, bytes);
+ xfree(buf);
+ for (i = 0; i < 16; i++)
+ session_id[i] = session_key[i] ^ session_key[i + 16];
+ }
+ /* Destroy the private and public keys. They will no longer be needed. */
+ destroy_sensitive_data();