Revert "kex: server fix for first_kex_packet_follows"

The patch breaks the client with ECDSA.

This reverts commit 5865b9436fda96ac9fc7c18e4dffe5fb12dcc515.

1 files changed, 64 insertions, 149 deletions

diff --git a/src/kex.c b/src/kex.c
index c5dd2130..4eb45d22 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -275,172 +275,87 @@ char *ssh_find_matching(const char *available_d, const char *preferred_d){
     return NULL;
 }
 
-/**
- * @internal
- * @brief returns whether the first client key exchange algorithm matches
- *        the first server key exchange algorithm
- * @returns whether the first client key exchange algorithm matches
- *          the first server key exchange algorithm
- */
-static int is_first_kex_packet_follows_guess_wrong(const char *client_kex,
-                                                   const char *server_kex) {
-    int is_wrong = 1;
-    char **server_kex_tokens = NULL;
-    char **client_kex_tokens = tokenize(client_kex);
-
-    if (client_kex_tokens == NULL) {
-        goto out;
-    }
-
-    if (client_kex_tokens[0] == NULL) {
-        goto freeout;
-    }
-
-    server_kex_tokens = tokenize(server_kex);
-    if (server_kex_tokens == NULL) {
-        goto freeout;
-    }
-
-    is_wrong = (strcmp(client_kex_tokens[0], server_kex_tokens[0]) != 0);
-
-    SAFE_FREE(server_kex_tokens[0]);
-    SAFE_FREE(server_kex_tokens);
-freeout:
-    SAFE_FREE(client_kex_tokens[0]);
-    SAFE_FREE(client_kex_tokens);
-out:
-    return is_wrong;
-}
-
 SSH_PACKET_CALLBACK(ssh_packet_kexinit){
-    int i;
-    int server_kex=session->server;
-    ssh_string str = NULL;
-    char *strings[KEX_METHODS_SIZE];
-    int rc = SSH_ERROR;
-
-    uint8_t first_kex_packet_follows = 0;
-    uint32_t kexinit_reserved = 0;
-
-    (void)type;
-    (void)user;
-
-    memset(strings, 0, sizeof(strings));
-    if (session->session_state == SSH_SESSION_STATE_AUTHENTICATED){
-        SSH_LOG(SSH_LOG_WARNING, "Other side initiating key re-exchange");
-    } else if(session->session_state != SSH_SESSION_STATE_INITIAL_KEX){
-        ssh_set_error(session,SSH_FATAL,"SSH_KEXINIT received in wrong state");
-        goto error;
-    }
-
-    if (server_kex) {
-        rc = buffer_get_data(packet,session->next_crypto->client_kex.cookie, 16);
-        if (rc != 16) {
-            ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: no cookie in packet");
-            goto error;
-        }
-
-        rc = hashbufin_add_cookie(session, session->next_crypto->client_kex.cookie);
-        if (rc < 0) {
-            ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: adding cookie failed");
-            goto error;
-        }
-    } else {
-        rc = buffer_get_data(packet,session->next_crypto->server_kex.cookie, 16);
-        if (rc != 16) {
-            ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: no cookie in packet");
-            goto error;
-        }
-
-        rc = hashbufin_add_cookie(session, session->next_crypto->server_kex.cookie);
-        if (rc < 0) {
-            ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: adding cookie failed");
-            goto error;
-        }
-    }
+	int server_kex=session->server;
+  ssh_string str = NULL;
+  char *strings[KEX_METHODS_SIZE];
+  int i;
 
-    for (i = 0; i < KEX_METHODS_SIZE; i++) {
-        str = buffer_get_ssh_string(packet);
-        if (str == NULL) {
-          break;
-        }
+  (void)type;
+  (void)user;
+  memset(strings, 0, sizeof(strings));
+  if (session->session_state == SSH_SESSION_STATE_AUTHENTICATED){
+      SSH_LOG(SSH_LOG_WARNING, "Other side initiating key re-exchange");
+  } else if(session->session_state != SSH_SESSION_STATE_INITIAL_KEX){
+  	ssh_set_error(session,SSH_FATAL,"SSH_KEXINIT received in wrong state");
+  	goto error;
+  }
+  if (server_kex) {
+      if (buffer_get_data(packet,session->next_crypto->client_kex.cookie,16) != 16) {
+        ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: no cookie in packet");
+        goto error;
+      }
 
-        rc = buffer_add_ssh_string(session->in_hashbuf, str);
-        if (rc < 0) {
-            ssh_set_error(session, SSH_FATAL, "Error adding string in hash buffer");
-            goto error;
-        }
+      if (hashbufin_add_cookie(session, session->next_crypto->client_kex.cookie) < 0) {
+        ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: adding cookie failed");
+        goto error;
+      }
+  } else {
+      if (buffer_get_data(packet,session->next_crypto->server_kex.cookie,16) != 16) {
+        ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: no cookie in packet");
+        goto error;
+      }
 
-        strings[i] = ssh_string_to_char(str);
-        if (strings[i] == NULL) {
-            ssh_set_error_oom(session);
-            goto error;
-        }
-        ssh_string_free(str);
-        str = NULL;
-    }
+      if (hashbufin_add_cookie(session, session->next_crypto->server_kex.cookie) < 0) {
+        ssh_set_error(session, SSH_FATAL, "ssh_packet_kexinit: adding cookie failed");
+        goto error;
+      }
+  }
 
-    /* copy the server kex info into an array of strings */
-    if (server_kex) {
-        for (i = 0; i < SSH_KEX_METHODS; i++) {
-            session->next_crypto->client_kex.methods[i] = strings[i];
-        }
-    } else { /* client */
-        for (i = 0; i < SSH_KEX_METHODS; i++) {
-            session->next_crypto->server_kex.methods[i] = strings[i];
-        }
+  for (i = 0; i < KEX_METHODS_SIZE; i++) {
+    str = buffer_get_ssh_string(packet);
+    if (str == NULL) {
+      break;
     }
 
-    /*
-     * Handle the two final fields for the KEXINIT message (RFC 4253 7.1):
-     *
-     *      boolean      first_kex_packet_follows
-     *      uint32       0 (reserved for future extension)
-     *
-     * Notably if clients set 'first_kex_packet_follows', it is expected
-     * that its value is included when computing the session ID (see
-     * 'make_sessionid').
-     */
-    rc = buffer_get_u8(packet, &first_kex_packet_follows);
-    if (rc != 1) {
-        goto error;
+    if (buffer_add_ssh_string(session->in_hashbuf, str) < 0) {
+    	ssh_set_error(session, SSH_FATAL, "Error adding string in hash buffer");
+      goto error;
     }
 
-    rc = buffer_add_u8(session->in_hashbuf, first_kex_packet_follows);
-    if (rc < 0) {
-        goto error;
+    strings[i] = ssh_string_to_char(str);
+    if (strings[i] == NULL) {
+    	ssh_set_error_oom(session);
+      goto error;
     }
+    ssh_string_free(str);
+    str = NULL;
+  }
 
-    rc = buffer_add_u32(session->in_hashbuf, kexinit_reserved);
-    if (rc < 0) {
-        goto error;
+  /* copy the server kex info into an array of strings */
+  if (server_kex) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
+      session->next_crypto->client_kex.methods[i] = strings[i];
     }
-
-    /*
-     * Remember whether 'first_kex_packet_follows' was set and the client
-     * guess was wrong: in this case the next SSH_MSG_KEXDH_INIT message
-     * must be ignored.
-     */
-    if (server_kex && first_kex_packet_follows) {
-      session->first_kex_follows_guess_wrong =
-        is_first_kex_packet_follows_guess_wrong(session->next_crypto->client_kex.methods[SSH_KEX],
-                                                session->next_crypto->server_kex.methods[SSH_KEX]);
+  } else { /* client */
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
+      session->next_crypto->server_kex.methods[i] = strings[i];
     }
+  }
 
-    session->session_state = SSH_SESSION_STATE_KEXINIT_RECEIVED;
-    session->dh_handshake_state = DH_STATE_INIT;
-    session->ssh_connection_callback(session);
-    return SSH_PACKET_USED;
-
+  session->session_state=SSH_SESSION_STATE_KEXINIT_RECEIVED;
+  session->dh_handshake_state=DH_STATE_INIT;
+  session->ssh_connection_callback(session);
+  return SSH_PACKET_USED;
 error:
-    ssh_string_free(str);
-    for (i = 0; i < SSH_KEX_METHODS; i++) {
-        SAFE_FREE(strings[i]);
-    }
+  ssh_string_free(str);
+  for (i = 0; i < SSH_KEX_METHODS; i++) {
+    SAFE_FREE(strings[i]);
+  }
 
-    session->session_state = SSH_SESSION_STATE_ERROR;
+  session->session_state = SSH_SESSION_STATE_ERROR;
 
-    return SSH_PACKET_USED;
+  return SSH_PACKET_USED;
 }
 
 void ssh_list_kex(struct ssh_kex_struct *kex) {