Use only one variable denoting the size of methods arrays

Previously, there was non-consistent usage of constans SSH_KEX_METHODS,
KEX_METHODS_SIZE and of magic number 10 to reference the arrays used
for algorithm negotiation by peers. This commit settles down to the single
constant and its usage throughout the whole codebase.

Fixes T195

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

include/libssh/bind.h

@@ -22,6 +22,7 @@
 #define BIND_H_
 
 #include "libssh/priv.h"
+#include "libssh/kex.h"
 #include "libssh/session.h"
 
 struct ssh_bind_struct {
@@ -31,7 +32,7 @@ struct ssh_bind_struct {
 
   struct ssh_poll_handle_struct *poll;
   /* options */
-  char *wanted_methods[10];
+  char *wanted_methods[SSH_KEX_METHODS];
   char *banner;
   char *ecdsakey;
   char *dsakey;

include/libssh/session.h

@@ -213,7 +213,7 @@ struct ssh_session_struct {
         char *sshdir;
         char *knownhosts;
         char *global_knownhosts;
-        char *wanted_methods[10];
+        char *wanted_methods[SSH_KEX_METHODS];
         char *pubkey_accepted_types;
         char *ProxyCommand;
         char *custombanner;

src/bind.c

@@ -411,7 +411,7 @@ void ssh_bind_free(ssh_bind sshbind){
   ssh_key_free(sshbind->ed25519);
   sshbind->ed25519 = NULL;
 
-  for (i = 0; i < 10; i++) {
+  for (i = 0; i < SSH_KEX_METHODS; i++) {
     if (sshbind->wanted_methods[i]) {
       SAFE_FREE(sshbind->wanted_methods[i]);
     }
@@ -442,7 +442,7 @@ int ssh_bind_accept_fd(ssh_bind sshbind, ssh_session session, socket_t fd){
     session->server = 1;
 
     /* Copy options from bind to session */
-    for (i = 0; i < 10; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
       if (sshbind->wanted_methods[i]) {
         session->opts.wanted_methods[i] = strdup(sshbind->wanted_methods[i]);
         if (session->opts.wanted_methods[i] == NULL) {

src/kex.c

@@ -159,8 +159,6 @@
     GEX_SHA1 \
     KEY_EXCHANGE
 
-#define KEX_METHODS_SIZE 10
-
 /* RFC 8308 */
 #define KEX_EXTENSION_CLIENT "ext-info-c"
 
@@ -257,7 +255,7 @@ static const char *ssh_kex_descriptions[] = {
 
 const char *ssh_kex_get_default_methods(uint32_t algo)
 {
-    if (algo >= KEX_METHODS_SIZE) {
+    if (algo >= SSH_KEX_METHODS) {
         return NULL;
     }
 
@@ -266,7 +264,7 @@ const char *ssh_kex_get_default_methods(uint32_t algo)
 
 const char *ssh_kex_get_supported_method(uint32_t algo)
 {
-    if (algo >= KEX_METHODS_SIZE) {
+    if (algo >= SSH_KEX_METHODS) {
         return NULL;
     }
 
@@ -274,7 +272,7 @@ const char *ssh_kex_get_supported_method(uint32_t algo)
 }
 
 const char *ssh_kex_get_description(uint32_t algo) {
-  if (algo >= KEX_METHODS_SIZE) {
+  if (algo >= SSH_KEX_METHODS) {
     return NULL;
   }
 
@@ -282,7 +280,7 @@ const char *ssh_kex_get_description(uint32_t algo) {
 }
 
 const char *ssh_kex_get_fips_methods(uint32_t algo) {
-  if (algo >= KEX_METHODS_SIZE) {
+  if (algo >= SSH_KEX_METHODS) {
     return NULL;
   }
 
@@ -333,7 +331,7 @@ SSH_PACKET_CALLBACK(ssh_packet_kexinit)
     int i, ok;
     int server_kex = session->server;
     ssh_string str = NULL;
-    char *strings[KEX_METHODS_SIZE] = {0};
+    char *strings[SSH_KEX_METHODS] = {0};
     char *rsa_sig_ext = NULL;
     int rc = SSH_ERROR;
 
@@ -376,7 +374,7 @@ SSH_PACKET_CALLBACK(ssh_packet_kexinit)
         }
     }
 
-    for (i = 0; i < KEX_METHODS_SIZE; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         str = ssh_buffer_get_ssh_string(packet);
         if (str == NULL) {
           goto error;
@@ -677,11 +675,11 @@ int ssh_set_client_kex(ssh_session session)
         return SSH_ERROR;
     }
 
-    memset(client->methods, 0, KEX_METHODS_SIZE * sizeof(char **));
+    memset(client->methods, 0, SSH_KEX_METHODS * sizeof(char **));
 
     /* Set the list of allowed algorithms in order of preference, if it hadn't
      * been set yet. */
-    for (i = 0; i < KEX_METHODS_SIZE; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         if (i == SSH_HOSTKEYS) {
             /* Set the hostkeys in the following order:
              * - First: keys present in known_hosts files ordered by preference
@@ -750,7 +748,7 @@ int ssh_kex_select_methods (ssh_session session){
         ext_start[0] = '\0';
     }
 
-    for (i = 0; i < KEX_METHODS_SIZE; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         session->next_crypto->kex_methods[i]=ssh_find_matching(server->methods[i],client->methods[i]);
         if(session->next_crypto->kex_methods[i] == NULL && i < SSH_LANG_C_S){
             ssh_set_error(session,SSH_FATAL,"kex error : no match for method %s: server [%s], client [%s]",
@@ -823,7 +821,7 @@ int ssh_send_kex(ssh_session session, int server_kex) {
 
   ssh_list_kex(kex);
 
-  for (i = 0; i < KEX_METHODS_SIZE; i++) {
+  for (i = 0; i < SSH_KEX_METHODS; i++) {
     str = ssh_string_from_char(kex->methods[i]);
     if (str == NULL) {
       goto error;

src/options.c

@@ -154,7 +154,7 @@ int ssh_options_copy(ssh_session src, ssh_session *dest)
         }
     }
 
-    for (i = 0; i < 10; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         if (src->opts.wanted_methods[i] != NULL) {
             new->opts.wanted_methods[i] = strdup(src->opts.wanted_methods[i]);
             if (new->opts.wanted_methods[i] == NULL) {

src/server.c

@@ -166,7 +166,7 @@ int server_set_kex(ssh_session session)
         return -1;
     }
 
-    for (i = 0; i < 10; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         wanted = session->opts.wanted_methods[i];
         if (wanted  == NULL) {
             if (ssh_fips_mode()) {
@@ -195,7 +195,7 @@ int ssh_server_init_kex(ssh_session session) {
     }
 
     /* free any currently-set methods: server_set_kex will allocate new ones */
-    for (i = 0; i < 10 /* SSH_KEX_METHODS */; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         SAFE_FREE(session->next_crypto->server_kex.methods[i]);
     }
 

src/session.c

@@ -314,7 +314,7 @@ void ssh_free(ssh_session session)
   SAFE_FREE(session->opts.gss_client_identity);
   SAFE_FREE(session->opts.pubkey_accepted_types);
 
-  for (i = 0; i < 10; i++) {
+  for (i = 0; i < SSH_KEX_METHODS; i++) {
       if (session->opts.wanted_methods[i]) {
           SAFE_FREE(session->opts.wanted_methods[i]);
       }

tests/unittests/torture_options.c

@@ -876,7 +876,7 @@ static void torture_options_copy(void **state)
     assert_string_equal(session->opts.knownhosts, new->opts.knownhosts);
     assert_string_equal(session->opts.global_knownhosts,
                         new->opts.global_knownhosts);
-    for (i = 0; i < 10; i++) {
+    for (i = 0; i < SSH_KEX_METHODS; i++) {
         if (session->opts.wanted_methods[i] == NULL) {
             assert_null(new->opts.wanted_methods[i]);
         } else {