options: Add option to set server accepted pubkey types

The added option SSH_BIND_OPTIONS_PUBKEY_ACCEPTED_KEY_TYPES allows
restricting the allowed public key types accepted by the server for
authentication.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/src/bind.c b/src/bind.c
index a1f25de2..d5193f77 100644
--- a/src/bind.c
+++ b/src/bind.c
@@ -38,6 +38,7 @@
 #include "libssh/buffer.h"
 #include "libssh/socket.h"
 #include "libssh/session.h"
+#include "libssh/token.h"
 
 /**
  * @addtogroup libssh_server
@@ -402,6 +403,7 @@ void ssh_bind_free(ssh_bind sshbind){
   SAFE_FREE(sshbind->banner);
   SAFE_FREE(sshbind->bindaddr);
   SAFE_FREE(sshbind->config_dir);
+  SAFE_FREE(sshbind->pubkey_accepted_key_types);
 
   SAFE_FREE(sshbind->dsakey);
   SAFE_FREE(sshbind->rsakey);
@@ -456,6 +458,29 @@ int ssh_bind_accept_fd(ssh_bind sshbind, ssh_session session, socket_t fd){
       }
     }
 
+    if (sshbind->pubkey_accepted_key_types != NULL) {
+        if (session->opts.pubkey_accepted_types == NULL) {
+            session->opts.pubkey_accepted_types = strdup(sshbind->pubkey_accepted_key_types);
+            if (session->opts.pubkey_accepted_types == NULL) {
+                ssh_set_error_oom(sshbind);
+                return SSH_ERROR;
+            }
+        } else {
+            char *p;
+            /* If something was set to the session prior to calling this
+             * function, keep only what is allowed by the options set in
+             * sshbind */
+            p = ssh_find_all_matching(sshbind->pubkey_accepted_key_types,
+                                      session->opts.pubkey_accepted_types);
+            if (p == NULL) {
+                return SSH_ERROR;
+            }
+
+            SAFE_FREE(session->opts.pubkey_accepted_types);
+            session->opts.pubkey_accepted_types = p;
+        }
+    }
+
     session->common.log_verbosity = sshbind->common.log_verbosity;
     if(sshbind->banner != NULL)
     	session->opts.custombanner = strdup(sshbind->banner);