GUACAMOLE-547: Merge support for SSH NONE authentication method.

src/common-ssh/common-ssh/ssh.h

@@ -25,6 +25,23 @@
 #include <guacamole/client.h>
 #include <libssh2.h>
 
+/**
+ * Handler for retrieving additional credentials.
+ * 
+ * @param client
+ *     The Guacamole Client associated with this need for additional
+ *     credentials.
+ * 
+ * @param cred_name
+ *     The name of the credential being requested, which will be shared
+ *     with the client in order to generate a meaningful prompt.
+ * 
+ * @return
+ *     A newly-allocated string containing the credentials provided by
+ *     the user, which must be freed by a call to free().
+ */
+typedef char* guac_ssh_credential_handler(guac_client* client, char* cred_name);
+
 /**
  * An SSH session, backed by libssh2 and associated with a particular
  * Guacamole client.
@@ -50,6 +67,11 @@ typedef struct guac_common_ssh_session {
      * The file descriptor of the socket being used for the SSH connection.
      */
     int fd;
+    
+    /**
+     * Callback function to retrieve credentials.
+     */
+    guac_ssh_credential_handler* credential_handler;
 
 } guac_common_ssh_session;
 
@@ -92,14 +114,32 @@ void guac_common_ssh_uninit();
  *
  * @param user
  *     The user to authenticate as, once connected.
+ * 
+ * @param keepalive
+ *     How frequently the connection should send keepalive packets, in
+ *     seconds.  Zero disables keepalive packets, and 2 is the minimum
+ *     configurable value.
+ * 
+ * @param host_key
+ *     The known public host key of the server, as provided by the client.  If
+ *     provided the identity of the server will be checked against this key,
+ *     and a mis-match between this and the server identity will cause the
+ *     connection to fail.  If not provided, no checks will be done and the
+ *     connection will proceed.
+ * 
+ * @param credential_handler
+ *     The handler function for retrieving additional credentials from the user
+ *     as required by the SSH server, or NULL if the user will not be asked
+ *     for additional credentials.
  *
  * @return
  *     A new SSH session if the connection and authentication succeed, or NULL
  *     if the connection or authentication were not successful.
  */
 guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
-        const char* hostname, const char* port, guac_common_ssh_user* user, int keepalive,
+        const char* hostname, const char* port, guac_common_ssh_user* user,
-        const char* host_key);
+        int keepalive, const char* host_key,
+        guac_ssh_credential_handler* credential_handler);
 
 /**
  * Disconnects and destroys the given SSH session, freeing all associated

src/common-ssh/ssh.c

@@ -304,20 +304,26 @@ static int guac_common_ssh_authenticate(guac_common_ssh_session* common_session)
     LIBSSH2_SESSION* session = common_session->session;
 
     /* Get user credentials */
-    char* username = user->username;
-    char* password = user->password;
     guac_common_ssh_key* key = user->private_key;
 
     /* Validate username provided */
-    if (username == NULL) {
+    if (user->username == NULL) {
         guac_client_abort(client, GUAC_PROTOCOL_STATUS_CLIENT_UNAUTHORIZED,
                 "SSH authentication requires a username.");
         return 1;
     }
 
     /* Get list of supported authentication methods */
-    char* user_authlist = libssh2_userauth_list(session, username,
+    char* user_authlist = libssh2_userauth_list(session, user->username,
-            strlen(username));
+            strlen(user->username));
+
+    /* If auth list is NULL, then authentication has succeeded with NONE */
+    if (user_authlist == NULL) {
+        guac_client_log(client, GUAC_LOG_DEBUG,
+            "SSH NONE authentication succeeded.");
+        return 0;
+    }
+
     guac_client_log(client, GUAC_LOG_DEBUG,
             "Supported authentication methods: %s", user_authlist);
 
@@ -333,7 +339,7 @@ static int guac_common_ssh_authenticate(guac_common_ssh_session* common_session)
         }
 
         /* Attempt public key auth */
-        if (libssh2_userauth_publickey(session, username,
+        if (libssh2_userauth_publickey(session, user->username,
                     (unsigned char*) key->public_key, key->public_key_length,
                     guac_common_ssh_sign_callback, (void**) key)) {
 
@@ -352,14 +358,18 @@ static int guac_common_ssh_authenticate(guac_common_ssh_session* common_session)
 
     }
 
+    /* Attempt authentication with username + password. */
+    if (user->password == NULL && common_session->credential_handler)
+            user->password = common_session->credential_handler(client, "Password: ");
+    
     /* Authenticate with password, if provided */
-    else if (password != NULL) {
+    if (user->password != NULL) {
 
         /* Check if password auth is supported on the server */
         if (strstr(user_authlist, "password") != NULL) {
 
             /* Attempt password authentication */
-            if (libssh2_userauth_password(session, username, password)) {
+            if (libssh2_userauth_password(session, user->username, user->password)) {
 
                 /* Abort on failure */
                 char* error_message;
@@ -380,7 +390,7 @@ static int guac_common_ssh_authenticate(guac_common_ssh_session* common_session)
         if (strstr(user_authlist, "keyboard-interactive") != NULL) {
 
             /* Attempt keyboard-interactive auth using provided password */
-            if (libssh2_userauth_keyboard_interactive(session, username,
+            if (libssh2_userauth_keyboard_interactive(session, user->username,
                         &guac_common_ssh_kbd_callback)) {
 
                 /* Abort on failure */
@@ -415,8 +425,9 @@ static int guac_common_ssh_authenticate(guac_common_ssh_session* common_session)
 }
 
 guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
-        const char* hostname, const char* port, guac_common_ssh_user* user, int keepalive,
+        const char* hostname, const char* port, guac_common_ssh_user* user,
-        const char* host_key) {
+        int keepalive, const char* host_key,
+        guac_ssh_credential_handler* credential_handler) {
 
     int retval;
 
@@ -561,6 +572,7 @@ guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
     common_session->user = user;
     common_session->session = session;
     common_session->fd = fd;
+    common_session->credential_handler = credential_handler;
 
     /* Attempt authentication */
     if (guac_common_ssh_authenticate(common_session)) {

src/protocols/rdp/rdp.c

@@ -975,7 +975,7 @@ void* guac_rdp_client_thread(void* data) {
         rdp_client->sftp_session =
             guac_common_ssh_create_session(client, settings->sftp_hostname,
                     settings->sftp_port, rdp_client->sftp_user, settings->sftp_server_alive_interval,
-                    settings->sftp_host_key);
+                    settings->sftp_host_key, NULL);
 
         /* Fail if SSH connection does not succeed */
         if (rdp_client->sftp_session == NULL) {

src/protocols/ssh/ssh.c

@@ -130,19 +130,6 @@ static guac_common_ssh_user* guac_ssh_get_user(guac_client* client) {
 
     } /* end if key given */
 
-    /* Otherwise, use password */
-    else {
-
-        /* Get password if not provided */
-        if (settings->password == NULL)
-            settings->password = guac_terminal_prompt(ssh_client->term,
-                    "Password: ", false);
-
-        /* Set provided password */
-        guac_common_ssh_user_set_password(user, settings->password);
-
-    }
-
     /* Clear screen of any prompts */
     guac_terminal_printf(ssh_client->term, "\x1B[H\x1B[J");
 
@@ -150,6 +137,29 @@ static guac_common_ssh_user* guac_ssh_get_user(guac_client* client) {
 
 }
 
+/**
+ * A function used to generate a terminal prompt to gather additional
+ * credentials from the guac_client during a connection, and using
+ * the specified string to generate the prompt for the user.
+ * 
+ * @param client
+ *     The guac_client object associated with the current connection
+ *     where additional credentials are required.
+ * 
+ * @param cred_name
+ *     The prompt text to display to the screen when prompting for the
+ *     additional credentials.
+ * 
+ * @return 
+ *     The string of credentials gathered from the user.
+ */
+static char* guac_ssh_get_credential(guac_client *client, char* cred_name) {
+
+    guac_ssh_client* ssh_client = (guac_ssh_client*) client->data;
+    return guac_terminal_prompt(ssh_client->term, cred_name, false);
+    
+}
+
 void* ssh_input_thread(void* data) {
 
     guac_client* client = (guac_client*) data;
@@ -239,7 +249,7 @@ void* ssh_client_thread(void* data) {
     /* Open SSH session */
     ssh_client->session = guac_common_ssh_create_session(client,
             settings->hostname, settings->port, ssh_client->user, settings->server_alive_interval,
-            settings->host_key);
+            settings->host_key, guac_ssh_get_credential);
     if (ssh_client->session == NULL) {
         /* Already aborted within guac_common_ssh_create_session() */
         return NULL;
@@ -291,7 +301,7 @@ void* ssh_client_thread(void* data) {
         ssh_client->sftp_session =
             guac_common_ssh_create_session(client, settings->hostname,
                     settings->port, ssh_client->user, settings->server_alive_interval,
-                    settings->host_key);
+                    settings->host_key, NULL);
         if (ssh_client->sftp_session == NULL) {
             /* Already aborted within guac_common_ssh_create_session() */
             return NULL;

src/protocols/vnc/vnc.c

@@ -262,7 +262,7 @@ void* guac_vnc_client_thread(void* data) {
         vnc_client->sftp_session =
             guac_common_ssh_create_session(client, settings->sftp_hostname,
                     settings->sftp_port, vnc_client->sftp_user, settings->sftp_server_alive_interval,
-                    settings->sftp_host_key);
+                    settings->sftp_host_key, NULL);
 
         /* Fail if SSH connection does not succeed */
         if (vnc_client->sftp_session == NULL) {