GUACAMOLE-269: Merge support for overriding the character sequence sent for backspace for SSH/telnet.

src/protocols/ssh/Makefile.am

@@ -29,6 +29,7 @@ libguac_client_ssh_la_SOURCES = \
     settings.c                  \
     sftp.c                      \
     ssh.c                       \
+    ttymode.c                   \
     user.c
 
 noinst_HEADERS =                \
@@ -38,6 +39,7 @@ noinst_HEADERS =                \
     settings.h                  \
     sftp.h                      \
     ssh.h                       \
+    ttymode.h                   \
     user.h
 
 # Add agent sources if enabled

src/protocols/ssh/settings.c

@@ -56,6 +56,7 @@ const char* GUAC_SSH_CLIENT_ARGS[] = {
     "create-recording-path",
     "read-only",
     "server-alive-interval",
+    "backspace",
     NULL
 };
 
@@ -209,6 +210,13 @@ enum SSH_ARGS_IDX {
      */
     IDX_SERVER_ALIVE_INTERVAL,
 
+    /**
+     * The ASCII code, as an integer, to send for the backspace key, as configured
+     * by the SSH connection from the client.  By default this will be 127,
+     * the ASCII DELETE code.
+     */
+    IDX_BACKSPACE,
+
     SSH_ARGS_COUNT
 };
 
@@ -348,6 +356,11 @@ guac_ssh_settings* guac_ssh_parse_args(guac_user* user,
         guac_user_parse_args_int(user, GUAC_SSH_CLIENT_ARGS, argv,
                 IDX_SERVER_ALIVE_INTERVAL, 0);
 
+    /* Parse backspace key setting */
+    settings->backspace =
+        guac_user_parse_args_int(user, GUAC_SSH_CLIENT_ARGS, argv,
+                IDX_BACKSPACE, 127);
+
     /* Parsing was successful */
     return settings;
 

src/protocols/ssh/settings.h

@@ -223,6 +223,11 @@ typedef struct guac_ssh_settings {
      */
     int server_alive_interval;
 
+    /**
+     * The integer ASCII code of the command to send for backspace.
+     */
+    int backspace;
+
 } guac_ssh_settings;
 
 /**

src/protocols/ssh/ssh.c

@@ -26,6 +26,7 @@
 #include "sftp.h"
 #include "ssh.h"
 #include "terminal/terminal.h"
+#include "ttymode.h"
 
 #ifdef ENABLE_SSH_AGENT
 #include "ssh_agent.h"
@@ -191,6 +192,8 @@ void* ssh_client_thread(void* data) {
         return NULL;
     }
 
+    char ssh_ttymodes[GUAC_SSH_TTYMODES_SIZE(1)];
+
     /* Set up screen recording, if requested */
     if (settings->recording_path != NULL) {
         ssh_client->recording = guac_common_recording_create(client,
@@ -206,7 +209,7 @@ void* ssh_client_thread(void* data) {
     ssh_client->term = guac_terminal_create(client,
             settings->font_name, settings->font_size,
             settings->resolution, settings->width, settings->height,
-            settings->color_scheme);
+            settings->color_scheme, settings->backspace);
 
     /* Fail if terminal init failed */
     if (ssh_client->term == NULL) {
@@ -296,9 +299,17 @@ void* ssh_client_thread(void* data) {
 
     }
 
+    /* Set up the ttymode array prior to requesting the PTY */
+    int ttymodeBytes = guac_ssh_ttymodes_init(ssh_ttymodes,
+            GUAC_SSH_TTY_OP_VERASE, settings->backspace, GUAC_SSH_TTY_OP_END);
+    if (ttymodeBytes < 1)
+        guac_client_log(client, GUAC_LOG_WARNING, "Unable to set TTY modes."
+                "  Backspace may not work as expected.");
+
     /* Request PTY */
-    if (libssh2_channel_request_pty_ex(ssh_client->term_channel, "linux", sizeof("linux")-1, NULL, 0,
+    if (libssh2_channel_request_pty_ex(ssh_client->term_channel, "linux", sizeof("linux")-1,
-            ssh_client->term->term_width, ssh_client->term->term_height, 0, 0)) {
+            ssh_ttymodes, ttymodeBytes, ssh_client->term->term_width,
+            ssh_client->term->term_height, 0, 0)) {
         guac_client_abort(client, GUAC_PROTOCOL_STATUS_UPSTREAM_ERROR, "Unable to allocate PTY.");
         return NULL;
     }

src/protocols/ssh/ttymode.c

@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#include "config.h"
+#include "ttymode.h"
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+int guac_ssh_ttymodes_init(char opcode_array[], ...) {
+
+    /* Initialize the variable argument list. */
+    va_list args;
+    va_start(args, opcode_array);
+
+    /* Initialize array pointer and byte counter. */
+    char *current = opcode_array;
+
+    /* Loop through variable argument list. */
+    while (true) {
+       
+        /* Next argument should be an opcode. */
+        char opcode = (char)va_arg(args, int);
+        *(current++) = opcode;
+
+        /* If it's the end opcode, we're done. */
+        if (opcode == GUAC_SSH_TTY_OP_END)
+            break;
+
+        /* Next argument should be 4-byte value. */
+        uint32_t value = va_arg(args, uint32_t);
+        *(current++) = (value >> 24) & 0xFF;
+        *(current++) = (value >> 16) & 0xFF;
+        *(current++) = (value >> 8) & 0xFF;
+        *(current++) = value & 0xFF;
+    }
+
+    /* We're done processing arguments. */
+    va_end(args);
+
+    return current - opcode_array;
+
+}

src/protocols/ssh/ttymode.h

@@ -0,0 +1,89 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef GUAC_SSH_TTYMODE_H
+#define GUAC_SSH_TTYMODE_H
+
+#include "config.h"
+
+#include <stdint.h>
+
+/**
+ * The size of a TTY mode encoding opcode and
+ * value pair.  As defined in the SSH RFC, this
+ * is 5 bytes - a single byte for the opcode, and
+ * 4 bytes for the value.
+ */
+#define GUAC_SSH_TTY_OPCODE_SIZE 5
+
+/**
+ * The SSH TTY mode encoding opcode that terminates
+ * the list of TTY modes.
+ */
+#define GUAC_SSH_TTY_OP_END 0
+
+/**
+ * The SSH TTY mode encoding opcode that configures
+ * the TTY erase code to configure the server
+ * backspace key.
+ */
+#define GUAC_SSH_TTY_OP_VERASE 3
+
+/**
+ * Macro for calculating the number of bytes required
+ * to pass a given number of opcodes, which calculates
+ * the size of the number of opcodes plus the single byte
+ * end opcode.
+ *
+ * @param num_opcodes
+ *     The number of opcodes for which a size in bytes
+ *     should be calculated.
+ *
+ * @returns
+ *     The number of bytes that the given number of
+ *     opcodes will require.
+ */
+#define GUAC_SSH_TTYMODES_SIZE(num_opcodes) ((GUAC_SSH_TTY_OPCODE_SIZE * num_opcodes) + 1)
+
+/**
+ * Opcodes and value pairs are passed to the SSH connection
+ * in a single array, beginning with the opcode and followed
+ * by a four byte value, repeating until the end opcode is
+ * encountered.  This function takes the array that will be
+ * sent and a variable number of opcode and value pair
+ * arguments and places the opcode and values in the array
+ * as expected by the SSH connection.
+ *
+ * @param opcode_array
+ *     Pointer to the opcode array that will ultimately
+ *     be passed to the SSH connection.  The array must
+ *     be size to handle 5 bytes for each opcode and value
+ *     pair, plus one additional byte for the end opcode.
+ *
+ * @params ...
+ *     A variable number of opcode and value pairs
+ *     to place in the array.
+ *
+ * @return
+ *     Number of bytes written to the array, or zero
+ *     if a failure occurs.
+ */
+int guac_ssh_ttymodes_init(char opcode_array[], ...);
+
+#endif

src/protocols/telnet/settings.c

@@ -50,6 +50,7 @@ const char* GUAC_TELNET_CLIENT_ARGS[] = {
     "recording-include-keys",
     "create-recording-path",
     "read-only",
+    "backspace",
     NULL
 };
 
@@ -174,6 +175,12 @@ enum TELNET_ARGS_IDX {
      */
     IDX_READ_ONLY,
 
+    /**
+     * ASCII code, as an integer to use for the backspace key, or 127
+     * if not specified.
+     */
+    IDX_BACKSPACE,
+
     TELNET_ARGS_COUNT
 };
 
@@ -328,6 +335,11 @@ guac_telnet_settings* guac_telnet_parse_args(guac_user* user,
         guac_user_parse_args_boolean(user, GUAC_TELNET_CLIENT_ARGS, argv,
                 IDX_CREATE_RECORDING_PATH, false);
 
+    /* Parse backspace key code */
+    settings->backspace =
+        guac_user_parse_args_int(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                IDX_BACKSPACE, 127);
+
     /* Parsing was successful */
     return settings;
 

src/protocols/telnet/settings.h

@@ -207,6 +207,13 @@ typedef struct guac_telnet_settings {
      */
     bool recording_include_keys;
 
+    /**
+     * The ASCII code, as an integer, that the telnet client will use when the
+     * backspace key is pressed.  By default, this is 127, ASCII delete, if
+     * not specified in the client settings.
+     */
+    int backspace;
+
 } guac_telnet_settings;
 
 /**

src/protocols/telnet/telnet.c

@@ -480,7 +480,7 @@ void* guac_telnet_client_thread(void* data) {
     telnet_client->term = guac_terminal_create(client,
             settings->font_name, settings->font_size,
             settings->resolution, settings->width, settings->height,
-            settings->color_scheme);
+            settings->color_scheme, settings->backspace);
 
     /* Fail if terminal init failed */
     if (telnet_client->term == NULL) {

src/terminal/terminal.c

@@ -257,7 +257,8 @@ void* guac_terminal_thread(void* data) {
 
 guac_terminal* guac_terminal_create(guac_client* client,
         const char* font_name, int font_size, int dpi,
-        int width, int height, const char* color_scheme) {
+        int width, int height, const char* color_scheme,
+        const int backspace) {
 
     int default_foreground;
     int default_background;
@@ -406,6 +407,9 @@ guac_terminal* guac_terminal_create(guac_client* client,
         return NULL;
     }
 
+    /* Configure backspace */
+    term->backspace = backspace;
+
     return term;
 
 }
@@ -1594,7 +1598,11 @@ static int __guac_terminal_send_key(guac_terminal* term, int keysym, int pressed
         /* Non-printable keys */
         else {
 
-            if (keysym == 0xFF08) return guac_terminal_send_string(term, "\x7F"); /* Backspace */
+            /* Backspace can vary based on configuration of terminal by client. */
+            if (keysym == 0xFF08) {
+                char backspace_str[] = { term->backspace, '\0' };
+                return guac_terminal_send_string(term, backspace_str);
+            }
             if (keysym == 0xFF09 || keysym == 0xFF89) return guac_terminal_send_string(term, "\x09"); /* Tab */
             if (keysym == 0xFF0D || keysym == 0xFF8D) return guac_terminal_send_string(term, "\x0D"); /* Enter */
             if (keysym == 0xFF1B) return guac_terminal_send_string(term, "\x1B"); /* Esc */

src/terminal/terminal/terminal.h

@@ -432,6 +432,11 @@ struct guac_terminal {
      */
     guac_common_clipboard* clipboard;
 
+    /**
+     * ASCII character to send when backspace is pressed.
+     */
+    char backspace;
+
 };
 
 /**
@@ -464,13 +469,18 @@ struct guac_terminal {
  *     invalid, a warning will be logged, and the terminal will fall back on
  *     GUAC_TERMINAL_SCHEME_GRAY_BLACK.
  *
+ * @param backspace
+ *     The integer ASCII code to send when backspace is pressed in
+ *     this terminal.
+ *
  * @return
  *     A new guac_terminal having the given font, dimensions, and attributes
  *     which renders all text to the given client.
  */
 guac_terminal* guac_terminal_create(guac_client* client,
         const char* font_name, int font_size, int dpi,
-        int width, int height, const char* color_scheme);
+        int width, int height, const char* color_scheme,
+        const int backspace);
 
 /**
  * Frees all resources associated with the given terminal.