feat: add support for sftp extension "home-directory"

Signed-off-by: Debanga Sarma <deb737@proton.me>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

include/libssh/sftp.h

@@ -1144,6 +1144,27 @@ LIBSSH_API int sftp_server_version(sftp_session sftp);
  */
 LIBSSH_API char *sftp_expand_path(sftp_session sftp, const char *path);
 
+/**
+ * @brief Get the specified user's home directory
+ *
+ * This calls the "home-directory" extension. You should check if the extension
+ * is supported using:
+ *
+ * @code
+ * int supported  = sftp_extension_supported(sftp, "home-directory", "1");
+ * @endcode
+ *
+ * @param sftp          The sftp session handle.
+ *
+ * @param username      username of the user whose home directory is requested.
+ *
+ * @return              On success, a newly allocated string containing the
+ *                      absolute real-path of the home directory of the user.
+ *                      NULL on error. The caller needs to free the memory
+ *                      using ssh_string_free_char().
+ */
+LIBSSH_API char *sftp_home_directory(sftp_session sftp, const char *username);
+
 #ifdef WITH_SERVER
 /**
  * @brief Create a new sftp server session.

src/sftp.c

@@ -3100,4 +3100,93 @@ char *sftp_expand_path(sftp_session sftp, const char *path)
     return NULL;
 }
 
+char *
+sftp_home_directory(sftp_session sftp, const char *username)
+{
+    sftp_status_message status = NULL;
+    sftp_message msg = NULL;
+    ssh_buffer buffer = NULL;
+    uint32_t id;
+    int rc;
+
+    if (sftp == NULL) {
+        return NULL;
+    }
+
+    buffer = ssh_buffer_new();
+    if (buffer == NULL) {
+        ssh_set_error_oom(sftp->session);
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return NULL;
+    }
+
+    id = sftp_get_new_id(sftp);
+
+    rc = ssh_buffer_pack(buffer,
+                         "dss",
+                         id,
+                         "home-directory",
+                         username ? username : "");
+    if (rc != SSH_OK) {
+        ssh_set_error_oom(sftp->session);
+        SSH_BUFFER_FREE(buffer);
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return NULL;
+    }
+
+    rc = sftp_packet_write(sftp, SSH_FXP_EXTENDED, buffer);
+    SSH_BUFFER_FREE(buffer);
+    if (rc < 0) {
+        return NULL;
+    }
+
+    while (msg == NULL) {
+        rc = sftp_read_and_dispatch(sftp);
+        if (rc < 0) {
+            return NULL;
+        }
+        msg = sftp_dequeue(sftp, id);
+    }
+
+    if (msg->packet_type == SSH_FXP_NAME) {
+        uint32_t ignored = 0;
+        char *homepath = NULL;
+
+        rc = ssh_buffer_unpack(msg->payload, "ds", &ignored, &homepath);
+        sftp_message_free(msg);
+        if (rc != SSH_OK) {
+            ssh_set_error(sftp->session,
+                          SSH_ERROR,
+                          "Failed to query user home directory");
+            sftp_set_error(sftp, SSH_FX_FAILURE);
+            return NULL;
+        }
+
+        return homepath;
+    } else if (msg->packet_type == SSH_FXP_STATUS) {
+        status = parse_status_msg(msg);
+        sftp_message_free(msg);
+        if (status == NULL) {
+            return NULL;
+        }
+
+        sftp_set_error(sftp, status->status);
+        ssh_set_error(sftp->session,
+                      SSH_REQUEST_DENIED,
+                      "SFTP server: %s",
+                      status->errormsg);
+        status_msg_free(status);
+    } else {
+        ssh_set_error(
+            sftp->session,
+            SSH_FATAL,
+            "Received message %d when attempting to query user home directory",
+            msg->packet_type);
+        sftp_message_free(msg);
+        sftp_set_error(sftp, SSH_FX_BAD_MESSAGE);
+    }
+
+    return NULL;
+}
+
 #endif /* WITH_SFTP */