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GUAC-1172: Simplify filename validation and manipulation.

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This commit is contained in:
Michael Jumper 2015-06-20 17:31:36 -07:00
parent 6bfd3e46e0
commit 482b3a728c
1 changed files with 66 additions and 45 deletions
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111
src/protocols/ssh/sftp.c
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@ -36,7 +36,29 @@
#include <guacamole/socket.h>
#include <guacamole/stream.h>
static bool __ssh_guac_valid_filename(char* filename) {
/**
* Concatenates the given filename with the given path, separating the two
* with a single forward slash. The full result must be no more than
* GUAC_SFTP_MAX_PATH bytes long, counting null terminator.
*
* @param fullpath
* The buffer to store the result within. This buffer must be at least
* GUAC_SFTP_MAX_PATH bytes long.
*
* @param path
* The path to append the filename to.
*
* @param filename
* The filename to appaned to the path.
*
* @return
* true if the filename is valid and was successfully appended to the path,
* false otherwise.
*/
static bool guac_ssh_append_filename(char* fullpath, const char* path,
const char* filename) {
int i;
/* Disallow "." as a filename */
if (strcmp(filename, ".") == 0)
@ -46,20 +68,51 @@ static bool __ssh_guac_valid_filename(char* filename) {
if (strcmp(filename, "..") == 0)
return false;
/* Search for path separator characters */
for (;;) {
/* Copy path, append trailing slash */
for (i=0; i<GUAC_SFTP_MAX_PATH; i++) {
/*
* Append trailing slash only if:
* 1) Trailing slash is not already present
* 2) Path is non-empty
*/
char c = path[i];
if (c == '\0') {
if (i > 0 && path[i-1] != '/')
fullpath[i++] = '/';
break;
}
/* Copy character if not end of string */
fullpath[i] = c;
}
/* Append filename */
for (; i<GUAC_SFTP_MAX_PATH; i++) {
char c = *(filename++);
if (c == '\0')
break;
/* Replace slashes with underscores */
/* Filenames may not contain slashes */
if (c == '\\' || c == '/')
return false;
/* Append each character within filename */
fullpath[i] = c;
}
/* If filename does not contain a path, it's ok */
/* Verify path length is within maximum */
if (i == GUAC_SFTP_MAX_PATH)
return false;
/* Terminate path string */
fullpath[i] = '\0';
/* Append was successful */
return true;
}
@ -70,56 +123,24 @@ int guac_sftp_file_handler(guac_client* client, guac_stream* stream,
ssh_guac_client_data* client_data = (ssh_guac_client_data*) client->data;
char fullpath[GUAC_SFTP_MAX_PATH];
LIBSSH2_SFTP_HANDLE* file;
int i;
/* Ensure filename is a valid filename and not a path */
if (!__ssh_guac_valid_filename(filename)) {
/* Concatenate filename with path */
if (!guac_ssh_append_filename(fullpath,
client_data->sftp_upload_path, filename)) {
guac_client_log(client, GUAC_LOG_DEBUG,
"Filename \"%s\" is invalid",
"Filename \"%s/%s\" is invalid or resulting path is too long",
filename);
guac_protocol_send_ack(client->socket, stream, "SFTP: Illegal filename",
/* Abort transfer - invalid filename */
guac_protocol_send_ack(client->socket, stream,
"SFTP: Illegal filename",
GUAC_PROTOCOL_STATUS_CLIENT_BAD_REQUEST);
guac_socket_flush(client->socket);
return 0;
}
/* Copy upload path, append trailing slash */
for (i=0; i<GUAC_SFTP_MAX_PATH; i++) {
char c = client_data->sftp_upload_path[i];
if (c == '\0') {
fullpath[i++] = '/';
break;
}
fullpath[i] = c;
}
/* Append filename */
for (; i<GUAC_SFTP_MAX_PATH; i++) {
char c = *(filename++);
if (c == '\0')
break;
fullpath[i] = c;
}
/* If path + filename exceeds max length, abort */
if (i == GUAC_SFTP_MAX_PATH) {
guac_client_log(client, GUAC_LOG_DEBUG,
"Filename exceeds maximum of %i characters",
GUAC_SFTP_MAX_PATH);
guac_protocol_send_ack(client->socket, stream, "SFTP: Name too long", GUAC_PROTOCOL_STATUS_CLIENT_OVERRUN);
guac_socket_flush(client->socket);
return 0;
}
/* Terminate path string */
fullpath[i] = '\0';
/* Open file via SFTP */
file = libssh2_sftp_open(client_data->sftp_session, fullpath,
LIBSSH2_FXF_WRITE | LIBSSH2_FXF_CREAT | LIBSSH2_FXF_TRUNC,