- char *res = (char *)xmalloc (strlen (command)
- + (value ? (1 + strlen (value)) : 0)
- + 2 + 1);
- sprintf (res, "%s%s%s\r\n", command, value ? " " : "", value ? value : "");
+ char *res;
+ if (value)
+ {
+ /* Check for newlines in VALUE (possibly injected by the %0A URL
+ escape) making the callers inadvertently send multiple FTP
+ commands at once. Without this check an attacker could
+ intentionally redirect to ftp://server/fakedir%0Acommand.../
+ and execute arbitrary FTP command on a remote FTP server. */
+ if (strpbrk (value, "\r\n"))
+ {
+ /* Copy VALUE to the stack and modify CR/LF to space. */
+ char *defanged, *p;
+ STRDUP_ALLOCA (defanged, value);
+ for (p = defanged; *p; p++)
+ if (*p == '\r' || *p == '\n')
+ *p = ' ';
+ DEBUGP (("\nDetected newlines in %s \"%s\"; changing to %s \"%s\"\n",
+ command, escnonprint (value), command, escnonprint (defanged)));
+ /* Make VALUE point to the defanged copy of the string. */
+ value = defanged;
+ }
+ res = concat_strings (command, " ", value, "\r\n", (char *) 0);
+ }
+ else
+ res = concat_strings (command, "\r\n", (char *) 0);