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curl/lib/escape.c
Daniel Stenberg 75ca568fa1 URL sanitize: reject URLs containing bad data
Protocols (IMAP, POP3 and SMTP) that use the path part of a URL in a
decoded manner now use the new Curl_urldecode() function to reject URLs
with embedded control codes (anything that is or decodes to a byte value
less than 32).

URLs containing such codes could easily otherwise be used to do harm and
allow users to do unintended actions with otherwise innocent tools and
applications. Like for example using a URL like
pop3://pop3.example.com/1%0d%0aDELE%201 when the app wants a URL to get
a mail and instead this would delete one.

This flaw is considered a security vulnerability: CVE-2012-0036

Security advisory at: http://curl.haxx.se/docs/adv_20120124.html

Reported by: Dan Fandrich
2012-01-24 08:54:26 +01:00

234 lines
6.4 KiB
C

/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at http://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
***************************************************************************/
/* Escape and unescape URL encoding in strings. The functions return a new
* allocated string or NULL if an error occurred. */
#include "setup.h"
#include <curl/curl.h>
#include "curl_memory.h"
#include "urldata.h"
#include "warnless.h"
#include "non-ascii.h"
#include "escape.h"
#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>
/* The last #include file should be: */
#include "memdebug.h"
/* Portable character check (remember EBCDIC). Do not use isalnum() because
its behavior is altered by the current locale.
See http://tools.ietf.org/html/rfc3986#section-2.3
*/
static bool Curl_isunreserved(unsigned char in)
{
switch (in) {
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case 'a': case 'b': case 'c': case 'd': case 'e':
case 'f': case 'g': case 'h': case 'i': case 'j':
case 'k': case 'l': case 'm': case 'n': case 'o':
case 'p': case 'q': case 'r': case 's': case 't':
case 'u': case 'v': case 'w': case 'x': case 'y': case 'z':
case 'A': case 'B': case 'C': case 'D': case 'E':
case 'F': case 'G': case 'H': case 'I': case 'J':
case 'K': case 'L': case 'M': case 'N': case 'O':
case 'P': case 'Q': case 'R': case 'S': case 'T':
case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z':
case '-': case '.': case '_': case '~':
return TRUE;
default:
break;
}
return FALSE;
}
/* for ABI-compatibility with previous versions */
char *curl_escape(const char *string, int inlength)
{
return curl_easy_escape(NULL, string, inlength);
}
/* for ABI-compatibility with previous versions */
char *curl_unescape(const char *string, int length)
{
return curl_easy_unescape(NULL, string, length, NULL);
}
char *curl_easy_escape(CURL *handle, const char *string, int inlength)
{
size_t alloc = (inlength?(size_t)inlength:strlen(string))+1;
char *ns;
char *testing_ptr = NULL;
unsigned char in; /* we need to treat the characters unsigned */
size_t newlen = alloc;
size_t strindex=0;
size_t length;
CURLcode res;
ns = malloc(alloc);
if(!ns)
return NULL;
length = alloc-1;
while(length--) {
in = *string;
if(Curl_isunreserved(in))
/* just copy this */
ns[strindex++]=in;
else {
/* encode it */
newlen += 2; /* the size grows with two, since this'll become a %XX */
if(newlen > alloc) {
alloc *= 2;
testing_ptr = realloc(ns, alloc);
if(!testing_ptr) {
free( ns );
return NULL;
}
else {
ns = testing_ptr;
}
}
res = Curl_convert_to_network(handle, &in, 1);
if(res) {
/* Curl_convert_to_network calls failf if unsuccessful */
free(ns);
return NULL;
}
snprintf(&ns[strindex], 4, "%%%02X", in);
strindex+=3;
}
string++;
}
ns[strindex]=0; /* terminate it */
return ns;
}
/*
* Curl_urldecode() URL decodes the given string.
*
* Optionally detects control characters (byte codes lower than 32) in the
* data and rejects such data.
*
* Returns a pointer to a malloced string in *ostring with length given in
* *olen. If length == 0, the length is assumed to be strlen(string).
*
*/
CURLcode Curl_urldecode(struct SessionHandle *data,
const char *string, size_t length,
char **ostring, size_t *olen,
bool reject_ctrl)
{
size_t alloc = (length?length:strlen(string))+1;
char *ns = malloc(alloc);
unsigned char in;
size_t strindex=0;
unsigned long hex;
CURLcode res;
if(!ns)
return CURLE_OUT_OF_MEMORY;
while(--alloc > 0) {
in = *string;
if(('%' == in) && ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
/* this is two hexadecimal digits following a '%' */
char hexstr[3];
char *ptr;
hexstr[0] = string[1];
hexstr[1] = string[2];
hexstr[2] = 0;
hex = strtoul(hexstr, &ptr, 16);
in = curlx_ultouc(hex); /* this long is never bigger than 255 anyway */
res = Curl_convert_from_network(data, &in, 1);
if(res) {
/* Curl_convert_from_network calls failf if unsuccessful */
free(ns);
return res;
}
string+=2;
alloc-=2;
}
if(reject_ctrl && (in < 0x20)) {
free(ns);
return CURLE_URL_MALFORMAT;
}
ns[strindex++] = in;
string++;
}
ns[strindex]=0; /* terminate it */
if(olen)
/* store output size */
*olen = strindex;
if(ostring)
/* store output string */
*ostring = ns;
return CURLE_OK;
}
/*
* Unescapes the given URL escaped string of given length. Returns a
* pointer to a malloced string with length given in *olen.
* If length == 0, the length is assumed to be strlen(string).
* If olen == NULL, no output length is stored.
*/
char *curl_easy_unescape(CURL *handle, const char *string, int length,
int *olen)
{
char *str = NULL;
size_t inputlen = length;
size_t outputlen;
CURLcode res = Curl_urldecode(handle, string, inputlen, &str, &outputlen,
FALSE);
if(res)
return NULL;
if(olen)
*olen = curlx_uztosi(outputlen);
return str;
}
/* For operating systems/environments that use different malloc/free
systems for the app and for this library, we provide a free that uses
the library's memory system */
void curl_free(void *p)
{
if(p)
free(p);
}