From ee45a34907ffeb5fd95b0513040d8491d565b663 Mon Sep 17 00:00:00 2001
From: Eldar Zaitov <[email protected]>
Date: Wed, 30 Jan 2013 23:22:27 +0100
Subject: [PATCH] Curl_sasl_create_digest_md5_message: fix buffer overflow

When negotiating SASL DIGEST-MD5 authentication, the function
Curl_sasl_create_digest_md5_message() uses the data provided from the
server without doing the proper length checks and that data is then
appended to a local fixed-size buffer on the stack.

This vulnerability can be exploited by someone who is in control of a
server that a libcurl based program is accessing with POP3, SMTP or
IMAP. For applications that accept user provided URLs, it is also
thinkable that a malicious user would feed an application with a URL to
a server hosting code targetting this flaw.

Bug: http://curl.haxx.se/docs/adv_20130206.html

(Note that these changes need to be applied to similar code in 
 .../lib/smtp.c for curl version 7.26.0)

--- lib/smtp.c.orig	2013-02-05 08:06:03.823585006 -0800
+++ lib/smtp.c	2013-02-05 08:12:38.007595100 -0800
@@ -879,7 +879,7 @@
   char cnonce[]     = "12345678"; /* will be changed */
   char method[]     = "AUTHENTICATE";
   char qop[]        = "auth";
-  char uri[128]     = "smtp/";
+  char uri[128];
   char response[512];
 
   (void)instate; /* no use for this yet */
@@ -963,8 +963,8 @@
   for(i = 0; i < MD5_DIGEST_LEN; i++)
     snprintf(&HA1_hex[2 * i], 3, "%02x", digest[i]);
 
-  /* Orepare URL string, append realm to the protocol */
-  strcat(uri, realm);
+  /* Prepare URL string, append realm to the protocol */
+  snprintf(uri, sizeof(uri), "smtp/%s", realm);
 
   /* Calculate H(A2) */
   ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
@@ -1008,20 +1008,11 @@
   for(i = 0; i < MD5_DIGEST_LEN; i++)
     snprintf(&resp_hash_hex[2 * i], 3, "%02x", digest[i]);
 
-  strcpy(response, "username=\"");
-  strcat(response, conn->user);
-  strcat(response, "\",realm=\"");
-  strcat(response, realm);
-  strcat(response, "\",nonce=\"");
-  strcat(response, nonce);
-  strcat(response, "\",cnonce=\"");
-  strcat(response, cnonce);
-  strcat(response, "\",nc=");
-  strcat(response, nonceCount);
-  strcat(response, ",digest-uri=\"");
-  strcat(response, uri);
-  strcat(response, "\",response=");
-  strcat(response, resp_hash_hex);
+  snprintf(response, sizeof(response),
+           "username=\"%s\",realm=\"%s\",nonce=\"%s\","
+           "cnonce=\"%s\",nc=\"%s\",digest-uri=\"%s\",response=%s",
+           conn->user, realm, nonce,
+           cnonce, nonceCount, uri, resp_hash_hex);
 
   /* Encode it to base64 and send it */
   result = Curl_base64_encode(data, response, 0, &rplyb64, &len);