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From ee45a34907ffeb5fd95b0513040d8491d565b663 Mon Sep 17 00:00:00 2001
From: Eldar Zaitov <kyprizel@volema.com>
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
---
lib/curl_sasl.c | 23 ++++++-----------------
1 file changed, 6 insertions(+), 17 deletions(-)
diff --git a/lib/curl_sasl.c b/lib/curl_sasl.c
index 57116b6..d07387d 100644
--- a/lib/curl_sasl.c
+++ b/lib/curl_sasl.c
@@ -346,9 +346,7 @@ CURLcode Curl_sasl_create_digest_md5_message(struct SessionHandle *data,
snprintf(&HA1_hex[2 * i], 3, "%02x", digest[i]);
/* Prepare the URL string */
- strcpy(uri, service);
- strcat(uri, "/");
- strcat(uri, realm);
+ snprintf(uri, sizeof(uri), "%s/%s", service, realm);
/* Calculate H(A2) */
ctxt = Curl_MD5_init(Curl_DIGEST_MD5);
@@ -392,20 +390,11 @@ CURLcode Curl_sasl_create_digest_md5_message(struct SessionHandle *data,
for(i = 0; i < MD5_DIGEST_LEN; i++)
snprintf(&resp_hash_hex[2 * i], 3, "%02x", digest[i]);
- strcpy(response, "username=\"");
- strcat(response, userp);
- 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",
+ userp, realm, nonce,
+ cnonce, nonceCount, uri, resp_hash_hex);
/* Base64 encode the reply */
return Curl_base64_encode(data, response, 0, outptr, outlen);
--
1.7.10.4
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