From 052cf082b0faaef4eaaa4e94119d7a1437aac4a3 Mon Sep 17 00:00:00 2001
From: squidadm <squidadm@users.noreply.github.com>
Date: Wed, 18 Oct 2023 04:50:56 +1300
Subject: [PATCH] Fix stack buffer overflow when parsing Digest Authorization
 (#1517)

The bug was discovered and detailed by Joshua Rogers at
https://megamansec.github.io/Squid-Security-Audit/digest-overflow.html
where it was filed as "Stack Buffer Overflow in Digest Authentication".

---------

Co-authored-by: Alex Bason <nonsleepr@gmail.com>
Co-authored-by: Amos Jeffries <yadij@users.noreply.github.com>

Conflict:NA
Reference:http://www.squid-cache.org/Versions/v5/SQUID-2023_3.patch
---
 src/auth/digest/Config.cc | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/auth/digest/Config.cc b/src/auth/digest/Config.cc
index d42831a55..be9f3c433 100644
--- a/src/auth/digest/Config.cc
+++ b/src/auth/digest/Config.cc
@@ -844,11 +844,15 @@ Auth::Digest::Config::decode(char const *proxy_auth, const HttpRequest *request,
             break;
 
         case DIGEST_NC:
-            if (value.size() != 8) {
+            if (value.size() == 8) {
+                // for historical reasons, the nc value MUST be exactly 8 bytes
+                static_assert(sizeof(digest_request->nc) == 8 + 1, "bad nc buffer size");
+                xstrncpy(digest_request->nc, value.rawBuf(), value.size() + 1);
+                debugs(29, 9, "Found noncecount '" << digest_request->nc << "'");
+            } else {
                 debugs(29, 9, "Invalid nc '" << value << "' in '" << temp << "'");
+                digest_request->nc[0] = 0;
             }
-            xstrncpy(digest_request->nc, value.rawBuf(), value.size() + 1);
-            debugs(29, 9, "Found noncecount '" << digest_request->nc << "'");
             break;
 
         case DIGEST_CNONCE:
-- 
2.25.1


