87 lines
3.9 KiB
Diff
87 lines
3.9 KiB
Diff
From 45b6522eb80a6d12f75630fe1c132b52fc3f1624 Mon Sep 17 00:00:00 2001
|
|
From: Thomas Leroy <32497783+p4zuu@users.noreply.github.com>
|
|
Date: Tue, 28 Nov 2023 07:35:46 +0000
|
|
Subject: [PATCH] Limit the number of allowed X-Forwarded-For hops (#1589)
|
|
|
|
Squid will ignore all X-Forwarded-For elements listed after the first 64
|
|
addresses allowed by the follow_x_forwarded_for directive. A different
|
|
limit can be specified by defining a C++ SQUID_X_FORWARDED_FOR_HOP_MAX
|
|
macro, but that macro is not a supported Squid configuration interface
|
|
and may change or disappear at any time.
|
|
|
|
Squid will log a cache.log ERROR if the hop limit has been reached.
|
|
|
|
This change works around problematic ACLChecklist and/or slow ACLs
|
|
implementation that results in immediate nonBlockingCheck() callbacks.
|
|
Such callbacks have caused many bugs and development complications. In
|
|
clientFollowXForwardedForCheck() context, they lead to indirect
|
|
recursion that was bound only by the number of allowed XFF entries,
|
|
which could reach thousands and exhaust Squid process call stack.
|
|
|
|
This recursion bug was discovered and detailed by Joshua Rogers at
|
|
https://megamansec.github.io/Squid-Security-Audit/xff-stackoverflow.html
|
|
where it was filed as "X-Forwarded-For Stack Overflow".
|
|
|
|
Conflict: NA
|
|
Reference: https://github.com/squid-cache/squid/commit/45b6522eb80a6d12f75630fe1c132b52fc3f1624
|
|
---
|
|
src/ClientRequestContext.h | 7 ++++++-
|
|
src/client_side_request.cc | 17 +++++++++++++++--
|
|
2 files changed, 21 insertions(+), 3 deletions(-)
|
|
|
|
diff --git a/src/ClientRequestContext.h b/src/ClientRequestContext.h
|
|
index 16c33bba4bc..0997f5d22b6 100644
|
|
--- a/src/ClientRequestContext.h
|
|
+++ b/src/ClientRequestContext.h
|
|
@@ -80,8 +80,13 @@ class ClientRequestContext : public RefCountable
|
|
#if USE_OPENSSL
|
|
bool sslBumpCheckDone = false;
|
|
#endif
|
|
- ErrorState *error = nullptr; ///< saved error page for centralized/delayed processing
|
|
+
|
|
bool readNextRequest = false; ///< whether Squid should read after error handling
|
|
+ ErrorState *error = nullptr; ///< saved error page for centralized/delayed processing
|
|
+
|
|
+#if FOLLOW_X_FORWARDED_FOR
|
|
+ size_t currentXffHopNumber = 0; ///< number of X-Forwarded-For header values processed so far
|
|
+#endif
|
|
};
|
|
|
|
#endif /* SQUID_CLIENTREQUESTCONTEXT_H */
|
|
diff --git a/src/client_side_request.cc b/src/client_side_request.cc
|
|
index 5b5b5af8086..7f802d4219e 100644
|
|
--- a/src/client_side_request.cc
|
|
+++ b/src/client_side_request.cc
|
|
@@ -75,6 +75,11 @@
|
|
#endif
|
|
|
|
#if FOLLOW_X_FORWARDED_FOR
|
|
+
|
|
+#if !defined(SQUID_X_FORWARDED_FOR_HOP_MAX)
|
|
+#define SQUID_X_FORWARDED_FOR_HOP_MAX 64
|
|
+#endif
|
|
+
|
|
static void clientFollowXForwardedForCheck(Acl::Answer answer, void *data);
|
|
#endif /* FOLLOW_X_FORWARDED_FOR */
|
|
|
|
@@ -437,8 +442,16 @@ clientFollowXForwardedForCheck(Acl::Answer answer, void *data)
|
|
/* override the default src_addr tested if we have to go deeper than one level into XFF */
|
|
Filled(calloutContext->acl_checklist)->src_addr = request->indirect_client_addr;
|
|
}
|
|
- calloutContext->acl_checklist->nonBlockingCheck(clientFollowXForwardedForCheck, data);
|
|
- return;
|
|
+ if (++calloutContext->currentXffHopNumber < SQUID_X_FORWARDED_FOR_HOP_MAX) {
|
|
+ calloutContext->acl_checklist->nonBlockingCheck(clientFollowXForwardedForCheck, data);
|
|
+ return;
|
|
+ }
|
|
+ const auto headerName = Http::HeaderLookupTable.lookup(Http::HdrType::X_FORWARDED_FOR).name;
|
|
+ debugs(28, DBG_CRITICAL, "ERROR: Ignoring trailing " << headerName << " addresses" <<
|
|
+ Debug::Extra << "addresses allowed by follow_x_forwarded_for: " << calloutContext->currentXffHopNumber <<
|
|
+ Debug::Extra << "last/accepted address: " << request->indirect_client_addr <<
|
|
+ Debug::Extra << "ignored trailing addresses: " << request->x_forwarded_for_iterator);
|
|
+ // fall through to resume clientAccessCheck() processing
|
|
}
|
|
}
|
|
|
|
--
|