[meta-lts-collab][kirkstone][PATCH 5/7] strongswan: Fix CVE-2026-35332

From: Nitin Wankhade <[email protected]>

Upstream-Status: Backport [https://snapshot.debian.org/archive/debian-security-debug/20260422T125423Z/pool/updates/main/s/strongswan/strongswan_6.0.1-6%2Bdeb13u5.debian.tar.xz]

Signed-off-by: Nitin Wankhade <[email protected]>
---
 ...accept-non-empty-ECDH-public-keys-wi.patch | 51 +++++++++++++++++++
 .../strongswan/strongswan_5.9.13.bbappend     |  1 +
 2 files changed, 52 insertions(+)
 create mode 100644 meta-networking/recipes-support/strongswan/files/tls-server-Only-accept-non-empty-ECDH-public-keys-wi.patch

diff --git a/meta-networking/recipes-support/strongswan/files/tls-server-Only-accept-non-empty-ECDH-public-keys-wi.patch b/meta-networking/recipes-support/strongswan/files/tls-server-Only-accept-non-empty-ECDH-public-keys-wi.patch
new file mode 100644
index 0000000..a46479f
--- /dev/null
+++ b/meta-networking/recipes-support/strongswan/files/tls-server-Only-accept-non-empty-ECDH-public-keys-wi.patch
@@ -0,0 +1,51 @@
+From: Tobias Brunner <[email protected]>
+Date: Fri, 20 Mar 2026 17:38:07 +0100
+Subject: tls-server: Only accept non-empty ECDH public keys with TLS < 1.3
+
+This prevents a crash due to a null-pointer dereference when processing
+an empty ECDH public key.
+
+The previous length check only applied in the `!ec` case, so in the `ec`
+case, the access to `pub.ptr[0]` was unguarded.  If a crafted TLS
+record ends with an empty ClientKeyExchange, then `read_data8` sets
+`pub` to `chunk_empty`, causing a null-pointer dereference.
+
+Note that if some data follows the empty ClientKeyExchange, this just
+causes a 1-byte out-of-bounds read that has no further effect as the
+TLS session is aborted immediately.  Either because the read value
+doesn't equal TLS_ANSI_UNCOMPRESSED or because the empty public key
+is rejected by `set_public_key()`.
+
+The referenced commit that introduced the pointer access, added the
+check for `pub.len` specifically to the `!ec` case, while the pointer
+access was initially unconditional (probably because the code was just
+copied from `tls_peer.c` which processes ECDH public keys in a separate
+function, so there was no `ec` flag).  The latter was fixed a couple of
+days later with 7b3c01845f63 ("Read the compression type byte for EC
+groups, only").  However, that commit didn't change the length check.
+Anyway, it's possible that the original intention was to add the check
+to the `ec` case on the previous line, or that there was some confusion
+with the parenthesis and something like the current code was intended to
+begin with.
+
+Fixes: e6cce7ff0d1b ("Prepend point format to ECDH public key")
+Fixes: CVE-2026-35332
+
+CVE: CVE-2026-35332
+Upstream-Status: Backport [https://snapshot.debian.org/archive/debian-security-debug/20260422T125423Z/pool/updates/main/s/strongswan/strongswan_6.0.1-6%2Bdeb13u5.debian.tar.xz]
+Patch is refreshed as per the source code version 5.9.13
+Signed-off-by: Nitin Wankhade <[email protected]>
+===
+diff --git a/src/libtls/tls_server.c b/src/libtls/tls_server.c
+index 7b2238e..bffc01c 100644
+--- a/src/libtls/tls_server.c
++++ b/src/libtls/tls_server.c
+@@ -857,7 +857,7 @@ static status_t process_key_exchange_dhe(private_tls_server_t *this,
+ 	group = this->dh->get_method(this->dh);
+ 	ec = key_exchange_is_ecdh(group);
+ 	if ((ec && !reader->read_data8(reader, &pub)) ||
+-		(!ec && (!reader->read_data16(reader, &pub) || pub.len == 0)))
++		(!ec && !reader->read_data16(reader, &pub)) || pub.len == 0)
+ 	{
+ 		DBG1(DBG_TLS, "received invalid Client Key Exchange");
+ 		this->alert->add(this->alert, TLS_FATAL, TLS_DECODE_ERROR);
diff --git a/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend b/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend
index 5b30348..8ccb230 100644
--- a/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend
+++ b/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend
@@ -3,4 +3,5 @@ SRC_URI += "\
     file://pkcs5-pkcs7-Avoid-NULL-pointer-dereference-when-veri.patch \
     file://libsimaka-Reject-zero-length-EAP-SIM-AKA-attributes.patch \
     file://constraints-Case-insensitive-matching-and-reject-exc.patch \
+    file://tls-server-Only-accept-non-empty-ECDH-public-keys-wi.patch \
 "
-- 
2.34.1