From 2ac3020bb680458361779135d4eb54d40d8adc5f Mon Sep 17 00:00:00 2001
From: Paul Adelsbach <paul.adelsbach@wolfssl.com>
Date: Mon, 30 Mar 2026 15:02:13 -0700
Subject: [PATCH] Add buffer size and callback checks to external
 wc_LmsKey_Sign

---
 wolfcrypt/src/ext_lms.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/wolfcrypt/src/ext_lms.c b/wolfcrypt/src/ext_lms.c
index e45083c046..cd35423203 100644
--- a/wolfcrypt/src/ext_lms.c
+++ b/wolfcrypt/src/ext_lms.c
@@ -840,6 +840,22 @@ int wc_LmsKey_Sign(LmsKey* key, byte * sig, word32 * sigSz, const byte * msg,
         return -1;
     }
 
+    if ((size_t)*sigSz < len) {
+        /* Signature buffer too small. */
+        WOLFSSL_MSG("error: LMS sig buffer too small");
+        return BUFFER_E;
+    }
+
+    if (key->write_private_key == NULL) {
+        WOLFSSL_MSG("error: LmsKey write/read callbacks are not set");
+        return BAD_FUNC_ARG;
+    }
+
+    if (key->context == NULL) {
+        WOLFSSL_MSG("error: LmsKey context is not set");
+        return BAD_FUNC_ARG;
+    }
+
     result = hss_generate_signature(key->working_key, LmsWritePrivKey,
                                     key, (const void *) msg, msgSz,
                                     sig, len, &key->info);