From 3064ce6bfa8669f86c58ed74fb3f737671ec7fb1 Mon Sep 17 00:00:00 2001
From: Keuin <keuinx@gmail.com>
Date: Sat, 28 May 2022 01:26:32 +0800
Subject: Bugfix: buggy pkcs7 unpad implementation. SEGV when n=1.

---
 main.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/main.c b/main.c
index 97dac06..37f5a0a 100644
--- a/main.c
+++ b/main.c
@@ -117,6 +117,10 @@ bool yield_possible_key(
  * the data is not padded with valid pkcs7 */
 int pkcs7_check_pad(const char *buf, size_t n) {
     if (!n) return -1;
+    if (n == 1) {
+        /* if total length is 1, the only valid string is 0x1 */
+        return (buf[0] == 1u) ? 1 : -1;
+    }
     --n;
     unsigned char pad = buf[n--];
     if (!pad) return -1;
-- 
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