From 40a42789d1cb1fb01f0c51bd9a222a0760ac9917 Mon Sep 17 00:00:00 2001
From: rsiddharth <s@ricketyspace.net>
Date: Sat, 28 Nov 2020 22:08:50 -0500
Subject: lib: blocks: add Pkcs7Padding

---
 lib/blocks.go | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'lib')

diff --git a/lib/blocks.go b/lib/blocks.go
index 9436d3c..1ba811f 100644
--- a/lib/blocks.go
+++ b/lib/blocks.go
@@ -60,3 +60,16 @@ func BlocksEqual(a, b []byte) bool {
 	}
 	return true
 }
+
+// Performs PKCS#7 Padding on the input `in` and block size `k`.
+// Assumes 0 > `k` < 256
+// Reference: https://tools.ietf.org/html/rfc5652#section-6.3
+func Pkcs7Padding(in []byte, k int) []byte {
+	lth := len(in)
+	pd := k - (lth % k) // padding character and padding length
+
+	for i := 0; i < pd; i++ {
+		in = append(in, byte(pd))
+	}
+	return in
+}
-- 
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