From 404d6a18006346cbc32b82dca3f74d3e99ed5c1e Mon Sep 17 00:00:00 2001
From: Emil Lerch <emil@lerch.org>
Date: Thu, 6 Jan 2022 14:34:45 -0800
Subject: [PATCH] fix memory corruption

---
 src/crypt.zig | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/crypt.zig b/src/crypt.zig
index 3ef5095..33661fb 100644
--- a/src/crypt.zig
+++ b/src/crypt.zig
@@ -53,18 +53,20 @@ pub fn encryptWithKey(allocator: std.mem.Allocator, key: [key_size]u8, data: []u
 
     // deal with final block, PKCS#7 padding
     {
-        in = @ptrCast(*[block_size]u8, data[(total_blocks * block_size)..]);
+        // We can't just ptrcast into data as we are likely to run over the end
+        // of the data memory. We'll declare a new input buffer
+        var in_last: [block_size]u8 = undefined;
         const padding: u8 = @intCast(u8, block_size - (data.len % block_size));
         var inx: u8 = 0;
         for (data[(total_blocks * block_size)..]) |b| {
-            in[inx] = b;
+            in_last[inx] = b;
             inx += 1;
         }
         while (inx < out.len) {
-            in[inx] = padding;
+            in_last[inx] = padding;
             inx += 1;
         }
-        ctx.encrypt(out[0..], in[0..]);
+        ctx.encrypt(out[0..], in_last[0..]);
         encrypted.appendSliceAssumeCapacity(out[0..]);
     }
     return encrypted.toOwnedSlice();