Re: BUG #16476: pgp_sym_encrypt_bytea with compress-level=6 :Wrong key or corrupt data

At Wed, 3 Jun 2020 08:35:02 -0400, Jeff Janes <jeff.janes@gmail.com> wrote in 
> I can reproduce this at any compression level if the data is random (not
> compressible) and exactly 16365 bytes long.  If the data is compressible,
> then you need a longer length of message to reproduce it and it depends on
> the random content and compression level.
> 
> I'm attaching the reproducer as a Perl script.  I have not investigated the
> C code of pgcrypto itself.

Thanks for the reproducer.

Compressed stream must end with a normal packet. If a stream ends with
a complete stream packet, deflator adds a zero-length normal packet at
the end.  decompress_read forgets to read such a terminating packet
when EOF comes at just at the end of the last stream packet. An extra
call to pullf_read at EOF correctly consumes such an extra packet.
The extra call doesn't harm if a stream ends with partial normal
packet.

The reproducer becomes not to fail with the attached patch.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center
From f4a8997ec08c0aaec8326b0f0dda9f3a001d5865 Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horikyoga.ntt@gmail.com>
Date: Thu, 11 Jun 2020 20:29:23 +0900
Subject: [PATCH] Make sure to consume stream-terminating packet

When compressed stream is ended with a full stream packet, it must be
followed by a terminating normal packet with zero-length.  Make sure
consume such terminating packet at the end of stream.
---
 contrib/pgcrypto/pgp-compress.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/contrib/pgcrypto/pgp-compress.c b/contrib/pgcrypto/pgp-compress.c
index 0505bdee92..69a8d6c577 100644
--- a/contrib/pgcrypto/pgp-compress.c
+++ b/contrib/pgcrypto/pgp-compress.c
@@ -286,7 +286,20 @@ restart:
 
     dec->buf_data = dec->buf_len - dec->stream.avail_out;
     if (res == Z_STREAM_END)
+    {
+        uint8 *tmp;
+
+        /*
+         * If source stream ends with a full stream packet, it is followed by
+         * an extra normal zero-length packet, which should be consumed before
+         * reading further. If we have already seen a terminating packet,
+         * nothing happen by this call.
+         */
+        res = pullf_read(src, 1, &tmp);
+        Assert(res == 0);
+        
         dec->eof = 1;
+    }
     goto restart;
 }
 
-- 
2.18.2