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Fix corner case with PGP decompression in pgcrypto

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A compressed stream may end with an empty packet, and PGP decompression
finished before reading this empty packet in the remaining stream.  This
caused a failure in pgcrypto, handling this case as corrupted data.
This commit makes sure to consume such extra data, avoiding a failure
when decompression the entire stream.  This corner case was reproducible
with a data length of 16kB, and existed since its introduction in
e94dd6a.  A cheap regression test is added to cover this case.

Thanks to Jeff Janes for the extra investigation.

Reported-by: Frank Gagnepain
Author: Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/16476-692ef7b84e5fb893@postgresql.org
Backpatch-through: 9.5
This commit is contained in:
Michael Paquier 2020-07-22 14:52:23 +09:00
parent a5073871ea
commit 9e108984fb
3 changed files with 62 additions and 11 deletions
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30
contrib/pgcrypto/expected/pgp-compression.out
View File

@ -48,3 +48,33 @@ select pgp_sym_decrypt(
Secret message
(1 row)
-- check corner case involving an input string of 16kB, as per bug #16476.
SELECT setseed(0);
setseed
---------
(1 row)
WITH random_string AS
(
-- This generates a random string of 16366 bytes. This is chosen
-- as random so that it does not get compressed, and the decompression
-- would work on a string with the same length as the origin, making the
-- test behavior more predictible. lpad() ensures that the generated
-- hexadecimal value is completed by extra zero characters if random()
-- has generated a value strictly lower than 16.
SELECT string_agg(decode(lpad(to_hex((random()*256)::int), 2, '0'), 'hex'), '') as bytes
FROM generate_series(0, 16365)
)
SELECT bytes =
pgp_sym_decrypt_bytea(
pgp_sym_encrypt_bytea(bytes, 'key',
'compress-algo=1,compress-level=1'),
'key', 'expect-compress-algo=1')
AS is_same
FROM random_string;
is_same
---------
t
(1 row)

22
contrib/pgcrypto/pgp-compress.c
View File

@ -243,6 +243,17 @@ decompress_read(void *priv, PullFilter *src, int len,
struct DecomprData *dec = priv;
restart:
if (dec->stream.avail_in == 0)
{
uint8 *tmp;
res = pullf_read(src, 8192, &tmp);
if (res < 0)
return res;
dec->stream.next_in = tmp;
dec->stream.avail_in = res;
}
if (dec->buf_data > 0)
{
if (len > dec->buf_data)
@ -256,17 +267,6 @@ restart:
if (dec->eof)
return 0;
if (dec->stream.avail_in == 0)
{
uint8 *tmp;
res = pullf_read(src, 8192, &tmp);
if (res < 0)
return res;
dec->stream.next_in = tmp;
dec->stream.avail_in = res;
}
dec->stream.next_out = dec->buf;
dec->stream.avail_out = dec->buf_len;
dec->pos = dec->buf;

21
contrib/pgcrypto/sql/pgp-compression.sql
View File

@ -28,3 +28,24 @@ select pgp_sym_decrypt(
pgp_sym_encrypt('Secret message', 'key',
'compress-algo=2, compress-level=0'),
'key', 'expect-compress-algo=0');
-- check corner case involving an input string of 16kB, as per bug #16476.
SELECT setseed(0);
WITH random_string AS
(
-- This generates a random string of 16366 bytes. This is chosen
-- as random so that it does not get compressed, and the decompression
-- would work on a string with the same length as the origin, making the
-- test behavior more predictible. lpad() ensures that the generated
-- hexadecimal value is completed by extra zero characters if random()
-- has generated a value strictly lower than 16.
SELECT string_agg(decode(lpad(to_hex((random()*256)::int), 2, '0'), 'hex'), '') as bytes
FROM generate_series(0, 16365)
)
SELECT bytes =
pgp_sym_decrypt_bytea(
pgp_sym_encrypt_bytea(bytes, 'key',
'compress-algo=1,compress-level=1'),
'key', 'expect-compress-algo=1')
AS is_same
FROM random_string;