rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

pgcrypto: Report errant decryption as "Wrong key or corrupt data". 

This has been the predominant outcome.  When the output of decrypting
with a wrong key coincidentally resembled an OpenPGP packet header,
pgcrypto could instead report "Corrupt data", "Not text data" or
"Unsupported compression algorithm".  The distinct "Corrupt data"
message added no value.  The latter two error messages misled when the
decrypted payload also exhibited fundamental integrity problems.  Worse,
error message variance in other systems has enabled cryptologic attacks;
see RFC 4880 section "14. Security Considerations".  Whether these
pgcrypto behaviors are likewise exploitable is unknown.

In passing, document that pgcrypto does not resist side-channel attacks.
Back-patch to 9.0 (all supported versions).

Security: CVE-2015-3167
This commit is contained in:
Noah Misch 2015-05-18 10:02:31 -04:00
parent fd97bd411d
commit 85270ac7a2
9 changed files with 162 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
contrib/pgcrypto/expected/pgp-decrypt.out
View File

@ -372,3 +372,54 @@ select pgp_sym_decrypt(pgp_sym_encrypt(repeat('x',65530),'1'),'1') = repeat('x',
(1 row)
-- expected: true
-- Negative tests
-- Decryption with a certain incorrect key yields an apparent Literal Data
-- packet reporting its content to be binary data. Ciphertext source:
-- iterative pgp_sym_encrypt('secret', 'key') until the random prefix gave
-- rise to that property.
select pgp_sym_decrypt(dearmor('
-----BEGIN PGP MESSAGE-----
ww0EBwMCxf8PTrQBmJdl0jcB6y2joE7GSLKRv7trbNsF5Z8ou5NISLUg31llVH/S0B2wl4bvzZjV
VsxxqLSPzNLAeIspJk5G
=mSd/
-----END PGP MESSAGE-----
'), 'wrong-key', 'debug=1');
NOTICE: dbg: prefix_init: corrupt prefix
NOTICE: dbg: parse_literal_data: data type=b
NOTICE: dbg: mdcbuf_finish: bad MDC pkt hdr
ERROR: Wrong key or corrupt data
-- Routine text/binary mismatch.
select pgp_sym_decrypt(pgp_sym_encrypt_bytea('P', 'key'), 'key', 'debug=1');
NOTICE: dbg: parse_literal_data: data type=b
ERROR: Not text data
-- Decryption with a certain incorrect key yields an apparent BZip2-compressed
-- plaintext. Ciphertext source: iterative pgp_sym_encrypt('secret', 'key')
-- until the random prefix gave rise to that property.
select pgp_sym_decrypt(dearmor('
-----BEGIN PGP MESSAGE-----
ww0EBwMC9rK/dMkF5Zlt0jcBlzAQ1mQY2qYbKYbw8h3EZ5Jk0K2IiY92R82TRhWzBIF/8cmXDPtP
GXsd65oYJZp3Khz0qfyn
=Nmpq
-----END PGP MESSAGE-----
'), 'wrong-key', 'debug=1');
NOTICE: dbg: prefix_init: corrupt prefix
NOTICE: dbg: parse_compressed_data: bzip2 unsupported
NOTICE: dbg: mdcbuf_finish: bad MDC pkt hdr
ERROR: Wrong key or corrupt data
-- Routine use of BZip2 compression. Ciphertext source:
-- echo x | gpg --homedir /nonexistent --personal-compress-preferences bzip2 \
-- --personal-cipher-preferences aes --no-emit-version --batch \
-- --symmetric --passphrase key --armor
select pgp_sym_decrypt(dearmor('
-----BEGIN PGP MESSAGE-----
jA0EBwMCRhFrAKNcLVJg0mMBLJG1cCASNk/x/3dt1zJ+2eo7jHfjgg3N6wpB3XIe
QCwkWJwlBG5pzbO5gu7xuPQN+TbPJ7aQ2sLx3bAHhtYb0i3vV9RO10Gw++yUyd4R
UCAAw2JRIISttRHMfDpDuZJpvYo=
=AZ9M
-----END PGP MESSAGE-----
'), 'key', 'debug=1');
NOTICE: dbg: parse_compressed_data: bzip2 unsupported
ERROR: Unsupported compression algorithm

4
contrib/pgcrypto/expected/pgp-pubkey-decrypt.out
View File

@ -625,7 +625,7 @@ ERROR: No encryption key found
-- rsa: password-protected secret key, wrong password
select pgp_pub_decrypt(dearmor(data), dearmor(seckey), '123')
from keytbl, encdata where keytbl.id=7 and encdata.id=4;
ERROR: Corrupt data
ERROR: Wrong key or corrupt data
-- rsa: password-protected secret key, right password
select pgp_pub_decrypt(dearmor(data), dearmor(seckey), 'parool')
from keytbl, encdata where keytbl.id=7 and encdata.id=4;
@ -641,7 +641,7 @@ ERROR: Need password for secret key
-- password-protected secret key, wrong password
select pgp_pub_decrypt(dearmor(data), dearmor(seckey), 'foo')
from keytbl, encdata where keytbl.id=5 and encdata.id=1;
ERROR: Corrupt data
ERROR: Wrong key or corrupt data
-- password-protected secret key, right password
select pgp_pub_decrypt(dearmor(data), dearmor(seckey), 'parool')
from keytbl, encdata where keytbl.id=5 and encdata.id=1;

2
contrib/pgcrypto/mbuf.c
View File

@ -325,7 +325,7 @@ pullf_read_fixed(PullFilter *src, int len, uint8 *dst)
if (res != len)
{
px_debug("pullf_read_fixed: need=%d got=%d", len, res);
return PXE_MBUF_SHORT_READ;
return PXE_PGP_CORRUPT_DATA;
}
if (p != dst)
memcpy(dst, p, len);

70
contrib/pgcrypto/pgp-decrypt.c
View File

@ -236,6 +236,8 @@ pgp_create_pkt_reader(PullFilter **pf_p, PullFilter *src, int len,
/*
* Prefix check filter
* https://tools.ietf.org/html/rfc4880#section-5.7
* https://tools.ietf.org/html/rfc4880#section-5.13
*/
static int
@ -264,20 +266,7 @@ prefix_init(void **priv_p, void *arg, PullFilter *src)
if (buf[len - 2] != buf[len] || buf[len - 1] != buf[len + 1])
{
px_debug("prefix_init: corrupt prefix");
/*
* The original purpose of the 2-byte check was to show user a
* friendly "wrong key" message. This made following possible:
*
* "An Attack on CFB Mode Encryption As Used By OpenPGP" by Serge
* Mister and Robert Zuccherato
*
* To avoid being 'oracle', we delay reporting, which basically means
* we prefer to run into corrupt packet header.
*
* We _could_ throw PXE_PGP_CORRUPT_DATA here, but there is
* possibility of attack via timing, so we don't.
*/
/* report error in pgp_decrypt() */
ctx->corrupt_prefix = 1;
}
px_memset(tmpbuf, 0, sizeof(tmpbuf));
@ -788,12 +777,15 @@ parse_literal_data(PGP_Context *ctx, MBuf *dst, PullFilter *pkt)
}
px_memset(tmpbuf, 0, 4);
/* check if text */
/*
* If called from an SQL function that returns text, pgp_decrypt() rejects
* inputs not self-identifying as text.
*/
if (ctx->text_mode)
if (type != 't' && type != 'u')
{
px_debug("parse_literal_data: data type=%c", type);
return PXE_PGP_NOT_TEXT;
ctx->unexpected_binary = true;
}
ctx->unicode_mode = (type == 'u') ? 1 : 0;
@ -827,6 +819,7 @@ parse_compressed_data(PGP_Context *ctx, MBuf *dst, PullFilter *pkt)
int res;
uint8 type;
PullFilter *pf_decompr;
uint8 *discard_buf;
GETBYTE(pkt, type);
@ -850,7 +843,20 @@ parse_compressed_data(PGP_Context *ctx, MBuf *dst, PullFilter *pkt)
case PGP_COMPR_BZIP2:
px_debug("parse_compressed_data: bzip2 unsupported");
res = PXE_PGP_UNSUPPORTED_COMPR;
/* report error in pgp_decrypt() */
ctx->unsupported_compr = 1;
/*
* Discard the compressed data, allowing it to first affect any
* MDC digest computation.
*/
while (1)
{
res = pullf_read(pkt, 32 * 1024, &discard_buf);
if (res <= 0)
break;
}
break;
default:
@ -1168,8 +1174,36 @@ pgp_decrypt(PGP_Context *ctx, MBuf *msrc, MBuf *mdst)
if (res < 0)
return res;
/*
* Report a failure of the prefix_init() "quick check" now, rather than
* upon detection, to hinder timing attacks. pgcrypto is not generally
* secure against timing attacks, but this helps.
*/
if (!got_data || ctx->corrupt_prefix)
res = PXE_PGP_CORRUPT_DATA;
return PXE_PGP_CORRUPT_DATA;
/*
* Code interpreting purportedly-decrypted data prior to this stage shall
* report no error other than PXE_PGP_CORRUPT_DATA. (PXE_BUG is okay so
* long as it remains unreachable.) This ensures that an attacker able to
* choose a ciphertext and receive a corresponding decryption error
* message cannot use that oracle to gather clues about the decryption
* key. See "An Attack on CFB Mode Encryption As Used By OpenPGP" by
* Serge Mister and Robert Zuccherato.
*
* A problematic value in the first octet of a Literal Data or Compressed
* Data packet may indicate a simple user error, such as the need to call
* pgp_sym_decrypt_bytea instead of pgp_sym_decrypt. Occasionally,
* though, it is the first symptom of the encryption key not matching the
* decryption key. When this was the only problem encountered, report a
* specific error to guide the user; otherwise, we will have reported
* PXE_PGP_CORRUPT_DATA before now. A key mismatch makes the other errors
* into red herrings, and this avoids leaking clues to attackers.
*/
if (ctx->unsupported_compr)
return PXE_PGP_UNSUPPORTED_COMPR;
if (ctx->unexpected_binary)
return PXE_PGP_NOT_TEXT;
return res;
}

4
contrib/pgcrypto/pgp.h
View File

@ -153,7 +153,9 @@ struct PGP_Context
* internal variables
*/
int mdc_checked;
int corrupt_prefix;
int corrupt_prefix; /* prefix failed RFC 4880 "quick check" */
int unsupported_compr; /* has bzip2 compression */
int unexpected_binary; /* binary data seen in text_mode */
int in_mdc_pkt;
int use_mdcbuf_filter;
PX_MD *mdc_ctx;

3
contrib/pgcrypto/px.c
View File

@ -87,9 +87,6 @@ static const struct error_desc px_err_list[] = {
{PXE_PGP_UNSUPPORTED_PUBALGO, "Unsupported public key algorithm"},
{PXE_PGP_MULTIPLE_SUBKEYS, "Several subkeys not supported"},
/* fake this as PXE_PGP_CORRUPT_DATA */
{PXE_MBUF_SHORT_READ, "Corrupt data"},
{0, NULL},
};

2
contrib/pgcrypto/px.h
View File

@ -80,8 +80,6 @@ void px_free(void *p);
#define PXE_NO_RANDOM -17
#define PXE_DECRYPT_FAILED -18
#define PXE_MBUF_SHORT_READ -50
#define PXE_PGP_CORRUPT_DATA -100
#define PXE_PGP_CORRUPT_ARMOR -101
#define PXE_PGP_UNSUPPORTED_COMPR -102

45
contrib/pgcrypto/sql/pgp-decrypt.sql
View File

@ -268,3 +268,48 @@ a3nsOzKTXUfS9VyaXo8IrncM6n7fdaXpwba/3tNsAhJG4lDv1k4g9v8Ix2dfv6Rs
-- check BUG #11905, problem with messages 6 less than a power of 2.
select pgp_sym_decrypt(pgp_sym_encrypt(repeat('x',65530),'1'),'1') = repeat('x',65530);
-- expected: true
-- Negative tests
-- Decryption with a certain incorrect key yields an apparent Literal Data
-- packet reporting its content to be binary data. Ciphertext source:
-- iterative pgp_sym_encrypt('secret', 'key') until the random prefix gave
-- rise to that property.
select pgp_sym_decrypt(dearmor('
-----BEGIN PGP MESSAGE-----
ww0EBwMCxf8PTrQBmJdl0jcB6y2joE7GSLKRv7trbNsF5Z8ou5NISLUg31llVH/S0B2wl4bvzZjV
VsxxqLSPzNLAeIspJk5G
=mSd/
-----END PGP MESSAGE-----
'), 'wrong-key', 'debug=1');
-- Routine text/binary mismatch.
select pgp_sym_decrypt(pgp_sym_encrypt_bytea('P', 'key'), 'key', 'debug=1');
-- Decryption with a certain incorrect key yields an apparent BZip2-compressed
-- plaintext. Ciphertext source: iterative pgp_sym_encrypt('secret', 'key')
-- until the random prefix gave rise to that property.
select pgp_sym_decrypt(dearmor('
-----BEGIN PGP MESSAGE-----
ww0EBwMC9rK/dMkF5Zlt0jcBlzAQ1mQY2qYbKYbw8h3EZ5Jk0K2IiY92R82TRhWzBIF/8cmXDPtP
GXsd65oYJZp3Khz0qfyn
=Nmpq
-----END PGP MESSAGE-----
'), 'wrong-key', 'debug=1');
-- Routine use of BZip2 compression. Ciphertext source:
-- echo x | gpg --homedir /nonexistent --personal-compress-preferences bzip2 \
-- --personal-cipher-preferences aes --no-emit-version --batch \
-- --symmetric --passphrase key --armor
select pgp_sym_decrypt(dearmor('
-----BEGIN PGP MESSAGE-----
jA0EBwMCRhFrAKNcLVJg0mMBLJG1cCASNk/x/3dt1zJ+2eo7jHfjgg3N6wpB3XIe
QCwkWJwlBG5pzbO5gu7xuPQN+TbPJ7aQ2sLx3bAHhtYb0i3vV9RO10Gw++yUyd4R
UCAAw2JRIISttRHMfDpDuZJpvYo=
=AZ9M
-----END PGP MESSAGE-----
'), 'key', 'debug=1');

8
doc/src/sgml/pgcrypto.sgml
View File

@ -1270,6 +1270,14 @@ gen_random_uuid() returns uuid
<para>
If you cannot, then better do crypto inside client application.
</para>
<para>
The implementation does not resist
<ulink url="http://en.wikipedia.org/wiki/Side-channel_attack">side-channel
attacks</ulink>. For example, the time required for
a <filename>pgcrypto</> decryption function to complete varies among
ciphertexts of a given size.
</para>
</sect3>
<sect3>