Re: [BUGS] pgcrypto decrypt_iv() issue

#1

Stefan Kaltenbrunner <stefan (AT) kaltenbrunner (DOT) cc> writes:

Quote:

from some looking at the code in pgcrypto.c it seems to me that the
coding pattern in most functions there only checks for errors from the
corresponding initialization function, in the case of say decrypt_iv()
that means only the IV and the key are actually "validated" because that
is what the init function sees(it never sees that data!), if the actual
decrypt call fails (because the data is maybe a bit weird^broken) it
will happily ignore that and return random data.

Yeah. In pg_decrypt() we have

err = px_combo_init(c, (uint8 *) VARDATA(key), klen, NULL, 0);
if (!err)
err = px_combo_decrypt(c, (uint8 *) VARDATA(data), dlen,
(uint8 *) VARDATA(res), &rlen);

but in pg_decrypt_iv() it's just

err = px_combo_init(c, (uint8 *) VARDATA(key), klen,
(uint8 *) VARDATA(iv), ivlen);
if (!err)
px_combo_decrypt(c, (uint8 *) VARDATA(data), dlen,
(uint8 *) VARDATA(res), &rlen);

It looks to me like the result of px_combo_decrypt should be assigned to
"err" here. If I make that change, the test case you provide is
rejected:

ERROR: decrypt_iv error: Data not a multiple of block size

but the module's regression tests all still pass, indicating that this
sort of case isn't tested.

pg_encrypt_iv() has the identical usage error with respect to
px_combo_encrypt.

Marko, does this look right to you?

regards, tom lane

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#2

On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:

Quote:

Stefan Kaltenbrunner <stefan (AT) kaltenbrunner (DOT) cc> writes:
from some looking at the code in pgcrypto.c it seems to me that the
coding pattern in most functions there only checks for errors from the
corresponding initialization function, in the case of say decrypt_iv()
that means only the IV and the key are actually "validated" because that
is what the init function sees(it never sees that data!), if the actual
decrypt call fails (because the data is maybe a bit weird^broken) it
will happily ignore that and return random data.

Yeah. In pg_decrypt() we have

err = px_combo_init(c, (uint8 *) VARDATA(key), klen, NULL, 0);
if (!err)
err = px_combo_decrypt(c, (uint8 *) VARDATA(data), dlen,
(uint8 *) VARDATA(res), &rlen);

but in pg_decrypt_iv() it's just

err = px_combo_init(c, (uint8 *) VARDATA(key), klen,
(uint8 *) VARDATA(iv), ivlen);
if (!err)
px_combo_decrypt(c, (uint8 *) VARDATA(data), dlen,
(uint8 *) VARDATA(res), &rlen);

It looks to me like the result of px_combo_decrypt should be assigned to
"err" here. If I make that change, the test case you provide is
rejected:

ERROR: decrypt_iv error: Data not a multiple of block size

but the module's regression tests all still pass, indicating that this
sort of case isn't tested.

pg_encrypt_iv() has the identical usage error with respect to
px_combo_encrypt.

Marko, does this look right to you?

Yeah, it should be fixed. But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

pgcrypto.c is easily fixable and internal.c has proper checks.
But openssl.c does not. And I have a bigger openssl.c cleanup
pending. So I would prefer to add missing checks to cleaned-up
openssl.c and post them together (soonish).

But I'm bit unclear about fate of /contrib cleanup patches vs. 9.2,
so if they won't get in, it's ok to apply quick fixes to current tree,
it won't inconvinience me much.

--
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#3

Marko Kreen <markokr (AT) gmail (DOT) com> writes:

Quote:

pgcrypto.c is easily fixable and internal.c has proper checks.
But openssl.c does not. And I have a bigger openssl.c cleanup
pending. So I would prefer to add missing checks to cleaned-up
openssl.c and post them together (soonish).

But I'm bit unclear about fate of /contrib cleanup patches vs. 9.2,
so if they won't get in, it's ok to apply quick fixes to current tree,
it won't inconvinience me much.

I think we should fix and back-patch these two specific bugs. The
openssl.c change sounds like it might be something for HEAD only.

regards, tom lane

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#4

On 01/27/2012 04:20 PM, Marko Kreen wrote:

Quote:

On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
Stefan Kaltenbrunner <stefan (AT) kaltenbrunner (DOT) cc> writes:
from some looking at the code in pgcrypto.c it seems to me that the
coding pattern in most functions there only checks for errors from the
corresponding initialization function, in the case of say decrypt_iv()
that means only the IV and the key are actually "validated" because that
is what the init function sees(it never sees that data!), if the actual
decrypt call fails (because the data is maybe a bit weird^broken) it
will happily ignore that and return random data.

Yeah. In pg_decrypt() we have

err = px_combo_init(c, (uint8 *) VARDATA(key), klen, NULL, 0);
if (!err)
err = px_combo_decrypt(c, (uint8 *) VARDATA(data), dlen,
(uint8 *) VARDATA(res), &rlen);

but in pg_decrypt_iv() it's just

err = px_combo_init(c, (uint8 *) VARDATA(key), klen,
(uint8 *) VARDATA(iv), ivlen);
if (!err)
px_combo_decrypt(c, (uint8 *) VARDATA(data), dlen,
(uint8 *) VARDATA(res), &rlen);

It looks to me like the result of px_combo_decrypt should be assigned to
"err" here. If I make that change, the test case you provide is
rejected:

ERROR: decrypt_iv error: Data not a multiple of block size

but the module's regression tests all still pass, indicating that this
sort of case isn't tested.

pg_encrypt_iv() has the identical usage error with respect to
px_combo_encrypt.

Marko, does this look right to you?

Yeah, it should be fixed. But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

I agree - but in my case the input to those functions is actually coming
from external untrusted systems - so if the data is (completely) invalid
really want to get a proper error message instead of random memory content.

Quote:

pgcrypto.c is easily fixable and internal.c has proper checks.
But openssl.c does not. And I have a bigger openssl.c cleanup
pending. So I would prefer to add missing checks to cleaned-up
openssl.c and post them together (soonish).

hmm so openssl.c has similiar "issues" but you only want to fix them
together with a cleaned larger patch? sounds a bit of a problem for a
backpatch...

Stefan

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#5

On Fri, Jan 27, 2012 at 12:13:21PM -0500, Tom Lane wrote:

Quote:

Marko Kreen <markokr (AT) gmail (DOT) com> writes:
pgcrypto.c is easily fixable and internal.c has proper checks.
But openssl.c does not. And I have a bigger openssl.c cleanup
pending. So I would prefer to add missing checks to cleaned-up
openssl.c and post them together (soonish).

But I'm bit unclear about fate of /contrib cleanup patches vs. 9.2,
so if they won't get in, it's ok to apply quick fixes to current tree,
it won't inconvinience me much.

I think we should fix and back-patch these two specific bugs. The
openssl.c change sounds like it might be something for HEAD only.

Now I looked more in-depth and seems my comments were off - error
detection for encrypt()/decrypt() happens in px.c not in
internal.c/openssl.c. Latter ones simply validate internal APIs.

So attached patch should be enough to fix the issue.
And it should be quite backportable.

--
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#6

On Fri, Jan 27, 2012 at 7:34 PM, Stefan Kaltenbrunner
<stefan (AT) kaltenbrunner (DOT) cc> wrote:

Quote:

On 01/27/2012 04:20 PM, Marko Kreen wrote:
On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
Yeah, it should be fixed. *But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

I agree - but in my case the input to those functions is actually coming
from external untrusted systems - so if the data is (completely) invalid
really want to get a proper error message instead of random memory content.

You *will* get random memory content. If your app is exploitable with
invalid data, you *will* get exploited. The decrypt() checks are
more for developer convenience than anything more serious.

Please fix your app to survive invalid data...

--
marko

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#7

On Fri, Jan 27, 2012 at 18:54, Marko Kreen <markokr (AT) gmail (DOT) com> wrote:

Quote:

On Fri, Jan 27, 2012 at 7:34 PM, Stefan Kaltenbrunner
stefan (AT) kaltenbrunner (DOT) cc> wrote:
On 01/27/2012 04:20 PM, Marko Kreen wrote:
On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
Yeah, it should be fixed. *But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

I agree - but in my case the input to those functions is actually coming
from external untrusted systems - so if the data is (completely) invalid
really want to get a proper error message instead of random memory content.

You *will* get random memory content. *If your app is exploitable with
invalid data, you *will* get exploited. *The decrypt() checks are
more for developer convenience than anything more serious.

Hold on. I hope there's some misunderstanding here.

I hope you are you saying that feeding random data to the decrypt
functions should be expected to return random data out of previously
free()d areas? Surely you're not?

Obviouly, if you send in invalid data or an invalid key, it will
decrypt into incorrect data, that goes without saying. But it should
still be the same block size and not contain random unrelated memory
blocks, shouldn' it?

--
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*Me: http://www.hagander.net/
*Work: http://www.redpill-linpro.com/

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#8

On Fri, Jan 27, 2012 at 8:00 PM, Magnus Hagander <magnus (AT) hagander (DOT) net> wrote:

Quote:

On Fri, Jan 27, 2012 at 18:54, Marko Kreen <markokr (AT) gmail (DOT) com> wrote:
On Fri, Jan 27, 2012 at 7:34 PM, Stefan Kaltenbrunner
stefan (AT) kaltenbrunner (DOT) cc> wrote:
On 01/27/2012 04:20 PM, Marko Kreen wrote:
On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
Yeah, it should be fixed. *But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

I agree - but in my case the input to those functions is actually coming
from external untrusted systems - so if the data is (completely) invalid
really want to get a proper error message instead of random memory content.

You *will* get random memory content. *If your app is exploitable with
invalid data, you *will* get exploited. *The decrypt() checks are
more for developer convenience than anything more serious.

Hold on. I hope there's some misunderstanding here.

I hope you are you saying that feeding random data to the decrypt
functions should be expected to return random data out of previously
free()d areas? Surely you're not?

Obviouly, if you send in invalid data or an invalid key, it will
decrypt into incorrect data, that goes without saying. But it should
still be the same block size and not contain random unrelated memory
blocks, shouldn' it?

Yes, it should not contain unrelated data.

--
marko

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#9

On 01/27/2012 07:06 PM, Marko Kreen wrote:

Quote:

On Fri, Jan 27, 2012 at 8:00 PM, Magnus Hagander <magnus (AT) hagander (DOT) net> wrote:
On Fri, Jan 27, 2012 at 18:54, Marko Kreen <markokr (AT) gmail (DOT) com> wrote:
On Fri, Jan 27, 2012 at 7:34 PM, Stefan Kaltenbrunner
stefan (AT) kaltenbrunner (DOT) cc> wrote:
On 01/27/2012 04:20 PM, Marko Kreen wrote:
On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
Yeah, it should be fixed. But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

I agree - but in my case the input to those functions is actually coming
from external untrusted systems - so if the data is (completely) invalid
really want to get a proper error message instead of random memory content.

You *will* get random memory content. If your app is exploitable with
invalid data, you *will* get exploited. The decrypt() checks are
more for developer convenience than anything more serious.

Hold on. I hope there's some misunderstanding here.

I hope you are you saying that feeding random data to the decrypt
functions should be expected to return random data out of previously
free()d areas? Surely you're not?

Obviouly, if you send in invalid data or an invalid key, it will
decrypt into incorrect data, that goes without saying. But it should
still be the same block size and not contain random unrelated memory
blocks, shouldn' it?

Yes, it should not contain unrelated data.

hmm - see the last example I had in my original report - not sure i
consider the path to pgcrypto.so "related" data and I most definitly do
not expect to get that back from sending invalid data to the database...

Stefan

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#10

On Fri, Jan 27, 2012 at 8:10 PM, Stefan Kaltenbrunner
<stefan (AT) kaltenbrunner (DOT) cc> wrote:

Quote:

On 01/27/2012 07:06 PM, Marko Kreen wrote:
On Fri, Jan 27, 2012 at 8:00 PM, Magnus Hagander <magnus (AT) hagander (DOT) net> wrote:
On Fri, Jan 27, 2012 at 18:54, Marko Kreen <markokr (AT) gmail (DOT) com> wrote:
On Fri, Jan 27, 2012 at 7:34 PM, Stefan Kaltenbrunner
stefan (AT) kaltenbrunner (DOT) cc> wrote:
On 01/27/2012 04:20 PM, Marko Kreen wrote:
On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
Yeah, it should be fixed. *But note that "random data" is part of
decrypt() spec - the validation it can do is a joke.

Its more important to do proper checks in encrypt() to avoid invalid
stored data, but there the recommended modes (CBC, CFB) can work
with any length data, so even there the impact is low.

I agree - but in my case the input to those functions is actually coming
from external untrusted systems - so if the data is (completely) invalid
really want to get a proper error message instead of random memory content.

You *will* get random memory content. *If your app is exploitable with
invalid data, you *will* get exploited. *The decrypt() checks are
more for developer convenience than anything more serious.

Hold on. I hope there's some misunderstanding here.

I hope you are you saying that feeding random data to the decrypt
functions should be expected to return random data out of previously
free()d areas? Surely you're not?

Obviouly, if you send in invalid data or an invalid key, it will
decrypt into incorrect data, that goes without saying. But it should
still be the same block size and not contain random unrelated memory
blocks, shouldn' it?

Yes, it should not contain unrelated data.

hmm - see the last example I had in my original report - not sure i
consider the path to pgcrypto.so "related" data and I most definitly do
not expect to get that back from sending invalid data to the database...

Yeah, the bug causes return of palloced but uninitialized data.
That needs to be fixed.

--
marko

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