Commit Graph

65 Commits

Author SHA1 Message Date
David Benjamin
08d774a45f Remove some easy bn_set_minimal_width calls.
Functions that deserialize from bytes and Montgomery multiplication have
no reason to minimize their inputs.

Bug: 232
Change-Id: I121cc9b388033d684057b9df4ad0c08364849f58
Reviewed-on: https://boringssl-review.googlesource.com/25258
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-02-05 23:47:14 +00:00
David Benjamin
09633cc34e Rename bn->top to bn->width.
This has no behavior change, but it has a semantic one. This CL is an
assertion that all BIGNUM functions tolerate non-minimal BIGNUMs now.
Specifically:

- Functions that do not touch top/width are assumed to not care.

- Functions that do touch top/width will be changed by this CL. These
  should be checked in review that they tolerate non-minimal BIGNUMs.

Subsequent CLs will start adjusting the widths that BIGNUM functions
output, to fix timing leaks.

Bug: 232
Change-Id: I3a2b41b071f2174452f8d3801bce5c78947bb8f7
Reviewed-on: https://boringssl-review.googlesource.com/25257
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-02-05 23:44:24 +00:00
David Benjamin
23223ebbc1 Tidy BN_bn2hex and BN_print with non-minimal inputs.
These actually work as-is, but BN_bn2hex allocates more memory than
necessary, and we may as well skip the unnecessary words where we can.
Also add a test for this.

Bug: 232
Change-Id: Ie271fe9f3901d00dd5c3d7d63c1776de81a10ec7
Reviewed-on: https://boringssl-review.googlesource.com/25304
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-02-05 23:18:33 +00:00
David Benjamin
226b4b51b5 Make the rest of BIGNUM accept non-minimal values.
Test this by re-running bn_tests.txt tests a lot. For the most part,
this was done by scattering bn_minimal_width or bn_correct_top calls as
needed. We'll incrementally tease apart the functions that need to act
on non-minimal BIGNUMs in constant-time.

BN_sqr was switched to call bn_correct_top at the end, rather than
sample bn_minimal_width, in anticipation of later splitting it into
BN_sqr (for calculators) and BN_sqr_fixed (for BN_mod_mul_montgomery).

BN_div_word also uses bn_correct_top because it calls BN_lshift so
officially shouldn't rely on BN_lshift returning something
minimal-width, though I expect we'd want to split off a BN_lshift_fixed
than change that anyway?

The shifts sample bn_minimal_width rather than bn_correct_top because
they all seem to try to be very clever around the bit width. If we need
constant-time versions of them, we can adjust them later.

Bug: 232
Change-Id: Ie17b39034a713542dbe906cf8954c0c5483c7db7
Reviewed-on: https://boringssl-review.googlesource.com/25255
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-02-05 23:05:34 +00:00
David Benjamin
f4b708cc1e Add a function which folds BN_MONT_CTX_{new,set} together.
These empty states aren't any use to either caller or implementor.

Change-Id: If0b748afeeb79e4a1386182e61c5b5ecf838de62
Reviewed-on: https://boringssl-review.googlesource.com/25254
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 20:23:25 +00:00
David Benjamin
feffb87168 Make BN_bn2bin_padded work with non-minimal BIGNUMs.
Checking the excess words for zero doesn't need to be in constant time,
but it's free. BN_bn2bin_padded is a little silly as read_word_padded
only exists to work around bn->top being minimal. Once non-minimal
BIGNUMs are turned on and the RSA code works right, we can simplify
BN_bn2bin_padded.

Bug: 232
Change-Id: Ib81e30ca1e5a8ea90ab3278bf4ded219bac481ac
Reviewed-on: https://boringssl-review.googlesource.com/25253
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 20:16:50 +00:00
David Benjamin
6c41465548 Remove redundant bn->top computation.
One less to worry about.

Bug: 232
Change-Id: Ib7d38e18fee02590088d76363e17f774cfefa59b
Reviewed-on: https://boringssl-review.googlesource.com/25252
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:54:09 +00:00
David Benjamin
7979dbede2 Use bn_resize_words in BN_from_montgomery_word.
Saves a bit of work, and we get a width sanity-check.

Bug: 232
Change-Id: I1c6bc376c9d8aaf60a078fdc39f35b6f44a688c6
Reviewed-on: https://boringssl-review.googlesource.com/25251
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:52:49 +00:00
David Benjamin
76ce04bec8 Fix up BN_MONT_CTX_set with non-minimal values.
Give a non-minimal modulus, there are two possible values of R we might
pick: 2^(BN_BITS2 * width) or 2^(BN_BITS2 * bn_minimal_width).
Potentially secret moduli would make the former attractive and things
might even work, but our only secret moduli (RSA) have public bit
widths. It's more cases to test and the usual BIGNUM invariant is that
widths do not affect numerical output.

Thus, settle on minimizing mont->N for now. With the top explicitly made
minimal, computing |lgBigR| is also a little simpler.

This CL also abstracts out the < R check in the RSA code, and implements
it in a width-agnostic way.

Bug: 232
Change-Id: I354643df30530db7866bb7820e34241d7614f3c2
Reviewed-on: https://boringssl-review.googlesource.com/25250
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:52:15 +00:00
David Benjamin
0758b6837e Reject negative numbers in BN_{mod_mul,to,from}_montgomery.
These functions already require their inputs to be reduced mod N (or, in
some cases, bounded by R or N*R), so negative numbers are nonsense.  The
code still attempted to account for them by working on the absolute
value and fiddling with the sign bit. (The output would be in range (-N,
N) instead of [0, N).)

This complicates relaxing bn_correct_top because bn_correct_top is also
used to prevent storing a negative zero. Instead, just reject negative
inputs.

Upgrade-Note: These functions are public API, so some callers may
    notice. Code search suggests there is only one caller outside
    BoringSSL, and it looks fine.

Bug: 232
Change-Id: Ieba3acbb36b0ff6b72b8ed2b14882ec9b88e4665
Reviewed-on: https://boringssl-review.googlesource.com/25249
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:44:54 +00:00
David Benjamin
9a5bfc0350 Tidy up BN_mod_mul_montgomery.
This matches bn_mod_mul_montgomery_small and removes a bit of
unnecessary stuttering.

Change-Id: Ife249c6e8754aef23c144dbfdea5daaf7ed9f48a
Reviewed-on: https://boringssl-review.googlesource.com/25248
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:44:01 +00:00
David Benjamin
2ccdf584aa Factor out BN_to_montgomery(1) optimization.
This cuts down on a duplicated place where we mess with bn->top. It also
also better abstracts away what determines the value of R.

(I ordered this wrong and rebasing will be annoying. Specifically, the
question is what happens if the modulus is non-minimal. In
https://boringssl-review.googlesource.com/c/boringssl/+/25250/, R will
be determined by the stored width of mont->N, so we want to use mont's
copy of the modulus. Though, one way or another, the important part is
that it's inside the Montgomery abstraction.)

Bug: 232
Change-Id: I74212e094c8a47f396b87982039e49048a130916
Reviewed-on: https://boringssl-review.googlesource.com/25247
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:42:39 +00:00
David Benjamin
dc8b1abb75 Do RSA sqrt(2) business in BIGNUM.
This is actually a bit more complicated (the mismatching widths cases
will never actually happen in RSA), but it's easier to think about and
removes more width-sensitive logic.

Bug: 232
Change-Id: I85fe6e706be1f7d14ffaf587958e930f47f85b3c
Reviewed-on: https://boringssl-review.googlesource.com/25246
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:32:32 +00:00
David Benjamin
43cf27e7d7 Add bn_copy_words.
This makes it easier going to and from non-minimal BIGNUMs and words
without worrying about the widths which are ultimately to become less
friendly.

Bug: 232
Change-Id: Ia57cb29164c560b600573c27b112ad9375a86aad
Reviewed-on: https://boringssl-review.googlesource.com/25245
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:24:39 +00:00
David Benjamin
ad5cfdf541 Add initial support for non-minimal BIGNUMs.
Thanks to Andres Erbsen for extremely helpful suggestions on how finally
plug this long-standing hole!

OpenSSL BIGNUMs are currently minimal-width, which means they cannot be
constant-time. We'll need to either excise BIGNUM from RSA and EC or
somehow fix BIGNUM. EC_SCALAR and later EC_FELEM work will excise it
from EC, but RSA's BIGNUMs are more transparent.  Teaching BIGNUM to
handle non-minimal word widths is probably simpler.

The main constraint is BIGNUM's large "calculator" API surface. One
could, in theory, do arbitrary math on RSA components, which means all
public functions must tolerate non-minimal inputs. This is also useful
for EC; https://boringssl-review.googlesource.com/c/boringssl/+/24445 is
silly.

As a first step, fix comparison-type functions that were assuming
minimal BIGNUMs. I've also added bn_resize_words, but it is testing-only
until the rest of the library is fixed.

bn->top is now a loose upper bound we carry around. It does not affect
numerical results, only performance and secrecy. This is a departure
from the original meaning, and compiler help in auditing everything is
nice, so the final change in this series will rename bn->top to
bn->width. Thus these new functions are named per "width", not "top".

Looking further ahead, how are output BIGNUM widths determined? There's
three notions of correctness here:

1. Do I compute the right answer for all widths?

2. Do I handle secret data in constant time?

3. Does my memory usage not balloon absurdly?

For (1), a BIGNUM function must give the same answer for all input
widths. BN_mod_add_quick may assume |a| < |m|, but |a| may still be
wider than |m| by way of leading zeres. The simplest approach is to
write code in a width-agnostic way and rely on functions to accept all
widths. Where functions need to look at bn->d, we'll a few helper
functions to smooth over funny widths.

For (2), (1) is little cumbersome. Consider constant-time modular
addition. A sane type system would guarantee input widths match. But C
is weak here, and bifurcating the internals is a lot of work. Thus, at
least for now, I do not propose we move RSA's internal computation out
of BIGNUM. (EC_SCALAR/EC_FELEM are valuable for EC because we get to
stack-allocate, curves were already specialized, and EC only has two
types with many operations on those types. None of these apply to RSA.
We've got numbers mod n, mod p, mod q, and their corresponding
exponents, each of which is used for basically one operation.)

Instead, constant-time BIGNUM functions will output non-minimal widths.
This is trivial for BN_bin2bn or modular arithmetic. But for BN_mul,
constant-time[*] would dictate r->top = a->top + b->top. A calculator
repeatedly multiplying by one would then run out of memory.  Those we'll
split into a private BN_mul_fixed for crypto, leaving BN_mul for
calculators. BN_mul is just BN_mul_fixed followed by bn_correct_top.

[*] BN_mul is not constant-time for other reasons, but that will be
fixed separately.

Bug: 232
Change-Id: Ide2258ae8c09a9a41bb71d6777908d1c27917069
Reviewed-on: https://boringssl-review.googlesource.com/25244
Reviewed-by: Adam Langley <agl@google.com>
2018-02-02 18:03:46 +00:00
David Benjamin
32b5940267 Don't leak the exponent bit width in BN_mod_exp_mont_consttime.
(See also https://github.com/openssl/openssl/pull/5154.)

The exponent here is one of d, dmp1, or dmq1 for RSA. This value and its
bit length are both secret. The only public upper bound is the bit width
of the corresponding modulus (RSA n, p, and q, respectively).

Although BN_num_bits is constant-time (sort of; see bn_correct_top notes
in preceding patch), this does not fix the root problem, which is that
the windows are based on the minimal bit width, not the upper bound. We
could use BN_num_bits(m), but BN_mod_exp_mont_consttime is public API
and may be called with larger exponents. Instead, use all top*BN_BITS2
bits in the BIGNUM. This is still sensitive to the long-standing
bn_correct_top leak, but we need to fix that regardless.

This may cause us to do a handful of extra multiplications for RSA keys
which are just above a whole number of words, but that is not a standard
RSA key size.

Change-Id: I5e2f12b70c303b27c597a7e513b7bf7288f7b0e3
Reviewed-on: https://boringssl-review.googlesource.com/25185
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-01-23 22:27:37 +00:00
David Benjamin
8017cdde38 Make BN_num_bits_word constant-time.
(The BN_num_bits_word implementation was originally written by Andy
Polyakov for OpenSSL. See also
https://github.com/openssl/openssl/pull/5154.)

BN_num_bits, by way of BN_num_bits_word, currently leaks the
most-significant word of its argument via branching and memory access
pattern.

BN_num_bits is called on RSA prime factors in various places. These have
public bit lengths, but all bits beyond the high bit are secret. This
fully resolves those cases.

There are a few places where BN_num_bits is called on an input where
the bit length is also secret. The two left in BoringSSL are:

- BN_mod_exp_mont_consttime calls it on the RSA private exponent.

- The timing "fix" to add the order to k in DSA.

This does *not* fully resolve those cases as we still only look at the
top word. Today, that is guaranteed to be non-zero, but only because of
the long-standing bn_correct_top timing leak. Once that is fixed (I hope
to have patches soon), a constant-time BN_num_bits on such inputs must
count bits on each word.

Instead, those cases should not call BN_num_bits at all. The former uses
the bit width to pick windows, but it should be using the maximum bit
width. The next patch will fix this.  The latter is the same "fix" we
excised from ECDSA in a838f9dc7e.  That
should be excised from DSA after the bn_correct_top bug is fixed.

Thanks to Dinghao Wu, Danfeng Zhang, Shuai Wang, Pei Wang, and Xiao Liu
for reporting this issue.

Change-Id: Idc3da518cc5ec18bd8688b95f959b15300a57c14
Reviewed-on: https://boringssl-review.googlesource.com/25184
Reviewed-by: Adam Langley <agl@google.com>
2018-01-23 22:14:54 +00:00
David Benjamin
875095aa7c Silence ARMv8 deprecated IT instruction warnings.
ARMv8 kindly deprecated most of its IT instructions in Thumb mode.
These files are taken from upstream and are used on both ARMv7 and ARMv8
processors. Accordingly, silence the warnings by marking the file as
targetting ARMv7. In other files, they were accidentally silenced anyway
by way of the existing .arch lines.

This can be reproduced by building with the new NDK and passing
-DCMAKE_ASM_FLAGS=-march=armv8-a. Some of our downstream code ends up
passing that to the assembly.

Note this change does not attempt to arrange for ARMv8-A/T32 to get
code which honors the constraints. It only silences the warnings and
continues to give it the same ARMv7-A/Thumb-2 code that backwards
compatibility dictates it continue to run.

Bug: chromium:575886, b/63131949
Change-Id: I24ce0b695942eaac799347922b243353b43ad7df
Reviewed-on: https://boringssl-review.googlesource.com/24166
Reviewed-by: Adam Langley <agl@google.com>
2017-12-14 01:56:22 +00:00
David Benjamin
6fe960d174 Enable __asm__ and uint128_t code in clang-cl.
It actually works fine. I just forgot one of the typedefs last time.
This gives a roughly 2x improvement on P-256 in clang-cl +
OPENSSL_SMALL, the configuration used by Chrome.

Before:
Did 1302 ECDH P-256 operations in 1015000us (1282.8 ops/sec)
Did 4250 ECDSA P-256 signing operations in 1047000us (4059.2 ops/sec)
Did 1750 ECDSA P-256 verify operations in 1094000us (1599.6 ops/sec)

After:
Did 3250 ECDH P-256 operations in 1078000us (3014.8 ops/sec)
Did 8250 ECDSA P-256 signing operations in 1016000us (8120.1 ops/sec)
Did 3250 ECDSA P-256 verify operations in 1063000us (3057.4 ops/sec)

(These were taken on a VM, so the measurements are extremely noisy, but
this sort of improvement is visible regardless.)

Alas, we do need a little extra bit of fiddling because division does
not work (crbug.com/787617).

Bug: chromium:787617
Update-Note: This removes the MSan uint128_t workaround which does not
    appear to be necessary anymore.
Change-Id: I8361314608521e5bdaf0e7eeae7a02c33f55c69f
Reviewed-on: https://boringssl-review.googlesource.com/23984
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-12-11 22:46:26 +00:00
David Benjamin
296a61d600 bn/asm/rsaz-avx2.pl: fix digit correction bug in rsaz_1024_mul_avx2.
Credit to OSS-Fuzz for finding this.

CVE-2017-3738

(Imported from upstream's 5630661aecbea5fe3c4740f5fea744a1f07a6253 and
77d75993651b63e872244a3256e37967bb3c3e9e.)

Confirmed with Intel SDE that the fix makes the test vector pass and
that, without the fix, the test vector does not. (Well, we knew the
latter already, since it was our test vector.)

Change-Id: I167aa3407ddab3b434bacbd18e099c55aa40ac4c
Reviewed-on: https://boringssl-review.googlesource.com/23884
Reviewed-by: Adam Langley <agl@google.com>
2017-12-07 16:54:32 +00:00
Adam Langley
bc37ad91fe Fix alignment-violating cast.
Change-Id: Id8b69bb6103dd938f4c6d0d2ec24f3d50ba5513c
Update-Note: fixes b/70034392
Reviewed-on: https://boringssl-review.googlesource.com/23744
Commit-Queue: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-12-01 22:32:17 +00:00
David Benjamin
a838f9dc7e Make ECDSA signing 10% faster and plug some timing leaks.
None of the asymmetric crypto we inherented from OpenSSL is
constant-time because of BIGNUM. BIGNUM chops leading zeros off the
front of everything, so we end up leaking information about the first
word, in theory. BIGNUM functions additionally tend to take the full
range of inputs and then call into BN_nnmod at various points.

All our secret values should be acted on in constant-time, but k in
ECDSA is a particularly sensitive value. So, ecdsa_sign_setup, in an
attempt to mitigate the BIGNUM leaks, would add a couple copies of the
order.

This does not work at all. k is used to compute two values: k^-1 and kG.
The first operation when computing k^-1 is to call BN_nnmod if k is out
of range. The entry point to our tuned constant-time curve
implementations is to call BN_nnmod if the scalar has too many bits,
which this causes. The result is both corrections are immediately undone
but cause us to do more variable-time work in the meantime.

Replace all these computations around k with the word-based functions
added in the various preceding CLs. In doing so, replace the BN_mod_mul
calls (which internally call BN_nnmod) with Montgomery reduction. We can
avoid taking k^-1 out of Montgomery form, which combines nicely with
Brian Smith's trick in 3426d10119. Along
the way, we avoid some unnecessary mallocs.

BIGNUM still affects the private key itself, as well as the EC_POINTs.
But this should hopefully be much better now. Also it's 10% faster:

Before:
Did 15000 ECDSA P-224 signing operations in 1069117us (14030.3 ops/sec)
Did 18000 ECDSA P-256 signing operations in 1053908us (17079.3 ops/sec)
Did 1078 ECDSA P-384 signing operations in 1087853us (990.9 ops/sec)
Did 473 ECDSA P-521 signing operations in 1069835us (442.1 ops/sec)

After:
Did 16000 ECDSA P-224 signing operations in 1064799us (15026.3 ops/sec)
Did 19000 ECDSA P-256 signing operations in 1007839us (18852.2 ops/sec)
Did 1078 ECDSA P-384 signing operations in 1079413us (998.7 ops/sec)
Did 484 ECDSA P-521 signing operations in 1083616us (446.7 ops/sec)

Change-Id: I2a25e90fc99dac13c0616d0ea45e125a4bd8cca1
Reviewed-on: https://boringssl-review.googlesource.com/23075
Reviewed-by: Adam Langley <agl@google.com>
2017-11-22 22:51:40 +00:00
David Benjamin
02514002fd Use dec/jnz instead of loop in bn_add_words and bn_sub_words.
Imported from upstream's a78324d95bd4568ce2c3b34bfa1d6f14cddf92ef. I
think the "regression" part of that change is some tweak to BN_usub and
I guess the bn_*_words was to compensate for it, but we may as well
import it. Apparently the loop instruction is terrible.

Before:
Did 39871000 bn_add_words operations in 1000002us (39870920.3 ops/sec)
Did 38621750 bn_sub_words operations in 1000001us (38621711.4 ops/sec)

After:
Did 64012000 bn_add_words operations in 1000007us (64011551.9 ops/sec)
Did 81792250 bn_sub_words operations in 1000002us (81792086.4 ops/sec)

loop sets no flags (even doing the comparison to zero without ZF) while
dec sets all flags but CF, so Andres and I are assuming that because
this prevents Intel from microcoding it to dec/jnz, they otherwise can't
be bothered to add more circuitry since every compiler has internalized
by now to never use loop.

Change-Id: I3927cd1c7b707841bbe9963e3d4afd7ba9bd9b36
Reviewed-on: https://boringssl-review.googlesource.com/23344
Reviewed-by: Adam Langley <agl@google.com>
2017-11-22 21:56:05 +00:00
Adam Langley
8c565fa86c Include a couple of missing header files.
mem.h for |OPENSSL_cleanse| and bn/internal.h for things like
|bn_less_than_words| and |bn_correct_top|.

Change-Id: I3c447a565dd9e4f18fb2ff5d59f80564b4df8cea
Reviewed-on: https://boringssl-review.googlesource.com/23164
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 20:36:38 +00:00
David Benjamin
a08bba51a5 Add bn_mod_exp_mont_small and bn_mod_inverse_prime_mont_small.
These can be used to invert values in ECDSA. Unlike their BIGNUM
counterparts, the caller is responsible for taking values in and out of
Montgomery domain. This will save some work later on in the ECDSA
computation.

Change-Id: Ib7292900a0fdeedce6cb3e9a9123c94863659043
Reviewed-on: https://boringssl-review.googlesource.com/23071
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:23:48 +00:00
David Benjamin
40e4ecb793 Add "small" variants of Montgomery logic.
These use the square and multiply functions added earlier.

Change-Id: I723834f9a227a9983b752504a2d7ce0223c43d24
Reviewed-on: https://boringssl-review.googlesource.com/23070
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:23:01 +00:00
David Benjamin
a01aa9aa9f Split BN_from_montgomery_word into a non-BIGNUM core.
bn_from_montgomery_in_place is actually constant-time. It is, of course,
only used by non-constant-time BIGNUM callers, but that will soon be
fixed.

Change-Id: I2b2c9943dc3b8d6a4b5b19a5bc4fa9ebad532bac
Reviewed-on: https://boringssl-review.googlesource.com/23069
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:22:43 +00:00
David Benjamin
6bc18a3bd4 Add bn_mul_small and bn_sqr_small.
As part of excising BIGNUM from EC scalars, we will need a "words"
version of BN_mod_mul_montgomery. That, in turn, requires BN_sqr and
BN_mul for cases where we don't have bn_mul_mont.

BN_sqr and BN_mul have a lot of logic in there, with the most complex
cases being not even remotely constant time. Fortunately, those only
apply to RSA-sized numbers, not EC-sized numbers. (With the exception, I
believe, of 32-bit P-521 which just barely exceeds the cutoff.) Imposing
a limit also makes it easier to stack-allocate temporaries (BN_CTX
serves a similar purpose in BIGNUM).

Extract bn_mul_small and bn_sqr_small and test them as part of
bn_tests.txt. Later changes will build on these.

If we end up reusing these functions for RSA in the future (though that
would require tending to the egregiously non-constant-time code in the
no-asm build), we probably want to extract a version where there is an
explicit tmp parameter as in bn_sqr_normal rather than the stack bits.

Change-Id: If414981eefe12d6664ab2f5e991a359534aa7532
Reviewed-on: https://boringssl-review.googlesource.com/23068
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:22:30 +00:00
David Benjamin
64619deaa3 Const-correct some of the low-level BIGNUM functions.
Change-Id: I8c6257e336f54a3a1786df9c4103fcf29177030a
Reviewed-on: https://boringssl-review.googlesource.com/23067
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:20:40 +00:00
David Benjamin
bd275702d2 size_t a bunch of bn words bits.
Also replace a pointless call to bn_mul_words with a memset.

Change-Id: Ief30ddab0e84864561b73fe2776bd0477931cf7f
Reviewed-on: https://boringssl-review.googlesource.com/23066
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:20:28 +00:00
David Benjamin
73df153be8 Make BN_generate_dsa_nonce internally constant-time.
This rewrites the internals with a "words" variant that can avoid
bn_correct_top. It still ultimately calls bn_correct_top as the calling
convention is sadly still BIGNUM, but we can lift that calling
convention out incrementally.

Performance seems to be comparable, if not faster.

Before:
Did 85000 ECDSA P-256 signing operations in 5030401us (16897.3 ops/sec)
Did 34278 ECDSA P-256 verify operations in 5048029us (6790.4 ops/sec)

After:
Did 85000 ECDSA P-256 signing operations in 5021057us (16928.7 ops/sec)
Did 34086 ECDSA P-256 verify operations in 5010416us (6803.0 ops/sec)

Change-Id: I1159746dfcc00726dc3f28396076a354556e6e7d
Reviewed-on: https://boringssl-review.googlesource.com/23065
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:18:30 +00:00
David Benjamin
b25140c7b6 Fix timing leak in BN_from_montgomery_word.
BN_from_montgomery_word doesn't have a constant memory access pattern.
Replace the pointer trick with constant_time_select_w. There is, of
course, still the bn_correct_top leak pervasive in BIGNUM itself.

I wasn't able to measure a performance on RSA operations before or after
this change, but the benchmarks would vary wildly run to run. But one
would assume the logic here is nothing compared to the actual reduction.

Change-Id: Ide761fde3a091a93679f0a803a287aa5d0d4600d
Reviewed-on: https://boringssl-review.googlesource.com/22904
Reviewed-by: Adam Langley <agl@google.com>
2017-11-20 16:18:09 +00:00
David Benjamin
d66bbf3413 Tidy up BN_mod_exp_mont.
This was primarily for my own understanding, but this should hopefully
also be clearer and more amenable to using unsigned indices later.

Change-Id: I09cc3d55de0f7d9284d3b3168d8b0446274b2ab7
Reviewed-on: https://boringssl-review.googlesource.com/22889
Reviewed-by: Adam Langley <agl@google.com>
2017-11-10 22:43:54 +00:00
David Benjamin
607f9807e5 Remove BN_TBIT.
Normal shifts do the trick just fine and are less likely to tempt the
compiler into inserting a jump.

Change-Id: Iaa1da1b6f986fd447694fcde8f3525efb9eeaf11
Reviewed-on: https://boringssl-review.googlesource.com/22888
Reviewed-by: Adam Langley <agl@google.com>
2017-11-10 22:43:37 +00:00
David Benjamin
bf3f6caaf3 Document some BIGNUM internals.
Change-Id: I8f044febf16afe04da8b176c638111a9574c4d02
Reviewed-on: https://boringssl-review.googlesource.com/22887
Reviewed-by: Adam Langley <agl@google.com>
2017-11-10 22:43:13 +00:00
David Benjamin
0a9222b824 Fix comment typo.
Change-Id: I482093000ee2e4ba371c78b4f7f8e8b121e71640
Reviewed-on: https://boringssl-review.googlesource.com/22886
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
2017-11-10 22:22:42 +00:00
Daniel Hirche
d5dda9b803 Align |BN_div| with its documentation.
Change-Id: Idd0dc9dafb4ea9adbf22257018138c49f7980fee
Reviewed-on: https://boringssl-review.googlesource.com/22604
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-11-06 22:55:30 +00:00
Daniel Hirche
2eb2889702 bn/exp: don't check |copy_to_prebuf|'s retval in |BN_mod_exp_mont_consttime|.
It always returns one, so just void it.

Change-Id: I8733cc3d6b20185e782cf0291e9c0dc57712bb63
Reviewed-on: https://boringssl-review.googlesource.com/22564
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-11-03 15:43:52 +00:00
David Benjamin
2d07d30c44 bn/asm/x86_64-mont5.pl: fix carry bug in bn_sqrx8x_internal.
Credit to OSS-Fuzz for finding this.

CVE-2017-3736

(Imported from upstream's 668a709a8d7ea374ee72ad2d43ac72ec60a80eee and
420b88cec8c6f7c67fad07bf508dcccab094f134.)

This bug does not affect BoringSSL as we do not enable the ADX code.
Note the test vector had to be tweaked to take things in and out of
Montgomery form. (There may be something to be said for test vectors for
just BN_mod_mul_montgomery, though we'd need separate 64-bit and 32-bit
ones because R can be different.)

Change-Id: I832070731ac1c5f893f9c1746892fc4a32f023f5
Reviewed-on: https://boringssl-review.googlesource.com/22484
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-11-02 17:07:57 +00:00
David Benjamin
4281bcd5d2 Revert assembly changes in "Hide CPU capability symbols in C."
This partially reverts commit 38636aba74.
Some build on Android seems to break now. I'm not really sure what the
situation is, but if the weird common symbols are still there (can we
remove them?), they probably ought to have the right flags.

Change-Id: Ief589d763d16b995ac6be536505acf7596a87b30
Reviewed-on: https://boringssl-review.googlesource.com/22404
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-30 20:39:57 +00:00
David Benjamin
8f06074a91 Handle malloc failures better in bn_test.cc.
Those EXPECTs should be ASSERTs to ensure bn is not null.

Change-Id: Icb54c242ffbde5f8eaa67f19f214c9eef13705ea
Reviewed-on: https://boringssl-review.googlesource.com/22366
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-30 18:53:48 +00:00
David Benjamin
af92418b8b Generate bn_div and bn_mod_exp corpus from bn_tests.txt.
Also switch them to accepting a u16 length prefix. We appear not to have
any such tests right now, but RSA-2048 would involve modulus well larger
and primes just a hair larger than a u8 length prefix alows.

Change-Id: Icce8f1d976e159b945302fbba732e72913c7b724
Reviewed-on: https://boringssl-review.googlesource.com/22284
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-27 18:57:48 +00:00
David Benjamin
fed560ff2a Clear no-op BN_MASK2 masks.
This is an OpenSSL thing to support platforms where BN_ULONG is not
actually the size it claims to be. We define BN_ULONG to uint32_t and
uint64_t which are guaranteed by C to implement arithemetic modulo 2^32
and 2^64, respectively. Thus there is no need for any of this.

Change-Id: I098cd4cc050a136b9f2c091dfbc28dd83e01f531
Reviewed-on: https://boringssl-review.googlesource.com/21784
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-27 02:38:45 +00:00
David Benjamin
cba7987978 Revert "Use uint128_t and __asm__ in clang-cl."
This reverts commit f6942f0d22.

Reason for revert: This doesn't actually work in clang-cl. I
forgot we didn't have the clang-cl try bots enabled! :-( I
believe __asm__ is still okay, but I'll try it by hand
tomorrow.

Original change's description:
> Use uint128_t and __asm__ in clang-cl.
> 
> clang-cl does not define __GNUC__ but is still a functioning clang. We
> should be able to use our uint128_t and __asm__ code in it on Windows.
> 
> Change-Id: I67310ee68baa0c0c947b2441c265b019ef12af7e
> Reviewed-on: https://boringssl-review.googlesource.com/22184
> Commit-Queue: Adam Langley <agl@google.com>
> Reviewed-by: Adam Langley <agl@google.com>
> CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

TBR=agl@google.com,davidben@google.com

Change-Id: I5c7e0391cd9c2e8cc0dfde37e174edaf5d17db22
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://boringssl-review.googlesource.com/22224
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-27 00:22:06 +00:00
David Benjamin
f6942f0d22 Use uint128_t and __asm__ in clang-cl.
clang-cl does not define __GNUC__ but is still a functioning clang. We
should be able to use our uint128_t and __asm__ code in it on Windows.

Change-Id: I67310ee68baa0c0c947b2441c265b019ef12af7e
Reviewed-on: https://boringssl-review.googlesource.com/22184
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-27 00:07:29 +00:00
David Benjamin
a37f286f4e Remove the buggy RSA parser.
I've left EVP_set_buggy_rsa_parser as a no-op stub for now, but it
shouldn't need to last very long. (Just waiting for a CL to land in a
consumer.)

Bug: chromium:735616
Change-Id: I6426588f84dd0803661a79c6636a0414f4e98855
Reviewed-on: https://boringssl-review.googlesource.com/22124
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-24 17:39:46 +00:00
David Benjamin
38636aba74 Hide CPU capability symbols in C.
Our assembly does not use the GOT to reference symbols, which means
references to visible symbols will often require a TEXTREL. This is
undesirable, so all assembly-referenced symbols should be hidden. CPU
capabilities are the only such symbols defined in C.

These symbols may be hidden by doing at least one of:

1. Build with -fvisibility=hidden
2. __attribute__((visibility("hidden"))) in C.
3. .extern + .hidden in some assembly file referencing the symbol.

We have lots of consumers and can't always rely on (1) happening. We
were doing (3) by way of d216b71f90 and
16e38b2b8f, but missed 32-bit x86 because
it doesn't cause a linker error.

Those two patches are not in upstream. Upstream instead does (3) by way
of x86cpuid.pl and friends, but we have none of these files.

Standardize on doing (2). This avoids accidentally getting TEXTRELs on
some 32-bit x86 build configurations.  This also undoes
d216b71f90 and
16e38b2b8f. They are no now longer needed
and reduce the upstream diff.

Change-Id: Ib51c43fce6a7d8292533635e5d85d3c197a93644
Reviewed-on: https://boringssl-review.googlesource.com/22064
Commit-Queue: Matt Braithwaite <mab@google.com>
Reviewed-by: Matt Braithwaite <mab@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-10-23 18:36:49 +00:00
Vincent Batts
60931e2d8a Explicit fallthrough on switch
Fixes failed compile with [-Werror=implicit-fallthrough=], which is
default on gcc-7.x on distributions like fedora.

Enabling no implicit fallthrough for more than just clang as well to
catch this going forward.

Change-Id: I6cd880dac70ec126bd7812e2d9e5ff804d32cadd
Signed-off-by: Vincent Batts <vbatts@redhat.com>
Reviewed-on: https://boringssl-review.googlesource.com/20564
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
2017-09-20 19:58:25 +00:00
Martin Kreichgauer
6dc892fcdf Remove redundant calls to |OPENSSL_cleanse| and |OPENSSL_realloc_clean|.
Change-Id: I5c85c4d072ec157b37ed95b284a26ab32c0c42d9
Reviewed-on: https://boringssl-review.googlesource.com/19824
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-09-18 19:16:51 +00:00
David Benjamin
7cc3f4fce0 Use __asm__ instead of asm.
One less macro to worry about in bcm.c.

Change-Id: I321084c0d4ed1bec38c541b04f5b3468350c6eaa
Reviewed-on: https://boringssl-review.googlesource.com/19565
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2017-08-18 23:43:11 +00:00