Commit Graph

311 Commits

Author SHA1 Message Date
David Benjamin
56ea9e2769 Fix bn_mod_exp_mont_small when exponentiating to zero.
It's defined to return one in Montgomery form, not a normal one.

(Not that this matters. This function is only used to Fermat's Little
Theorem. Probably it should have been less general, though we'd need to
make new test vectors first.)

Change-Id: Ia8d7588e6a413b25f01280af9aacef0192283771
Reviewed-on: https://boringssl-review.googlesource.com/27285
Reviewed-by: Adam Langley <agl@google.com>
2018-04-18 22:13:16 +00:00
David Benjamin
e0ae249f03 Remove a = 0 special-case in BN_mod_exp_mont.
BN_mod_exp_mont is intended to protect the base, but not the exponent.
Accordingly, it shouldn't treat a base of zero as special.

Change-Id: Ib053e8ce65ab1741973a9f9bfeff8c353567439c
Reviewed-on: https://boringssl-review.googlesource.com/27284
Reviewed-by: Adam Langley <agl@google.com>
2018-04-18 22:03:16 +00:00
David Benjamin
d319205007 Deny CRT to unbalanced RSA keys.
Our technique to perform the reduction only works for balanced key
sizes. For unbalanced keys, we fall back to variable-time logic.
Instead, fall back earlier to the non-CRT codepath, which is still
secure, just slower. This also aligns with the advice here:

https://github.com/HACS-workshop/spectre-mitigations/blob/master/crypto_guidelines.md#1-do-not-conditionally-choose-between-constant-and-non-constant-time

Update-Note: This is a performance hit (some keys will run 3x slower),
but only for keys with different-sized primes. I believe the Windows
crypto APIs will not accept such keys at all. There are two scenarios to
be concerned with for RSA performance:

1. Performance of reasonably-generated keys. Keys that BoringSSL or
anyone else reasonable generates will all be balanced, so this change
does not affect them.

2. Worst-case performance for DoS purposes. This CL does not change the
worst-case performance for RSA at a given bit size. In fact, it improves
it slightly. A sufficiently unbalanced RSA key is as slow as not doing
CRT at all.

In both cases, this change does not affect performance. The affected
keys are pathologically-generated ones that were not quite pathological
enough.

Bug: 235
Change-Id: Ie298dabb549ab9108fa9374aa86ebffe8b6c6c88
Reviewed-on: https://boringssl-review.googlesource.com/27504
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2018-04-17 15:14:04 +00:00
Adam Langley
b2eaeb0b8b Drop some trial-division primes for 1024-bit candidates.
This is helpful at smaller sizes because the benefits of an unlikely hit
by trival-division are smaller.

The full set of kPrimes eliminates about 94.3% of random numbers. The
first quarter eliminates about 93.2% of them. But the little extra power
of the full set seems to be borderline for RSA 3072 and clearly positive
for RSA 4096.

Did 316 RSA 2048 key-gen operations in 30035598us (10.5 ops/sec)
  min: 19423us, median: 80448us, max: 394265us

Change-Id: Iee53f721329674ae7a08fabd85b4f645c24e119d
Reviewed-on: https://boringssl-review.googlesource.com/26944
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: David Benjamin <davidben@google.com>
2018-04-05 03:53:01 +00:00
David Benjamin
eda47f5d98 Make generic point arithmetic slightly less variable-time.
The generic code special-cases affine points, but this leaks
information. (Of course, the generic code also doesn't have a
constant-time multiply and other problems, but one thing at a time.)

The optimization in point doubling is not useful. Point multiplication
more-or-less never doubles an affine point. The optimization in point
addition *is* useful because the wNAF code converts the tables to
affine. Accordingly, align with the P-256 code which adds a 'mixed'
parameter.

(I haven't aligned the formally-verified point formulas themselves yet;
initial testing suggests that the large number of temporaries take a
perf hit with BIGNUM. I'll check the results in EC_FELEM, which will be
stack-allocated, to see if we still need to help the compiler out.)

Strangly, it actually got a bit faster with this change. I'm guessing
because now it doesn't need to bother with unnecessary comparisons and
maybe was kinder to the branch predictor?

Before:
Did 2201 ECDH P-384 operations in 3068341us (717.3 ops/sec)
Did 4092 ECDSA P-384 signing operations in 3076981us (1329.9 ops/sec)
Did 3503 ECDSA P-384 verify operations in 3024753us (1158.1 ops/sec)
Did 992 ECDH P-521 operations in 3017884us (328.7 ops/sec)
Did 1798 ECDSA P-521 signing operations in 3059000us (587.8 ops/sec)
Did 1581 ECDSA P-521 verify operations in 3033142us (521.2 ops/sec)

After:
Did 2310 ECDH P-384 operations in 3092648us (746.9 ops/sec)
Did 4080 ECDSA P-384 signing operations in 3044588us (1340.1 ops/sec)
Did 3520 ECDSA P-384 verify operations in 3056070us (1151.8 ops/sec)
Did 992 ECDH P-521 operations in 3012779us (329.3 ops/sec)
Did 1792 ECDSA P-521 signing operations in 3019459us (593.5 ops/sec)
Did 1600 ECDSA P-521 verify operations in 3047749us (525.0 ops/sec)

Bug: 239
Change-Id: If5d13825fc98e4c58bdd1580cf0245bf7ce93a82
Reviewed-on: https://boringssl-review.googlesource.com/27004
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2018-04-04 21:33:22 +00:00
David Benjamin
ba9da449a4 Tolerate a null BN_CTX in BN_primality_test.
This used to work, but I broke it on accident in the recent rewrite.

Change-Id: I06ab5e06eb0c0a6b67ecc97919654e386f3c2198
Reviewed-on: https://boringssl-review.googlesource.com/26984
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Martin Kreichgauer <martinkr@google.com>
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
2018-04-03 18:13:47 +00:00
David Benjamin
5b05988add Implement field_{mul,sqr} in p224-64.c with p224_felems.
This is in preparation for representing field elements with
stack-allocated types in the generic code. While there is likely little
benefit in threading all the turned field arithmetic through all the
generic code, and the P-224 logic, in particular, does not have a tight
enough abstraction for this, the current implementations depend on
BN_div, which is not compatible with stack-allocating things and avoiding
malloc.

This also speeds things up slightly, now that benchmarks cover point
validation.

Before:
Did 82786 ECDH P-224 operations in 10024326us (8258.5 ops/sec)
After:
Did 89991 ECDH P-224 operations in 10012429us (8987.9 ops/sec)

Change-Id: I468483b49f5dc69187aebd62834365ce5caab795
Reviewed-on: https://boringssl-review.googlesource.com/26971
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:27:45 +00:00
David Benjamin
c81ecf3436 Add test coverage for the a != -3 case.
Alas, it is reachable by way of the legacy custom curves API. Add a
basic test to ensure those codepaths work.

Change-Id: If631110045a664001133a0d07fdac4c67971a15f
Reviewed-on: https://boringssl-review.googlesource.com/26970
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:25:08 +00:00
David Benjamin
04018c5929 Remove EC_LOOSE_SCALAR.
ECDSA converts digests to scalars by taking the leftmost n bits, where n
is the number of bits in the group order. This does not necessarily
produce a fully-reduced scalar.

Montgomery multiplication actually tolerates this slightly looser bound,
so we did not bother with the conditional subtraction. However, this
subtraction is free compared to the multiplication, inversion, and base
point multiplication. Simplify things by keeping it fully-reduced.

Change-Id: If49dffefccc21510f40418dc52ea4da7e3ff198f
Reviewed-on: https://boringssl-review.googlesource.com/26968
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:22:58 +00:00
David Benjamin
9c1f8b4ac7 Add tests for large digests.
ECDSA's logic for converting digests to scalars sometimes produces
slightly unreduced values. Test these cases.

Change-Id: I67a5078db684ee82c286f41e71b13b57c3ee707b
Reviewed-on: https://boringssl-review.googlesource.com/26967
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:18:23 +00:00
David Benjamin
2257e8f3bf Use bn_rshift_words for the ECDSA bit-shift.
May as well use it. Also avoid an overflow with digest_len if someone
asks to sign a truly enormous digest.

Change-Id: Ia0a53007a496f9c7cadd44b1020ec2774b310936
Reviewed-on: https://boringssl-review.googlesource.com/26966
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:17:39 +00:00
David Benjamin
0645c05f5e Test the bit-shifting case in ECDSA.
For non-custom curves, this only comes up with P-521 and, even then,
only with excessively large hashes. Still, we should have test coverage
for this.

Change-Id: Id17a6f47d59d6dd4a43a93857fd3df490f9fa965
Reviewed-on: https://boringssl-review.googlesource.com/26965
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:14:27 +00:00
David Benjamin
cbe77925f4 Extract the single-subtraction reduction into a helper function.
We do this in four different places, with the same long comment, and I'm
about to add yet another one.

Change-Id: If28e3f87ea71020d9b07b92e8947f3848473d99d
Reviewed-on: https://boringssl-review.googlesource.com/26964
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:13:45 +00:00
David Benjamin
25f3d84f4c Rewrite BN_rand without an extra malloc.
RSA keygen uses this to pick primes. May as well avoid bouncing on
malloc. (The BIGNUM internally allocates, of course, but that allocation
will be absorbed by BN_CTX in RSA keygen.)

Change-Id: Ie2243a6e48b9c55f777153cbf67ba5c06688c2f1
Reviewed-on: https://boringssl-review.googlesource.com/26887
Reviewed-by: Adam Langley <agl@google.com>
2018-04-02 18:07:12 +00:00
Adam Langley
eb7c3008cc Only do 16 iterations to blind the primality test.
With this, in 0.02% of 1024-bit primes (which is what's used with an RSA
2048 generation), we'll leak that we struggled to generate values less
than the prime. I.e. that there's a greater likelihood of zero bits
after the leading 1 bit in the prime.

But this recovers all the speed loss from making key generation
constant-time, and then some.

Did 273 RSA 2048 key-gen operations in 30023223us (9.1 ops/sec)
  min: 23867us, median: 93688us, max: 421466us
Did 66 RSA 3072 key-gen operations in 30041763us (2.2 ops/sec)
  min: 117044us, median: 402095us, max: 1096538us
Did 31 RSA 4096 key-gen operations in 31673405us (1.0 ops/sec)
  min: 245109us, median: 769480us, max: 2659386us

Change-Id: Id82dedde35f5fbb36b278189c0685a13c7824590
Reviewed-on: https://boringssl-review.googlesource.com/26924
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 22:31:36 +00:00
David Benjamin
5833dd807e Limit the public exponent in RSA_generate_key_ex.
Windows CryptoAPI and Go bound public exponents at 2^32-1, so don't
generate keys which would violate that.

https://github.com/golang/go/issues/3161
https://msdn.microsoft.com/en-us/library/aa387685(VS.85).aspx

BoringSSL itself also enforces a 33-bit limit.

I don't currently have plans to take much advantage of it, but the
modular inverse step and one of the GCDs in RSA key generation are
helped by small public exponents[0]. In case someone feels inspired
later, get this limit enforced now. Use 32-bits as that's a more
convenient limit, and there's no requirement to produce e=2^32+1 keys.
(Is there still a requirement to accept them?)

[0] This isn't too bad, but it's only worth it if it produces simpler or
smaller code. RSA keygen is not performance-critical.

1. Make bn_mod_u16_consttime work for uint32_t. It only barely doesn't
   work. Maybe only accept 3 and 65537 and pre-compute, maybe call into
   bn_div_rem_words and friends, maybe just tighten the bound a hair
   longer.
2. Implement bn_div_u32_consttime by incorporating 32-bit chunks much
   like bn_mod_u32_consttime.
3. Perform one normal Euclidean algorithm iteration rather than using the
   binary version. u, v, B, and D are now single words, while A and C
   are full-width.
4. Continue with binary Euclidean algorithm (u and v are still secret),
   taking advantage of most values being small.

Update-Note: RSA_generate_key_ex will no longer generate keys with
   public exponents larger than 2^32-1. Everyone uses 65537, save some
   folks who use 3, so this shouldn't matter.

Change-Id: I0d28a29a30d9ff73bff282e34dd98e2b64c35c79
Reviewed-on: https://boringssl-review.googlesource.com/26365
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:54:18 +00:00
David Benjamin
c1c6eeb5e2 Check d is mostly-reduced in RSA_check_key.
We don't check it is fully reduced because different implementations use
Carmichael vs Euler totients, but if d exceeds n, something is wrong.
Note the fixed-width BIGNUM changes already fail operations with
oversized d.

Update-Note: Some blatantly invalid RSA private keys will be rejected at
    RSA_check_key time. Note that most of those keys already are not
    usable with BoringSSL anyway. This CL moves the failure from
    sign/decrypt to RSA_check_key.

Change-Id: I468dbba74a148aa58c5994cc27f549e7ae1486a2
Reviewed-on: https://boringssl-review.googlesource.com/26374
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:54:10 +00:00
David Benjamin
cba958f406 Make RSA_check_key constant-time and more meaningful.
Rather than recompute values the same as in key generation, where
possible, we check differently. In particular, most RSA values are
modular inverses of some value. Check each of them by multiplying and
using our naive constant-time division function.

Median of 29 RSA keygens: 0m0.218s -> 0m0.205s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: Iaca19f12c045457013def844a17bf502ed09136e
Reviewed-on: https://boringssl-review.googlesource.com/26373
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:54:00 +00:00
David Benjamin
c4e4757b63 Make RSA key generation constant-time.
This leaves RSA_check_key, which will be fixed in subsequent commits.

Median of 29 RSA keygens: 0m0.220s -> 0m0.209s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I325f23fcc59302e68570908e5427b65471b799f6
Reviewed-on: https://boringssl-review.googlesource.com/26371
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:53:52 +00:00
David Benjamin
a44dae7fd3 Add a constant-time generic modular inverse function.
This uses the full binary GCD algorithm, where all four of A, B, C, and
D must be retained. (BN_mod_inverse_odd implements the odd number
version which only needs A and C.) It is patterned after the version
in the Handbook of Applied Cryptography, but tweaked so the coefficients
are non-negative and bounded.

Median of 29 RSA keygens: 0m0.225s -> 0m0.220s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I6dc13524ea7c8ac1072592857880ddf141d87526
Reviewed-on: https://boringssl-review.googlesource.com/26370
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:53:44 +00:00
David Benjamin
1044553d6d Add new GCD and related primitives.
RSA key generation requires computing a GCD (p-1 and q-1 are relatively
prime with e) and an LCM (the Carmichael totient). I haven't made BN_gcd
itself constant-time here to save having to implement
bn_lshift_secret_shift, since the two necessary operations can be served
by bn_rshift_secret_shift, already added for Rabin-Miller. However, the
guts of BN_gcd are replaced. Otherwise, the new functions are only
connected to tests for now, they'll be used in subsequent CLs.

To support LCM, there is also now a constant-time division function.
This does not replace BN_div because bn_div_consttime is some 40x slower
than BN_div. That penalty is fine for RSA keygen because that operation
is not bottlenecked on division, so we prefer simplicity over
performance.

Median of 29 RSA keygens: 0m0.212s -> 0m0.225s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: Idbfbfa6e7f5a3b8782ce227fa130417b3702cf97
Reviewed-on: https://boringssl-review.googlesource.com/26369
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:53:36 +00:00
David Benjamin
23af438ccd Compute p - q in constant time.
Expose the constant-time abs_sub functions from the fixed Karatsuba code
in BIGNUM form for RSA to call into. RSA key generation involves
checking if |p - q| is above some lower bound.

BN_sub internally branches on which of p or q is bigger. For any given
iteration, this is not secret---one of p or q is necessarily the larger,
and whether we happened to pick the larger or smaller first is
irrelevant. Accordingly, there is no need to perform the p/q swap at the
end in constant-time.

However, this stage of the algorithm picks p first, sticks with it, and
then computes |p - q| for various q candidates. The distribution of
comparisons leaks information about p. The leak is unlikely to be
problematic, but plug it anyway.

Median of 29 RSA keygens: 0m0.210s -> 0m0.212s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I024b4e51b364f5ca2bcb419a0393e7be13249aec
Reviewed-on: https://boringssl-review.googlesource.com/26368
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:53:28 +00:00
David Benjamin
8d9ee7d1fe Replace rsa_greater_than_pow2 with BN_cmp.
It costs us a malloc, but it's one less function to test and implement
in constant time, now that BN_cmp and BIGNUM are okay.

Median of 29 RSA keygens: 0m0.207s -> 0m0.210s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: Ic56f92f0dcf04da1f542290a7e8cdab8036699ed
Reviewed-on: https://boringssl-review.googlesource.com/26367
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:53:18 +00:00
David Benjamin
97ac45e2f7 Change the order of GCD and trial division.
RSA key generation currently does the GCD check before the primality
test, in hopes of discarding things invalid by other means before
running the expensive primality check.

However, GCD is about to get a bit more expensive to clear the timing
leak, and the trial division part of primality testing is quite fast.
Thus, split that portion out via a new bn_is_obviously_composite and
call it before GCD.

Median of 29 RSA keygens: 0m0.252s -> 0m0.207s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I3999771fb73cca16797cab9332d14c4ebeb02046
Reviewed-on: https://boringssl-review.googlesource.com/26366
Reviewed-by: Adam Langley <alangley@gmail.com>
2018-03-30 19:53:06 +00:00
David Benjamin
56f5eb9ffd Name constant-time functions more consistently.
I'm not sure why I separated "fixed" and "quick_ctx" names. That's
annoying and doesn't generalize well to, say, adding a bn_div_consttime
function for RSA keygen.

Change-Id: I751d52b30e079de2f0d37a952de380fbf2c1e6b7
Reviewed-on: https://boringssl-review.googlesource.com/26364
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>
2018-03-29 23:30:55 +00:00
David Benjamin
e6f46e2563 Blind the range check for finding a Rabin-Miller witness.
Rabin-Miller requires selecting a random number from 2 to |w|-1.
This is done by picking an N-bit number and discarding out-of-range
values. This leaks information about |w|, so apply blinding. Rather than
discard bad values, adjust them to be in range.
Though not uniformly selected, these adjusted values
are still usable as Rabin-Miller checks.

Rabin-Miller is already probabilistic, so we could reach the desired
confidence levels by just suitably increasing the iteration count.
However, to align with FIPS 186-4, we use a more pessimal analysis: we
do not count the non-uniform values towards the iteration count. As a
result, this function is more complex and has more timing risk than
necessary.

We count both total iterations and uniform ones and iterate until we've
reached at least |BN_PRIME_CHECKS_BLINDED| and |iterations|,
respectively.  If the latter is large enough, it will be the limiting
factor with high probability and we won't leak information.

Note this blinding does not impact most calls when picking primes
because composites are rejected early. Only the two secret primes see
extra work.  So while this does make the BNTest.PrimeChecking test take
about 2x longer to run on debug mode, RSA key generation time is fine.

Another, perhaps simpler, option here would have to run
bn_rand_range_words to the full 100 count, select an arbitrary
successful try, and declare failure of the entire keygen process (as we
do already) if all tries failed. I went with the option in this CL
because I happened to come up with it first, and because the failure
probability decreases much faster. Additionally, the option in this CL
does not affect composite numbers, while the alternate would. This gives
a smaller multiplier on our entropy draw. We also continue to use the
"wasted" work for stronger assurance on primality. FIPS' numbers are
remarkably low, considering the increase has negligible cost.

Thanks to Nathan Benjamin for helping me explore the failure rate as the
target count and blinding count change.

Now we're down to the rest of RSA keygen, which will require all the
operations we've traditionally just avoided in constant-time code!

Median of 29 RSA keygens: 0m0.169s -> 0m0.298s
(Accuracy beyond 0.1s is questionable. The runs at subsequent test- and
rename-only CLs were 0m0.217s, 0m0.245s, 0m0.244s, 0m0.247s.)

Bug: 238
Change-Id: Id6406c3020f2585b86946eb17df64ac42f30ebab
Reviewed-on: https://boringssl-review.googlesource.com/25890
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
2018-03-29 22:02:24 +00:00
David Benjamin
8eadca50a2 Don't leak |a| in the primality test.
(This is actually slightly silly as |a|'s probability distribution falls
off exponentially, but it's easy enough to do right.)

Instead, we run the loop to the end. This is still performant because we
can, as before, return early on composite numbers. Only two calls
actually run to the end. Moreover, running to the end has comparable
cost to BN_mod_exp_mont_consttime.

Median time goes from 0.140s to 0.231s. That cost some, but we're still
faster than the original implementation.

We're down to one more leak, which is that the BN_rand_range_ex call
does not hide |w1|. That one may only be solved probabilistically...

Median of 29 RSA keygens: 0m0.123s -> 0m0.145s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I4847cb0053118c572d2dd5f855388b5199fa6ce2
Reviewed-on: https://boringssl-review.googlesource.com/25888
Reviewed-by: Adam Langley <agl@google.com>
2018-03-28 01:44:31 +00:00
David Benjamin
9362ed9e14 Use a Barrett reduction variant for trial division.
Compilers use a variant of Barrett reduction to divide by constants,
which conveniently also avoids problematic operations on the secret
numerator. Implement the variant as described here:
http://ridiculousfish.com/blog/posts/labor-of-division-episode-i.html

Repurpose this to implement a constant-time BN_mod_word replacement.
It's even much faster! I've gone ahead and replaced the other
BN_mod_word calls on the primes table.

That should give plenty of budget for the other changes. (I am assuming
that a regression is okay, as RSA keygen is not performance-sensitive,
but that I should avoid anything too dramatic.)

Proof of correctness: https://github.com/davidben/fiat-crypto/blob/barrett/src/Arithmetic/BarrettReduction/RidiculousFish.v

Median of 29 RSA keygens: 0m0.621s -> 0m0.123s
(Accuracy beyond 0.1s is questionable, though this particular
improvement is quite solid.)

Bug: 238
Change-Id: I67fa36ffe522365b13feb503c687b20d91e72932
Reviewed-on: https://boringssl-review.googlesource.com/25887
Reviewed-by: Adam Langley <agl@google.com>
2018-03-28 01:42:18 +00:00
David Benjamin
232a6be6f1 Make primality testing mostly constant-time.
The extra details in Enhanced Rabin-Miller are only used in
RSA_check_key_fips, on the public RSA modulus, which the static linker
will drop in most of our consumers anyway. Implement normal Rabin-Miller
for RSA keygen and use Montgomery reduction so it runs in constant-time.

Note that we only need to avoid leaking information about the input if
it's a large prime. If the number ends up composite, or we find it in
our table of small primes, we can return immediately.

The leaks not addressed by this CL are:

- The difficulty of selecting |b| leaks information about |w|.
- The distribution of whether step 4.4 runs leaks information about w.
- We leak |a| (the largest power of two which divides w) everywhere.
- BN_mod_word in the trial division is not constant-time.

These will be resolved in follow-up changes.

Median of 29 RSA keygens: 0m0.521 -> 0m0.621s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I0cf0ff22079732a0a3ababfe352bb4327e95b879
Reviewed-on: https://boringssl-review.googlesource.com/25886
Reviewed-by: Adam Langley <agl@google.com>
2018-03-28 01:42:06 +00:00
David Benjamin
50418afb7f Add some EC base point multiplication test vectors.
Probably worth having actual test vectors for these, rather than
checking our code against itself. Additionally, small negative numbers
have, in the past been valuable test vectors (see long comment in
point_add from OpenSSL's ecp_nistp521.c).

Change-Id: Ia5aa8a80eb5b6d0089c3601c5fec2364e699794d
Reviewed-on: https://boringssl-review.googlesource.com/26848
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
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2018-03-27 23:33:24 +00:00
David Benjamin
718c88c961 Fix a bug in p224-64.c.
p224_felem_neg does not produce an output within the tight bounds
suitable for p224_felem_contract. This was found by inspection of the
code.

This only affects the final y-coordinate output of arbitrary-point
multiplication, so it is a no-op for ECDH and ECDSA.

Change-Id: I1d929458d1f21d02cd8e745d2f0f7040a6bb0627
Reviewed-on: https://boringssl-review.googlesource.com/26847
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
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2018-03-27 18:03:14 +00:00
David Benjamin
0970d397c4 Make various BIGNUM comparisons constant-time.
Primality testing checks for small words in random places.

Median of 29 RSA keygens: 0m0.811s -> 0m0.521s
(Accuracy beyond 0.1s is questionable, and this "speed up" is certainly
noise.)

Bug: 238
Change-Id: Ie5efab7291302a42ac6e283d25da0c094d8577e7
Reviewed-on: https://boringssl-review.googlesource.com/25885
Reviewed-by: Adam Langley <agl@google.com>
2018-03-26 18:53:53 +00:00
David Benjamin
ad066861dd Add bn_usub_fixed.
There are a number of random subtractions in RSA key generation. Add a
fixed-width version.

Median of 29 RSA keygens: 0m0.859s -> 0m0.811s
(Accuracy beyond 0.1s is questionable.)

Bug: 238
Change-Id: I9fa0771b95a438fd7d2635fd77a332146ccc96d9
Reviewed-on: https://boringssl-review.googlesource.com/25884
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
2018-03-26 18:53:43 +00:00
Adam Langley
d89d65ba12 Add utility program for emitting P-256 x86-64 table.
No semantic change: the table is the same as before, but now with less
magic.

Change-Id: I351c2446e9765f25b7dfb901c9e98f12099a325c
Reviewed-on: https://boringssl-review.googlesource.com/26744
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
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2018-03-26 16:28:42 +00:00
David Benjamin
5fca613918 Fix typo in point_add.
Rather than writing the answer into the output, it wrote it into some
awkwardly-named temporaries. Thanks to Daniel Hirche for reporting this
issue!

Bug: chromium:825273
Change-Id: I5def4be045cd1925453c9873218e5449bf25e3f5
Reviewed-on: https://boringssl-review.googlesource.com/26785
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
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2018-03-23 21:12:29 +00:00
David Benjamin
d67e311ce4 Test BN_primality test with OEIS A014233 values .
These are composite numbers whose composite witnesses aren't in the
first however many prime numbers, so deterministically checking small
numbers may not work.

We don't check composite witnesses deterministically but these are
probably decent tests. (Not sure how else to find composites with
scarce witnesses, but these seemed decent candidates.)

Change-Id: I23dcb7ba603a64c1f7d1e9a16942e7c29c76da51
Reviewed-on: https://boringssl-review.googlesource.com/26645
Commit-Queue: Steven Valdez <svaldez@google.com>
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2018-03-22 16:26:37 +00:00
David Benjamin
ee764744e0 Add some BN_mod_inverse tests.
Generated randomly.

Change-Id: I51e6871ffddc4c5954a773db4473e944cb9818ed
Reviewed-on: https://boringssl-review.googlesource.com/26084
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2018-03-20 16:11:45 +00:00
David Benjamin
1bfb5c0f79 Add some tests for BN_gcd.
These were randomly generated.

Change-Id: I532afdaf469e6c80e518dae3a75547ff7cb0948f
Reviewed-on: https://boringssl-review.googlesource.com/26065
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2018-03-20 16:08:56 +00:00
David Benjamin
ac97cc0e51 Fill in missing check_bn_tests.go features.
Change-Id: Ic0421b628212521d673cb7053b0fb278c827ebf5
Reviewed-on: https://boringssl-review.googlesource.com/26064
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2018-03-19 21:41:00 +00:00
David Benjamin
4b6055defb Add better tests for BN_rand.
Change-Id: Iefeeeb12c4a5a12e8dffc6817bb368d68a074cd0
Reviewed-on: https://boringssl-review.googlesource.com/25889
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
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2018-03-19 21:18:45 +00:00
David Benjamin
10bfb89859 Fix 20-year-old typo in BN_mask_bits.
This clearly was supposed to be a return 1. See
https://github.com/openssl/openssl/issues/5537 for details.

(Additionally, now that our BIGNUMs may be non-minimal, this function
violates the rule that BIGNUM functions should not depend on widths. We
should use w >= bn_minimal_width(a) to retain the original behavior. But
the original behavior is nuts, so let's just fix it.)

Update-Note: BN_mask_bits no longer reports failure in some cases. These
    cases were platform-dependent and not useful, and code search confirms
    nothing was relying on it.

Change-Id: I31b1c2de6c5de9432c17ec3c714a5626594ee03c
Reviewed-on: https://boringssl-review.googlesource.com/26464
Commit-Queue: Steven Valdez <svaldez@google.com>
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2018-03-08 21:53:06 +00:00
David Benjamin
a6bfc45b62 Store EC_KEY's private key as an EC_SCALAR.
This isn't strictly necessary now that BIGNUMs are safe, but we get to
rely on type-system annotations from EC_SCALAR. Additionally,
EC_POINT_mul depends on BN_div, while the EC_SCALAR version does not.

Change-Id: I75e6967f3d35aef17278b94862f4e506baff5c23
Reviewed-on: https://boringssl-review.googlesource.com/26424
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
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2018-03-07 21:17:31 +00:00
David Benjamin
d62fe6f3e8 Fold EC_KEY_copy into EC_KEY_dup.
EC_KEY_copy left unset fields alone, which meant it was possible to
create an EC_KEY with mismatched private key and group. Nothing was
using EC_KEY_copy anyway, and in keeping of us generally preferring
fresh objects over object reuse, remove it. EC_KEY_dup itself can also
be made simpler by using the very setters available.

Additionally, skip copying the method table. As of
https://boringssl-review.googlesource.com/16344, we no longer copy the
ex_data, so we probably shouldn't copy the method pointers either,
aligning with RSAPrivateKey_dup.

Update-Note: If I missed anything and someone uses EC_KEY_copy, it
   should be easy to port them to EC_KEY_dup.

Change-Id: Ibbdcea73345d91fa143fbe70a15bb527972693e8
Reviewed-on: https://boringssl-review.googlesource.com/26404
Reviewed-by: Steven Valdez <svaldez@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
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2018-03-07 21:17:02 +00:00
David Benjamin
929a9d7d42 Don't bother retrying in bn_blinding_create_param.
The probability of stumbling on a non-invertible b->A is negligible;
it's equivalent to accidentally factoring the RSA key. Relatedly,
document the slight caveat in BN_mod_inverse_blinded.

Change-Id: I308d17d12f5d6a12c444dda8c8fcc175ef2f5d45
Reviewed-on: https://boringssl-review.googlesource.com/26344
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Reviewed-by: Adam Langley <agl@google.com>
2018-03-05 20:48:41 +00:00
Adam Langley
c01786403f Update link to CMVP certificate.
NIST redid their website and broke all the old links.

Change-Id: I5b7cba878404bb63e49f221f6203c8e1e6545af4
Reviewed-on: https://boringssl-review.googlesource.com/26204
Reviewed-by: Adam Langley <agl@google.com>
2018-02-26 22:14:35 +00:00
David Benjamin
672f6fc248 Always use adr with __thumb2__.
Thumb2 addresses are a bit a mess, depending on whether a label is
interpreted as a function pointer value (for use with BX and BLX) or as
a program counter value (for use with PC-relative addressing). Clang's
integrated assembler mis-assembles this code. See
https://crbug.com/124610#c54 for details.

Instead, use the ADR pseudo-instruction which has clear semantics and
should be supported by every assembler that handles the OpenSSL Thumb2
code. (In other files, the ADR vs SUB conditionals are based on
__thumb2__ already. For some reason, this one is based on __APPLE__, I'm
guessing to deal with an older version of clang assembler.)

It's unclear to me which of clang or binutils is "correct" or if this is
even a well-defined notion beyond "whatever binutils does". But I will
note that https://github.com/openssl/openssl/pull/4669 suggests binutils
has also changed behavior around this before.

See also https://github.com/openssl/openssl/pull/5431 in OpenSSL.

Bug: chromium:124610
Change-Id: I5e7a0c8c0f54a3f65cc324ad599a41883675f368
Reviewed-on: https://boringssl-review.googlesource.com/26164
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>
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2018-02-22 22:28:15 +00:00
Daniel Hirche
36714fc8ee Remove redundant length-check in |ec_wNAF_mul|.
Right now, |g_wNAF| and |p_wNAF| are of same size.

This change makes GCC's "-Werror=logical-op" happy and adds a compile-time
assertion in case the initial size of either array ever changes.

Change-Id: I29e39a7a121a0a9d016c53da6b7c25675ddecbdc
Reviewed-on: https://boringssl-review.googlesource.com/26104
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
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2018-02-21 17:03:14 +00:00
David Benjamin
085955c567 Actually use the u64 cast.
The point was to remove the silly moduli.

Change-Id: I48c507c9dd1fc46e38e8991ed528b02b8da3dc1d
Reviewed-on: https://boringssl-review.googlesource.com/26044
Commit-Queue: Steven Valdez <svaldez@google.com>
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2018-02-16 20:02:56 +00:00
Steven Valdez
f16cd4278f Add AES_128_CCM AEAD.
Change-Id: I830be64209deada0f24c3b6d50dc86155085c377
Reviewed-on: https://boringssl-review.googlesource.com/25904
Commit-Queue: Steven Valdez <svaldez@google.com>
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2018-02-16 15:57:27 +00:00
David Benjamin
78a832d793 Document RSAZ slightly better.
Better commit such details to comments before I forget them.

Change-Id: Ie36332235c692f4369413b4340a742b5ad895ce1
Reviewed-on: https://boringssl-review.googlesource.com/25984
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2018-02-15 18:14:04 +00:00