These are connection state, so they should be reset on SSL_clear.
Change-Id: I861fe52578836615d2719c9e1ff0911c798f336e
Reviewed-on: https://boringssl-review.googlesource.com/27384
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Conscrypt need this function right now. They ought to be fixed up to not
need this but, in the meantime, this API is also provided by OpenSSL and
will clear one most consumer reaching into SSL_SESSION.
Bumping the API since Conscrypt often involves multi-sided stuff.
Change-Id: I665ca6b6a17ef479133c29c23fc639f278128c69
Reviewed-on: https://boringssl-review.googlesource.com/27405
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In addition, make use of bssl::ScopedEVP_MD_CTX in |SpeedHashChunk|,
otherwise the ctx doesn't get destroyed on failure.
Change-Id: I5828080cb9f4eb7c77cc2ff185d9aa8135311385
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OpenSSL 1.1.0 renamed that. Also clang-format wanted to smush it all
onto one line.
Change-Id: Icdaa0eefc503c4aab1b309ccb34625f5e811c537
Reviewed-on: https://boringssl-review.googlesource.com/27404
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Change-Id: Iceed87c194201d28c4a51b1c19a59fe2f20b6a5e
Reviewed-on: https://boringssl-review.googlesource.com/27444
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In the handoff+handback case, bssl_shim.cc creates 3 |SSL| objects:
one to receive the ClientHello, one to receive the handoff, and a
third one to receive the handback.
Before 56986f9, only the first of these received any configuration.
Since that commit, all 3 of them receive the same configuration. That
means that the handback message no longer needs to serialize as many
things.
N.B. even before 56986f9, not all of the fields were necessary. For
example, there was no reason to serialize |conf_max_version| and
|conf_min_version| in the handback, so far as I can tell.
This commit is mechanical: it simply removes everything that doesn't
cause any tests to fail. In the long run, I'll need to carefully
check for two possibilities:
- Knobs that affect the handshake after the server's first message it
sent. These are troublesome because that portion of the handshake
may run on a different |SSL|, depending on whether the handback is
early or late.
- Getters that may be called post-handshake, and that callers may
reasonably expect to reflect the value that was used during
handshake.
(I'm not sure that either case exists!)
Change-Id: Ibf6e0be6609ad6e83ab50e69199e9b2d51e59a87
Reviewed-on: https://boringssl-review.googlesource.com/27364
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(Found by fuzzing: a zero value causes an infinite loop.)
Change-Id: I984fd88d85fb87616b5e806795c10334f4379744
Reviewed-on: https://boringssl-review.googlesource.com/27345
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This separates the source lists for the crypto and ssl targets from
their headers, so the header files can be listed in the 'public'
section of the targets. This allows tighter GN checking and expresses
the build structure more cleanly.
Change-Id: Ifb20c90977d7e858734654d9a03949be19a9c43a
Reviewed-on: https://boringssl-review.googlesource.com/27344
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The last-minute TLS 1.3 change was done partly for consistency with DTLS
1.3, where authenticating the record header is less obviously pointless
than in TLS. There, reconstructing it would be messy. Instead, pass in
the record header and let SSLAEADContext decide whether or not to
assemble its own.
(While I'm here, reorder all the flags so the AD and nonce ones are
grouped together.)
Change-Id: I06e65d526b21a08019e5ca6f1b7c7e0e579e7760
Reviewed-on: https://boringssl-review.googlesource.com/27024
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https://boringssl-review.googlesource.com/10522 didn't actually do what
it was supposed to do. In fact, it appears, not paying attention to it,
we've managed to make RSA verify slower than ECDSA verify. Oops.
Did 32000 RSA 2048 verify (same key) operations in 1016746us (31473.0 ops/sec)
Did 5525 RSA 2048 verify (fresh key) operations in 1067209us (5177.1 ops/sec)
Did 8957 ECDSA P-256 verify operations in 1078570us (8304.5 ops/sec)
The difference is in setting up the BN_MONT_CTX, either computing R^2 or n0.
I'm guessing R^2. The current algorithm needs to be constant-time, but we can
split out a variable-time one if necessary.
Change-Id: Ie064a0e464aaa803815b56a6734bc9e2becef1a7
Reviewed-on: https://boringssl-review.googlesource.com/27244
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If we don't have OID data for an object then we should fail if we
are asked to encode the ASN.1 for that OID.
(Imported from upstream's f3f8e72f494b36d05e0d04fe418f92b692fbb261.)
Change-Id: I3c3d3a3b236bca374fde3c0d02504140f2992602
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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
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Reviewed-by: David Benjamin <davidben@google.com>
Change-Id: I7298c878bd2c8187dbd25903e397e8f0c2575aa4
Reviewed-on: https://boringssl-review.googlesource.com/26846
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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
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This changes the contract for split handshakes such that on the
receiving side, the connection is to be driven until it returns
|SSL_ERROR_HANDBACK|, rather than until SSL_do_handshake() returns
success.
Change-Id: Idd1ebfbd943d88474d7c934f4c0ae757ff3c0f37
Reviewed-on: https://boringssl-review.googlesource.com/26864
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Reviewed-by: Adam Langley <agl@google.com>
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>
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The relevant result (Damgård, Landrock, and Pomerance, Average Case
Error Estimates for the Strong Probably Prime Test) is only applicable
for randomly selected candidates. It relies on there being very few odd
composites with many false witnesses.
(If testing an adversarially-selected composite, false witnesses are
bounded by ϕ(n)/4 for n != 9, so one needs about 40 iterations for a
2^-80 false positive rate.)
Change-Id: I2a063dac5f9042dcb9e6affee8d2ae575f2238a9
Reviewed-on: https://boringssl-review.googlesource.com/26972
Reviewed-by: Adam Langley <agl@google.com>
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>
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>
This includes a point validation, which figures into the overall cost of
an ECDH operation. If, say, point validation is slow because it uses
generic code, we'd like it to show up in benchmarks.
(Later I'd like to replace this mess with a simple byte-oriented ECDH
API. When that happens, I'll update the benchmark accordingly.)
Change-Id: If8c33542d4b40572aac0a71ea2f658e7bc501f4b
Reviewed-on: https://boringssl-review.googlesource.com/26969
Reviewed-by: Adam Langley <agl@google.com>
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>
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>
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>
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>
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>
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>
AUTHORITY_INFO_ACCESS is a STACK_OF(ACCESS_DESCRIPTION), so we want to
add a deleter for ACCESS_DESCRIPTION, at which point
AUTHORITY_INFO_ACCESS's deleter will show up for free.
Change-Id: Id9efb74093868c39a893de67dd26f1fc15379252
Reviewed-on: https://boringssl-review.googlesource.com/26973
Reviewed-by: Ryan Sleevi <rsleevi@chromium.org>
Reviewed-by: David Benjamin <davidben@google.com>
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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>
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/3161https://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>
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>
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>
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>
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>
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>
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>
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>
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>
This reverts commit 21ef155063. Doesn't
look like I succeeded in uploading that. Will sort that out later.
Change-Id: Ic5395abe46b2b99aaffd254afcd97157518c8ba8
Reviewed-on: https://boringssl-review.googlesource.com/26886
Reviewed-by: David Benjamin <davidben@google.com>
This change follows up from e759a9cd with more extensive changes and
tests:
If a name checking function (like |X509_VERIFY_PARAM_set1_host|) fails,
it now poisons the |X509_VERIFY_PARAM| so that all verifications will
fail. This is because we have observed that some callers are not
checking the return value of these functions.
Using a length of zero for a hostname to mean |strlen| is now an error.
It also an error for email addresses and IP addresses now, and doesn't
end up trying to call |strlen| on a (binary) IP address.
Setting an email address with embedded NULs now fails. So does trying to
configure an empty hostname or email with (NULL, 0).
|X509_check_*| functions in BoringSSL don't accept zero lengths (unlike
OpenSSL). It's now tested that such calls always fail.
Change-Id: I4484176f2aae74e502a09081c7e912c85e8d090b
Update-Note: several behaviour changes. See change description.
Reviewed-on: https://boringssl-review.googlesource.com/26764
Reviewed-by: David Benjamin <davidben@google.com>
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>
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>
(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>
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>
David Benjamin
Daniel Hirche
Steven Valdez
Matthew Braithwaite
James Robinson
Adam Langley
Adam Langley