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>
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>
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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
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(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>
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>
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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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
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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>
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>
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
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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
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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
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These were randomly generated.
Change-Id: I532afdaf469e6c80e518dae3a75547ff7cb0948f
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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
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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
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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
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Commit-Queue: David Benjamin <davidben@google.com>
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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
Commit-Queue: David Benjamin <davidben@google.com>
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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>
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
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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
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The point was to remove the silly moduli.
Change-Id: I48c507c9dd1fc46e38e8991ed528b02b8da3dc1d
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Better commit such details to comments before I forget them.
Change-Id: Ie36332235c692f4369413b4340a742b5ad895ce1
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It's doable, but a bit of effort due to the different radix.
Change-Id: Ibfa15c31bb37de930f155ee6d19551a2b6437073
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This reuses wnaf.c's window scheduling, but has access to the tuned
field arithemetic and pre-computed base point table. Unlike wnaf.c, we
do not make the points affine as it's not worth it for a single table.
(We already precomputed the base point table.)
Annoyingly, 32-bit x86 gets slower by a bit, but the other platforms are
faster. My guess is that that the generic code gets to use the
bn_mul_mont assembly and the compiler, faced with the increased 32-bit
register pressure and the extremely register-poor x86, is making
bad decisions on the otherwise P-256-tuned C code. The three platforms
that see much larger gains are significantly more important than 32-bit
x86 at this point, so go with this change.
armv7a (Nexus 5X) before/after [+14.4%]:
Did 2703 ECDSA P-256 verify operations in 5034539us (536.9 ops/sec)
Did 3127 ECDSA P-256 verify operations in 5091379us (614.2 ops/sec)
aarch64 (Nexus 5X) before/after [+9.2%]:
Did 6783 ECDSA P-256 verify operations in 5031324us (1348.2 ops/sec)
Did 7410 ECDSA P-256 verify operations in 5033291us (1472.2 ops/sec)
x86 before/after [-2.7%]:
Did 8961 ECDSA P-256 verify operations in 10075901us (889.3 ops/sec)
Did 8568 ECDSA P-256 verify operations in 10003001us (856.5 ops/sec)
x86_64 before/after [+8.6%]:
Did 29808 ECDSA P-256 verify operations in 10008662us (2978.2 ops/sec)
Did 32528 ECDSA P-256 verify operations in 10057137us (3234.3 ops/sec)
Change-Id: I5fa643149f5bfbbda9533e3008baadfee9979b93
Reviewed-on: https://boringssl-review.googlesource.com/25684
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
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This was done by OpenSSL with the kind permission of Intel. This change
is imported from upstream's commit
dcf6e50f48e6bab92dcd2dacb27fc17c0de34199.
Change-Id: Ie8d3b700cd527a6e8cf66e0728051b2acd8cc6b9
Reviewed-on: https://boringssl-review.googlesource.com/25588
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This syncs up with OpenSSL master as of
50ea9d2b3521467a11559be41dcf05ee05feabd6. The non-license non-spelling
changes are CFI bits, which were added in upstream in
b84460ad3a3e4fcb22efaa0a8365b826f4264ecf.
Change-Id: I42280985f834d5b9133eacafc8ff9dbd2f0ea59a
Reviewed-on: https://boringssl-review.googlesource.com/25704
Reviewed-by: Adam Langley <agl@google.com>
These files are otherwise up-to-date with OpenSSL master as of
50ea9d2b3521467a11559be41dcf05ee05feabd6, modulo a couple of spelling
fixes which I've imported.
I've also reverted the same-line label and instruction patch to
x86_64-mont*.pl. The new delocate parser handles that fine.
Change-Id: Ife35c671a8104c3cc2fb6c5a03127376fccc4402
Reviewed-on: https://boringssl-review.googlesource.com/25644
Reviewed-by: Adam Langley <agl@google.com>
This imports 384e6de4c7e35e37fb3d6fbeb32ddcb5eb0d3d3f and
79ca382d4762c58c4b92fceb4e202e90c71292ae from upstream.
Differences from upstream:
- We've removed a number of unused functions.
- We never imported 3ff08e1dde56747011a702a9a5aae06cfa8ae5fc, which was
to give the assembly control over the memory layout in the tables. So
our "gather" is "select" (which is implemented the same because the
memory layout never did change) and our "scatter" is in C.
Change-Id: I90d4a17da9f5f693f4dc4706887dec15f010071b
Reviewed-on: https://boringssl-review.googlesource.com/25586
Reviewed-by: Adam Langley <agl@google.com>
As of upstream's 6aa36e8e5a062e31543e7796f0351ff9628832ce, the
corresponding file in OpenSSL has both an Intel and OpenSSL copyright
blocks. To properly sync up with OpenSSL, use the OpenSSL copyright
block and our version of the Intel copyright block.
Change-Id: I4dc072a11390a54d0ce38ec0b8893e48f52638de
Reviewed-on: https://boringssl-review.googlesource.com/25585
Reviewed-by: Adam Langley <agl@google.com>
Change-Id: I5fc029ceddfa60b2ccc97c138b94c1826f6d75fa
Reviewed-on: https://boringssl-review.googlesource.com/25844
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OpenSSL's RSA API is poorly designed and does not have a single place to
properly initialize the key. See
https://github.com/openssl/openssl/issues/5158.
To workaround this flaw, we must lazily instantiate pre-computed
Montgomery bits with locking. This is a ton of complexity. More
importantly, it makes it very difficult to implement RSA without side
channels. The correct in-memory representation of d, dmp1, and dmq1
depend on n, p, and q, respectively. (Those values have private
magnitudes and must be sized relative to the respective moduli.)
08805fe279 attempted to fix up the various
widths under lock, when we set up BN_MONT_CTX. However, this introduces
threading issues because other threads may access those exposed
components (RSA_get0_* also count as exposed for these purposes because
they are get0 functions), while a private key operation is in progress.
Instead, we do the following:
- There is no actual need to minimize n, p, and q, but we have minimized
copies in the BN_MONT_CTXs, so use those.
- Store additional copies of d, dmp1, and dmq1, at the cost of more
memory used. These copies have the correct width and are private,
unlike d, dmp1, and dmq1 which are sadly exposed. Fix private key
operations to use them.
- Move the frozen bit out of rsa->flags, as that too was historically
accessible without locking.
(Serialization still uses the original BIGNUMs, but the RSAPrivateKey
serialization format already inherently leaks the magnitude, so this
doesn't matter.)
Change-Id: Ia3a9b0629f8efef23abb30bfed110d247d1db42f
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If a caller is in the process on constructing an arbitrary |EC_GROUP|,
and they try to create an |EC_POINT| to set as the generator which is
invalid, we would previously crash.
Change-Id: Ida91354257a02bd56ac29ba3104c9782b8d70f6b
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This allows a BIGNUM consumer to avoid messing around with bn->d and
bn->top/width.
Bug: 232
Change-Id: I134cf412fef24eb404ff66c84831b4591d921a17
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This is a bit easier to read than BN_less_than_consttime when we must do
>= or <=, about as much work to compute, and lots of code calls BN_cmp
on secret data. This also, by extension, makes BN_cmp_word
constant-time.
BN_equal_consttime is probably a little more efficient and is perfectly
readable, so leave that one around.
Change-Id: Id2e07fe312f01cb6fd10a1306dcbf6397990cf13
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The loop and the outermost special-cases are basically the same.
Change-Id: I5e3ca60ad9a04efa66b479eebf8c3637a11cdceb
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Same mistake as bn_mul_recursive.
Change-Id: I2374d37e5da61c82ccb1ad79da55597fa3f10640
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This follows similar lines as the previous cleanups and fixes the
documentation of the preconditions.
And with that, RSA private key operations, provided p and q have the
same bit length, should be constant time, as far as I know. (Though I'm
sure I've missed something.)
bn_cmp_part_words and bn_cmp_words are no longer used and deleted.
Bug: 234
Change-Id: Iceefa39f57e466c214794c69b335c4d2c81f5577
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The power of two computations here were extremely confusing and one of
the comments mixed && and ||. Remove the cached k = j + j value.
Optimizing the j*8, j*8, j*2, and j*4 multiplications is the compiler's
job. If it doesn't manage it, it was only a couple shifts anyway.
With that fixed, it becomes easier to tell that rr was actaully
allocated twice as large as necessary. I suspect rr is also
incorrectly-allocated in the bn_mul_part_recursive case, but I'll wait
until I've checked that function over first. (The array size
documentation on the other bn_{mul,sqr}_recursive functions have had
mistakes before.)
Change-Id: I298400b988e3bd108d01d6a7c8a5b262ddf81feb
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I left the input length as int because the calling convention passes
these messy deltas around. This micro-optimization is almost certainly
pointless, but bn_sub_part_words is written in assembly, so I've left it
alone for now. The documented preconditions were also all completely
wrong, so I've fixed them. We actually only call them for even tighter
bounds (one of dna or dnb is 0 and the other is 0 or -1), at least
outside bn_mul_part_recursive which I still need to read through.
This leaves bn_mul_part_recursive, which is reachable for RSA keys which
are not a power of two in bit width.
The first iteration of this had an uncaught bug, so I added a few more
aggressive tests generated with:
A = 0x...
B = 0x...
# Chop off 0, 1 and > 1 word for both 32 and 64-bit.
for i in (0, 1, 2, 4):
for j in (0, 1, 2, 4):
a = A >> (32*i)
b = B >> (32*j)
p = a * b
print "Product = %x" % p
print "A = %x" % a
print "B = %x" % b
print
Bug: 234
Change-Id: I72848d992637c0390cdd3c4f81cb919393b59eb8
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We still need BN_mul and, in particular, bn_mul_recursive will either
require bn_abs_sub_words be generalized or that we add a parallel
bn_abs_sub_part_words, but start with the easy one.
While I'm here, simplify the i and j mess in here. It's patterned after
the multiplication one, but can be much simpler.
Bug: 234
Change-Id: If936099d53304f2512262a1cbffb6c28ae30ccee
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There is no more need for the "constant-time" reading beyond bn->top. We
can write the bytes out naively because RSA computations no longer call
bn_correct_top/bn_set_minimal_width.
Specifically, the final computation is a BN_mod_mul_montgomery to remove
the blinding, and that keeps the sizes correct.
Bug: 237
Change-Id: I6e90d81c323b644e179d899f411479ea16deab98
Reviewed-on: https://boringssl-review.googlesource.com/25324
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