Better commit such details to comments before I forget them.
Change-Id: Ie36332235c692f4369413b4340a742b5ad895ce1
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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
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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
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Change-Id: I5fc029ceddfa60b2ccc97c138b94c1826f6d75fa
Reviewed-on: https://boringssl-review.googlesource.com/25844
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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
Reviewed-on: https://boringssl-review.googlesource.com/25484
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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
Reviewed-on: https://boringssl-review.googlesource.com/25404
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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
Reviewed-on: https://boringssl-review.googlesource.com/25344
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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
Reviewed-on: https://boringssl-review.googlesource.com/25325
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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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This is to be used in constant-time RSA CRT.
Bug: 233
Change-Id: Ibade5792324dc6aba38cab6971d255d41fb5eb91
Reviewed-on: https://boringssl-review.googlesource.com/25286
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Use the now constant-time modular arithmetic functions.
Bug: 236
Change-Id: I4567d67bfe62ca82ec295f2233d1a6c9b131e5d2
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As the EC code will ultimately want to use these in "words" form by way
of EC_FELEM, and because it's much easier, I've implement these as
low-level words-based functions that require all inputs have the same
width. The BIGNUM versions which RSA and, for now, EC calls are
implemented on top of that.
Unfortunately, doing such things in constant-time and accounting for
undersized inputs requires some scratch space, and these functions don't
take BN_CTX. So I've added internal bn_mod_*_quick_ctx functions that
take a BN_CTX and the old functions now allocate a bit unnecessarily.
RSA only needs lshift (for BN_MONT_CTX) and sub (for CRT), but the
generic EC code wants add as well.
The generic EC code isn't even remotely constant-time, and I hope to
ultimately use stack-allocated EC_FELEMs, so I've made the actual
implementations here implemented in "words", which is much simpler
anyway due to not having to take care of widths.
I've also gone ahead and switched the EC code to these functions,
largely as a test of their performance (an earlier iteration made the EC
code noticeably slower). These operations are otherwise not
performance-critical in RSA.
The conversion from BIGNUM to BIGNUM+BN_CTX should be dropped by the
static linker already, and the unused BIGNUM+BN_CTX functions will fall
off when EC_FELEM happens.
Update-Note: BN_mod_*_quick bounce on malloc a bit now, but they're not
really used externally. The one caller I found was wpa_supplicant
which bounces on malloc already. They appear to be implementing
compressed coordinates by hand? We may be able to convince them to
call EC_POINT_set_compressed_coordinates_GFp.
Bug: 233, 236
Change-Id: I2bf361e9c089e0211b97d95523dbc06f1168e12b
Reviewed-on: https://boringssl-review.googlesource.com/25261
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The fallback functions still themselves leak, but I've left TODOs there.
This only affects BN_mod_mul_montgomery on platforms where we don't use
the bn_mul_mont assembly, but BN_mul additionally affects the final
multiplication in RSA CRT.
Bug: 232
Change-Id: Ia1ae16162c38e10c056b76d6b2afbed67f1a5e16
Reviewed-on: https://boringssl-review.googlesource.com/25260
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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
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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
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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
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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
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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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
(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
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(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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
