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Use a mix of bsaes and vpaes for CTR on NEON.

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tl;dr: AES is now constant-time on 32-bit ARM with NEON. Combined with
all the past work, we now have constant-time AES and GHASH on ARM and
x86 chips, 32-bit and 64-bit, provided NEON (required by Chrome on
Android, aside from https://crbug.com/341598) or SSSE3 (almost all
Chrome on Windows users) is available!

CTR-like bsaes modes is harder to resolve than CBC decryption. They use
both bulk (ctr128_f) and one-off (block128_f) operations. We currently
use ctr128_f of bsaes and block128_f of aes_nohw (not constant-time),
which hits 22.0 MB/s on my test chip.

Implement a vpaes/bsaes hybrid to get the best of both worlds. The key
is kept in vpaes form and, when the input is large enough, we convert
the key to bsaes on-demand. This retains bsaes performance, but with no
variable-time gaps.

Alternatives considered:

- Convert to bsaes form immediately and only use bsaes. This makes the
  one-off block128_f calls very expensive. One 8-block batch of
  bsaes_ctr32_encrypt_blocks costs as much as 5.76 vpaes_encrypt calls.

- Do the above, but fold the one-off calls into bsaes batches because
  GCM is parallelizable. This is a mess with the current internal
  structure and doesn't apply to, e.g., CCM.

- Drop bsaes in favor of vpaes. However, even with
  vpaes_ctr32_encrypt_blocks, vpaes is 15.5 MB/s. The hybrid is a 40%
  win on an important platform.

- Try to narrow the gap, as we did for x86_64, with a "2x" optimization.
  I attempted this here but the register pressure was tricky. (x86_64
  was already tight and NEON can't address memory in vtbl.) If I ignored
  this (gives wrong answer), the gap was still 20-25%. Perf here is
  slower overall (20 MB/s for old ARM vs 120-140 MB/s for old x86_64),
  so that gap is scarier.

I retained vpaes_ctr32_encrypt_blocks because it's fairly compact (only
84 bytes assembled), though it's less important in the bsaes hybrid.

Cortex-A53 (Raspberry Pi 3 Model B+)
Before:
Did 267000 AES-128-GCM (16 bytes) seal operations in 2004871us (133175.7 ops/sec): 2.1 MB/s
Did 135000 AES-128-GCM (256 bytes) seal operations in 2013825us (67036.6 ops/sec): 17.2 MB/s
Did 31000 AES-128-GCM (1350 bytes) seal operations in 2059039us (15055.6 ops/sec): 20.3 MB/s
Did 5565 AES-128-GCM (8192 bytes) seal operations in 2073607us (2683.7 ops/sec): 22.0 MB/s
Did 2709 AES-128-GCM (16384 bytes) seal operations in 2020264us (1340.9 ops/sec): 22.0 MB/s
Did 209000 AES-256-GCM (16 bytes) seal operations in 2005654us (104205.4 ops/sec): 1.7 MB/s
Did 109000 AES-256-GCM (256 bytes) seal operations in 2011293us (54194.0 ops/sec): 13.9 MB/s
Did 25000 AES-256-GCM (1350 bytes) seal operations in 2082385us (12005.5 ops/sec): 16.2 MB/s
Did 4452 AES-256-GCM (8192 bytes) seal operations in 2080729us (2139.6 ops/sec): 17.5 MB/s
Did 2226 AES-256-GCM (16384 bytes) seal operations in 2079819us (1070.3 ops/sec): 17.5 MB/s

After:
Did 542000 AES-128-GCM (16 bytes) seal operations in 2003408us (270539.0 ops/sec): 4.3 MB/s [+104.8%]
Did 124000 AES-128-GCM (256 bytes) seal operations in 2012579us (61612.5 ops/sec): 15.8 MB/s [-8.1%]
Did 30000 AES-128-GCM (1350 bytes) seal operations in 2020636us (14846.8 ops/sec): 20.0 MB/s [-1.5%]
Did 5502 AES-128-GCM (8192 bytes) seal operations in 2068807us (2659.5 ops/sec): 21.8 MB/s [-0.9%]
Did 2772 AES-128-GCM (16384 bytes) seal operations in 2085176us (1329.4 ops/sec): 21.8 MB/s [-0.9%]
Did 459000 AES-256-GCM (16 bytes) seal operations in 2003587us (229089.1 ops/sec): 3.7 MB/s [+117.6%]
Did 100000 AES-256-GCM (256 bytes) seal operations in 2018311us (49546.4 ops/sec): 12.7 MB/s [-8.6%]
Did 24000 AES-256-GCM (1350 bytes) seal operations in 2026975us (11840.3 ops/sec): 16.0 MB/s [-1.2%]
Did 4410 AES-256-GCM (8192 bytes) seal operations in 2079581us (2120.6 ops/sec): 17.4 MB/s [-0.6%]
Did 2226 AES-256-GCM (16384 bytes) seal operations in 2099318us (1060.3 ops/sec): 17.4 MB/s [-0.6%]

Bug: 256
Change-Id: Ib74ab7e63974d3ddae8ce5fc35c9b44e73dce305
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/37429
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin
2019-09-13 17:47:18 +00:00
committed by Adam Langley
parent 701d95a2a8
commit ccaee0a64c
3 changed files with 112 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crypto/fipsmodule/aes/asm/vpaes-armv7.pl
+59
View File
@@ -1281,6 +1281,65 @@ vpaes_decrypt_key_to_bsaes:
___
}
{
# Register-passed parameters.
my ($inp, $out, $len, $key) = map("r$_", 0..3);
# Temporaries. _vpaes_encrypt_core already uses r8..r11, so overlap $ivec and
# $tmp. $ctr is r7 because it must be preserved across calls.
my ($ctr, $ivec, $tmp) = map("r$_", 7..9);
# void vpaes_ctr32_encrypt_blocks(const uint8_t *in, uint8_t *out, size_t len,
# const AES_KEY *key, const uint8_t ivec[16]);
$code .= <<___;
.globl vpaes_ctr32_encrypt_blocks
.type vpaes_ctr32_encrypt_blocks,%function
.align 4
vpaes_ctr32_encrypt_blocks:
mov ip, sp
stmdb sp!, {r7-r11, lr}
@ This function uses q4-q7 (d8-d15), which are callee-saved.
vstmdb sp!, {d8-d15}
cmp $len, #0
@ $ivec is passed on the stack.
ldr $ivec, [ip]
beq .Lctr32_done
@ _vpaes_encrypt_core expects the key in r2, so swap $len and $key.
mov $tmp, $key
mov $key, $len
mov $len, $tmp
___
my ($len, $key) = ($key, $len);
$code .= <<___;
@ Load the IV and counter portion.
ldr $ctr, [$ivec, #12]
vld1.8 {q7}, [$ivec]
bl _vpaes_preheat
rev $ctr, $ctr @ The counter is big-endian.
.Lctr32_loop:
vmov q0, q7
vld1.8 {q6}, [$inp]! @ Load input ahead of time
bl _vpaes_encrypt_core
veor q0, q0, q6 @ XOR input and result
vst1.8 {q0}, [$out]!
subs $len, $len, #1
@ Update the counter.
add $ctr, $ctr, #1
rev $tmp, $ctr
vmov.32 q7#hi[1], $tmp
bne .Lctr32_loop
.Lctr32_done:
vldmia sp!, {d8-d15}
ldmia sp!, {r7-r11, pc} @ return
.size vpaes_ctr32_encrypt_blocks,.-vpaes_ctr32_encrypt_blocks
___
}
foreach (split("\n",$code)) {
s/\bq([0-9]+)#(lo|hi)/sprintf "d%d",2*$1+($2 eq "hi")/geo;
print $_,"\n";
crypto/fipsmodule/aes/internal.h
+1
View File
@@ -51,6 +51,7 @@ OPENSSL_INLINE int hwaes_capable(void) { return CRYPTO_is_ARMv8_AES_capable(); }
#if defined(OPENSSL_ARM)
#define BSAES
#define VPAES
#define VPAES_CTR32
OPENSSL_INLINE int bsaes_capable(void) { return CRYPTO_is_NEON_capable(); }
OPENSSL_INLINE int vpaes_capable(void) { return CRYPTO_is_NEON_capable(); }
#endif
crypto/fipsmodule/cipher/e_aes.c
+52 -19
View File
@@ -68,6 +68,48 @@
OPENSSL_MSVC_PRAGMA(warning(push))
OPENSSL_MSVC_PRAGMA(warning(disable: 4702)) // Unreachable code.
#if defined(BSAES)
static void vpaes_ctr32_encrypt_blocks_with_bsaes(const uint8_t *in,
uint8_t *out, size_t blocks,
const AES_KEY *key,
const uint8_t ivec[16]) {
// |bsaes_ctr32_encrypt_blocks| is faster than |vpaes_ctr32_encrypt_blocks|,
// but it takes at least one full 8-block batch to amortize the conversion.
if (blocks < 8) {
vpaes_ctr32_encrypt_blocks(in, out, blocks, key, ivec);
return;
}
size_t bsaes_blocks = blocks;
if (bsaes_blocks % 8 < 6) {
// |bsaes_ctr32_encrypt_blocks| internally works in 8-block batches. If the
// final batch is too small (under six blocks), it is faster to loop over
// |vpaes_encrypt|. Round |bsaes_blocks| down to a multiple of 8.
bsaes_blocks -= bsaes_blocks % 8;
}
AES_KEY bsaes;
vpaes_encrypt_key_to_bsaes(&bsaes, key);
bsaes_ctr32_encrypt_blocks(in, out, bsaes_blocks, &bsaes, ivec);
OPENSSL_cleanse(&bsaes, sizeof(bsaes));
in += 16 * bsaes_blocks;
out += 16 * bsaes_blocks;
blocks -= bsaes_blocks;
union {
uint32_t u32[4];
uint8_t u8[16];
} new_ivec;
memcpy(new_ivec.u8, ivec, 16);
uint32_t ctr = CRYPTO_bswap4(new_ivec.u32[3]) + bsaes_blocks;
new_ivec.u32[3] = CRYPTO_bswap4(ctr);
// Finish any remaining blocks with |vpaes_ctr32_encrypt_blocks|.
vpaes_ctr32_encrypt_blocks(in, out, blocks, key, new_ivec.u8);
}
#endif // BSAES
typedef struct {
union {
double align;
@@ -110,6 +152,7 @@ static int aes_init_key(EVP_CIPHER_CTX *ctx, const uint8_t *key,
dat->stream.cbc = aes_hw_cbc_encrypt;
}
} else if (bsaes_capable() && mode == EVP_CIPH_CBC_MODE) {
assert(vpaes_capable());
ret = vpaes_set_decrypt_key(key, ctx->key_len * 8, &dat->ks.ks);
if (ret == 0) {
vpaes_decrypt_key_to_bsaes(&dat->ks.ks, &dat->ks.ks);
@@ -145,11 +188,6 @@ static int aes_init_key(EVP_CIPHER_CTX *ctx, const uint8_t *key,
} else if (mode == EVP_CIPH_CTR_MODE) {
dat->stream.ctr = aes_hw_ctr32_encrypt_blocks;
}
} else if (bsaes_capable() && mode == EVP_CIPH_CTR_MODE) {
ret = aes_nohw_set_encrypt_key(key, ctx->key_len * 8, &dat->ks.ks);
// If |dat->stream.ctr| is provided, |dat->block| is never used.
dat->block = NULL;
dat->stream.ctr = bsaes_ctr32_encrypt_blocks;
} else if (vpaes_capable()) {
ret = vpaes_set_encrypt_key(key, ctx->key_len * 8, &dat->ks.ks);
dat->block = vpaes_encrypt;
@@ -159,11 +197,14 @@ static int aes_init_key(EVP_CIPHER_CTX *ctx, const uint8_t *key,
dat->stream.cbc = vpaes_cbc_encrypt;
}
#endif
#if defined(VPAES_CTR32)
if (mode == EVP_CIPH_CTR_MODE) {
#if defined(BSAES)
assert(bsaes_capable());
dat->stream.ctr = vpaes_ctr32_encrypt_blocks_with_bsaes;
#elif defined(VPAES_CTR32)
dat->stream.ctr = vpaes_ctr32_encrypt_blocks;
}
#endif
}
} else {
ret = aes_nohw_set_encrypt_key(key, ctx->key_len * 8, &dat->ks.ks);
dat->block = aes_nohw_encrypt;
@@ -252,17 +293,6 @@ ctr128_f aes_ctr_set_key(AES_KEY *aes_key, GCM128_KEY *gcm_key,
return aes_hw_ctr32_encrypt_blocks;
}
if (bsaes_capable()) {
aes_nohw_set_encrypt_key(key, key_bytes * 8, aes_key);
if (gcm_key != NULL) {
CRYPTO_gcm128_init_key(gcm_key, aes_key, aes_nohw_encrypt, 0);
}
if (out_block) {
*out_block = aes_nohw_encrypt;
}
return bsaes_ctr32_encrypt_blocks;
}
if (vpaes_capable()) {
vpaes_set_encrypt_key(key, key_bytes * 8, aes_key);
if (out_block) {
@@ -271,7 +301,10 @@ ctr128_f aes_ctr_set_key(AES_KEY *aes_key, GCM128_KEY *gcm_key,
if (gcm_key != NULL) {
CRYPTO_gcm128_init_key(gcm_key, aes_key, vpaes_encrypt, 0);
}
#if defined(VPAES_CTR32)
#if defined(BSAES)
assert(bsaes_capable());
return vpaes_ctr32_encrypt_blocks_with_bsaes;
#elif defined(VPAES_CTR32)
return vpaes_ctr32_encrypt_blocks;
#else
return NULL;