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Rewrite BN_rand without an extra malloc.

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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>
This commit is contained in:
David Benjamin 2018-02-04 11:09:50 -05:00 committed by Adam Langley
parent 85c2cd8a45
commit 25f3d84f4c
1 changed files with 23 additions and 33 deletions
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56
crypto/fipsmodule/bn/random.c
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@ -108,10 +108,10 @@
#include <openssl/bn.h>
#include <limits.h>
#include <string.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include <openssl/rand.h>
#include <openssl/type_check.h>
@ -121,9 +121,6 @@
int BN_rand(BIGNUM *rnd, int bits, int top, int bottom) {
uint8_t *buf = NULL;
int ret = 0, bit, bytes, mask;
if (rnd == NULL) {
return 0;
}
@ -144,48 +141,41 @@ int BN_rand(BIGNUM *rnd, int bits, int top, int bottom) {
return 1;
}
bytes = (bits + 7) / 8;
bit = (bits - 1) % 8;
mask = 0xff << (bit + 1);
buf = OPENSSL_malloc(bytes);
if (buf == NULL) {
OPENSSL_PUT_ERROR(BN, ERR_R_MALLOC_FAILURE);
goto err;
if (bits > INT_MAX - (BN_BITS2 - 1)) {
OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);
return 0;
}
// Make a random number and set the top and bottom bits.
RAND_bytes(buf, bytes);
int words = (bits + BN_BITS2 - 1) / BN_BITS2;
int bit = (bits - 1) % BN_BITS2;
const BN_ULONG kOne = 1;
const BN_ULONG kThree = 3;
BN_ULONG mask = bit < BN_BITS2 - 1 ? (kOne << (bit + 1)) - 1 : BN_MASK2;
if (!bn_wexpand(rnd, words)) {
return 0;
}
RAND_bytes((uint8_t *)rnd->d, words * sizeof(BN_ULONG));
rnd->d[words - 1] &= mask;
if (top != BN_RAND_TOP_ANY) {
if (top == BN_RAND_TOP_TWO && bits > 1) {
if (bit == 0) {
buf[0] = 1;
buf[1] |= 0x80;
rnd->d[words - 1] |= 1;
rnd->d[words - 2] |= kOne << (BN_BITS2 - 1);
} else {
buf[0] |= (3 << (bit - 1));
rnd->d[words - 1] |= kThree << (bit - 1);
}
} else {
buf[0] |= (1 << bit);
rnd->d[words - 1] |= kOne << bit;
}
}
buf[0] &= ~mask;
// Set the bottom bit if requested,
if (bottom == BN_RAND_BOTTOM_ODD) {
buf[bytes - 1] |= 1;
if (bottom == BN_RAND_BOTTOM_ODD) {
rnd->d[0] |= 1;
}
if (!BN_bin2bn(buf, bytes, rnd)) {
goto err;
}
ret = 1;
err:
OPENSSL_free(buf);
return ret;
rnd->neg = 0;
rnd->width = words;
return 1;
}
int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom) {