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Tidy up BN decimal and hex decode functions.

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Move the bn_expand call inside decode_hex; it's an implementation detail of
hex-decoding. decode_dec instead works with BN_mul_word and BN_add_word so it
can just rely on BN internally expanding things and check the return value.

Also clean up the decode_hex loop so it's somewhat more readable and check for
INT_MAX in bn_x2bn. It uses int over size_t rather pervasively, but while I'm
here at least make that function check overflow.

BUG=517474

Change-Id: I4f043973ee43071a02ea5d4313a8fdaf12404e84
Reviewed-on: https://boringssl-review.googlesource.com/5679
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2015-08-11 11:47:56 -04:00 committed by Adam Langley
parent 2b9ec70558
commit 0257cffb4e
1 changed files with 55 additions and 41 deletions
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96
crypto/bn/convert.c
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@ -56,7 +56,9 @@
#include <openssl/bn.h>
#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
@ -227,47 +229,59 @@ char *BN_bn2hex(const BIGNUM *bn) {
return buf;
}
/* decode_hex decodes |i| bytes of hex data from |in| and updates |bn|. */
static void decode_hex(BIGNUM *bn, const char *in, int i) {
int h, m, j, k, c;
BN_ULONG l=0;
j = i; /* least significant 'hex' */
h = 0;
while (j > 0) {
m = ((BN_BYTES * 2) <= j) ? (BN_BYTES * 2) : j;
l = 0;
for (;;) {
c = in[j - m];
if ((c >= '0') && (c <= '9')) {
k = c - '0';
} else if ((c >= 'a') && (c <= 'f')) {
k = c - 'a' + 10;
} else if ((c >= 'A') && (c <= 'F')) {
k = c - 'A' + 10;
} else {
k = 0; /* paranoia */
}
l = (l << 4) | k;
if (--m <= 0) {
bn->d[h++] = l;
break;
}
}
j -= (BN_BYTES * 2);
/* decode_hex decodes |in_len| bytes of hex data from |in| and updates |bn|. */
static int decode_hex(BIGNUM *bn, const char *in, int in_len) {
if (in_len > INT_MAX/4) {
OPENSSL_PUT_ERROR(BN, BN_R_BIGNUM_TOO_LONG);
return 0;
}
/* |in_len| is the number of hex digits. */
if (bn_expand(bn, in_len * 4) == NULL) {
return 0;
}
bn->top = h;
int i = 0;
while (in_len > 0) {
/* Decode one |BN_ULONG| at a time. */
int todo = BN_BYTES * 2;
if (todo > in_len) {
todo = in_len;
}
BN_ULONG word = 0;
int j;
for (j = todo; j > 0; j--) {
char c = in[in_len - j];
BN_ULONG hex;
if (c >= '0' && c <= '9') {
hex = c - '0';
} else if (c >= 'a' && c <= 'f') {
hex = c - 'a' + 10;
} else if (c >= 'A' && c <= 'F') {
hex = c - 'A' + 10;
} else {
hex = 0;
/* This shouldn't happen. The caller checks |isxdigit|. */
assert(0);
}
word = (word << 4) | hex;
}
bn->d[i++] = word;
in_len -= todo;
}
assert(i <= bn->dmax);
bn->top = i;
return 1;
}
/* decode_dec decodes |in_len| bytes of decimal data from |in| and updates |bn|. */
static void decode_dec(BIGNUM *bn, const char *in, int in_len) {
static int decode_dec(BIGNUM *bn, const char *in, int in_len) {
int i, j;
BN_ULONG l = 0;
/* Decode |BN_DEC_NUM| digits at a time. */
j = BN_DEC_NUM - (in_len % BN_DEC_NUM);
if (j == BN_DEC_NUM) {
j = 0;
@ -277,15 +291,18 @@ static void decode_dec(BIGNUM *bn, const char *in, int in_len) {
l *= 10;
l += in[i] - '0';
if (++j == BN_DEC_NUM) {
BN_mul_word(bn, BN_DEC_CONV);
BN_add_word(bn, l);
if (!BN_mul_word(bn, BN_DEC_CONV) ||
!BN_add_word(bn, l)) {
return 0;
}
l = 0;
j = 0;
}
}
return 1;
}
typedef void (*decode_func) (BIGNUM *bn, const char *in, int i);
typedef int (*decode_func) (BIGNUM *bn, const char *in, int in_len);
typedef int (*char_test_func) (int c);
static int bn_x2bn(BIGNUM **outp, const char *in, decode_func decode, char_test_func want_char) {
@ -302,7 +319,7 @@ static int bn_x2bn(BIGNUM **outp, const char *in, decode_func decode, char_test_
in++;
}
for (i = 0; want_char((unsigned char)in[i]); i++) {}
for (i = 0; want_char((unsigned char)in[i]) && i + neg < INT_MAX; i++) {}
num = i + neg;
if (outp == NULL) {
@ -320,13 +337,10 @@ static int bn_x2bn(BIGNUM **outp, const char *in, decode_func decode, char_test_
BN_zero(ret);
}
/* i is the number of hex digests; */
if (bn_expand(ret, i * 4) == NULL) {
if (!decode(ret, in, i)) {
goto err;
}
decode(ret, in, i);
bn_correct_top(ret);
if (!BN_is_zero(ret)) {
ret->neg = neg;