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Reworked bn_format.

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- Fix off-by-one in buffer size.
- Don't return uninitialized stack if number too large.
This commit is contained in:
Jochen Hoenicke 2018-04-04 18:27:28 +02:00 committed by Pavol Rusnak
parent 9add21439a
commit c61ab76ad7
2 changed files with 30 additions and 12 deletions
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31
bignum.c
View File

@ -990,7 +990,19 @@ size_t bn_format(const bignum256 *amnt, const char *prefix, const char *suffix,
size_t prefixlen = prefix ? strlen(prefix) : 0;
size_t suffixlen = suffix ? strlen(suffix) : 0;
char *start = &out[prefixlen + suffixlen], *end = &out[outlen];
/* add prefix to beginning of out buffer */
if (prefixlen) {
memcpy(out, prefix, prefixlen);
}
/* add suffix to end of out buffer */
if (suffixlen) {
memcpy(&out[outlen - suffixlen - 1], suffix, suffixlen);
}
/* nul terminate (even if suffix = NULL) */
out[outlen - 1] = '\0';
/* fill number between prefix and suffix (between start and end) */
char *start = &out[prefixlen], *end = &out[outlen - suffixlen - 1];
char *str = end;
#define BN_FORMAT_PUSH_CHECKED(c) \
@ -1056,19 +1068,14 @@ size_t bn_format(const bignum256 *amnt, const char *prefix, const char *suffix,
BN_FORMAT_PUSH(0);
}
size_t len = end - str;
/* finally move number to &out[prefixlen] to close the gap between
* prefix and str. len is length of number + suffix + traling 0
*/
size_t len = &out[outlen] - str;
memmove(&out[prefixlen], str, len);
if (prefixlen) {
memcpy(out, prefix, prefixlen);
}
if (suffixlen) {
memcpy(&out[prefixlen + len], suffix, suffixlen);
}
size_t length = prefixlen + len + suffixlen;
out[length] = '\0';
return length;
/* return length of number including prefix and suffix without trailing 0 */
return prefixlen + len - 1;
}
#if USE_BN_PRINT

11
test_check.c
View File

@ -622,6 +622,17 @@ START_TEST(test_bignum_format) {
r = bn_format(&a, "quite a long prefix", "even longer suffix", 60, 0, false, buf, sizeof(buf));
ck_assert_int_eq(r, 116);
ck_assert_str_eq(buf, "quite a long prefix115792089237316195.423570985008687907853269984665640564039457584007913129639935even longer suffix");
bn_read_be(fromhex("0000000000000000000000000000000000000000000000000123456789abcdef"), &a);
memset(buf, 'a', sizeof(buf));
r = bn_format(&a, "prefix", "suffix", 10, 0, false, buf, 31);
ck_assert_str_eq(buf, "prefix8198552.9216486895suffix");
ck_assert_int_eq(r, 30);
memset(buf, 'a', sizeof(buf));
r = bn_format(&a, "prefix", "suffix", 10, 0, false, buf, 30);
ck_assert_int_eq(r, 0);
ck_assert_str_eq(buf, "prefix198552.9216486895suffix");
}
END_TEST