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Fix length checks in X509_cmp_time to avoid out-of-bounds reads.

Also tighten X509_cmp_time to reject more than three fractional
seconds in the time; and to reject trailing garbage after the offset.

CVE-2015-1789

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
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ekasper authored and mattcaswell committed Apr 8, 2015
1 parent 708cf59 commit f48b83b4fb7d6689584cf25f61ca63a4891f5b11
Showing with 47 additions and 10 deletions.
  1. +47 −10 crypto/x509/x509_vfy.c
@@ -1808,47 +1808,84 @@ int X509_cmp_time(const ASN1_TIME *ctm, time_t *cmp_time)
ASN1_TIME atm;
long offset;
char buff1[24], buff2[24], *p;
int i, j;
int i, j, remaining;

p = buff1;
i = ctm->length;
remaining = ctm->length;
str = (char *)ctm->data;
/*
* Note that the following (historical) code allows much more slack in the
* time format than RFC5280. In RFC5280, the representation is fixed:
* UTCTime: YYMMDDHHMMSSZ
* GeneralizedTime: YYYYMMDDHHMMSSZ
*/
if (ctm->type == V_ASN1_UTCTIME) {
if ((i < 11) || (i > 17))
/* YYMMDDHHMM[SS]Z or YYMMDDHHMM[SS](+-)hhmm */
int min_length = sizeof("YYMMDDHHMMZ") - 1;
int max_length = sizeof("YYMMDDHHMMSS+hhmm") - 1;
if (remaining < min_length || remaining > max_length)
return 0;
memcpy(p, str, 10);
p += 10;
str += 10;
remaining -= 10;
} else {
if (i < 13)
/* YYYYMMDDHHMM[SS[.fff]]Z or YYYYMMDDHHMM[SS[.f[f[f]]]](+-)hhmm */
int min_length = sizeof("YYYYMMDDHHMMZ") - 1;
int max_length = sizeof("YYYYMMDDHHMMSS.fff+hhmm") - 1;
if (remaining < min_length || remaining > max_length)
return 0;
memcpy(p, str, 12);
p += 12;
str += 12;
remaining -= 12;
}

if ((*str == 'Z') || (*str == '-') || (*str == '+')) {
*(p++) = '0';
*(p++) = '0';
} else {
/* SS (seconds) */
if (remaining < 2)
return 0;
*(p++) = *(str++);
*(p++) = *(str++);
/* Skip any fractional seconds... */
if (*str == '.') {
remaining -= 2;
/*
* Skip any (up to three) fractional seconds...
* TODO(emilia): in RFC5280, fractional seconds are forbidden.
* Can we just kill them altogether?
*/
if (remaining && *str == '.') {
str++;
while ((*str >= '0') && (*str <= '9'))
str++;
remaining--;
for (i = 0; i < 3 && remaining; i++, str++, remaining--) {
if (*str < '0' || *str > '9')
break;
}
}

}
*(p++) = 'Z';
*(p++) = '\0';

if (*str == 'Z')
/* We now need either a terminating 'Z' or an offset. */
if (!remaining)
return 0;
if (*str == 'Z') {
if (remaining != 1)
return 0;
offset = 0;
else {
} else {
/* (+-)HHMM */
if ((*str != '+') && (*str != '-'))
return 0;
/* Historical behaviour: the (+-)hhmm offset is forbidden in RFC5280. */
if (remaining != 5)
return 0;
if (str[1] < '0' || str[1] > '9' || str[2] < '0' || str[2] > '9' ||
str[3] < '0' || str[3] > '9' || str[4] < '0' || str[4] > '9')
return 0;
offset = ((str[1] - '0') * 10 + (str[2] - '0')) * 60;
offset += (str[3] - '0') * 10 + (str[4] - '0');
if (*str == '-')

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