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r9692@catbus: nickm | 2007-01-21 12:04:22 -0500

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Detect pointer loops in DNS requests and replies; avoid infinite loop on such malformed replies.  Fixes bug 380.


svn:r9378
This commit is contained in:
Nick Mathewson 2007-01-21 17:05:10 +00:00
parent bcbd289af5
commit ff62a4d91b
2 changed files with 7 additions and 0 deletions
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2
ChangeLog
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@ -27,6 +27,8 @@ Changes in version 0.1.2.7-alpha - 2007-??-??
- If our system clock jumps back in time, don't publish a negative
uptime in the descriptor. Also, don't let the global rate limiting
buckets go absurdly negative.
- Detect and reject malformed DNS responses containing circular
pointer loops.
o Minor bugfixes:
- When computing clock skew from directory HTTP headers, consider what

5
src/or/eventdns.c
View File

@ -736,6 +736,7 @@ static inline int
name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) {
int name_end = -1;
int j = *idx;
int ptr_count = 0;
#define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while(0);
#define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while(0);
#define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while(0);
@ -759,7 +760,11 @@ name_parse(u8 *packet, int length, int *idx, char *name_out, int name_out_len) {
GET8(ptr_low);
if (name_end < 0) name_end = j;
j = (((int)label_len & 0x3f) << 8) + ptr_low;
/* Make sure that the target offset is in-bounds. */
if (j < 0 || j >= length) return -1;
/* If we've jumped more times than there are characters in the
* message, we must have a loop. */
if (++ptr_count > length) return -1;
continue;
}
if (label_len > 63) return -1;