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fix dn_expand empty name handling and offsets to 0

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Empty name was rejected in dn_expand since commit
56b57f37a4
which is a regression as reported by Natanael Copa.

Furthermore if an offset pointer in a compressed name
pointed to a terminating 0 byte (instead of a label)
the returned name was not null terminated.

(cherry picked from commit 49d2c8c6bc)
This commit is contained in:
Szabolcs Nagy 2014-09-04 18:29:16 +02:00 committed by Rich Felker
parent 53f270f964
commit 83eb88d6c2
1 changed files with 9 additions and 6 deletions
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15
src/network/dn_expand.c
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@ -4,11 +4,13 @@
int __dn_expand(const unsigned char *base, const unsigned char *end, const unsigned char *src, char *dest, int space)
{
const unsigned char *p = src;
char *dend = dest + (space > 254 ? 254 : space);
char *dend, *dbegin = dest;
int len = -1, i, j;
if (p==end || !*p) return -1;
if (p==end || space <= 0) return -1;
dend = dest + (space > 254 ? 254 : space);
/* detect reference loop using an iteration counter */
for (i=0; i < end-base; i+=2) {
/* loop invariants: p<end, dest<dend */
if (*p & 0xc0) {
if (p+1==end) return -1;
j = ((p[0] & 0x3f) << 8) | p[1];
@ -16,11 +18,12 @@ int __dn_expand(const unsigned char *base, const unsigned char *end, const unsig
if (j >= end-base) return -1;
p = base+j;
} else if (*p) {
j = *p+1;
if (j>=end-p || j>dend-dest) return -1;
while (--j) *dest++ = *++p;
*dest++ = *++p ? '.' : 0;
if (dest != dbegin) *dest++ = '.';
j = *p++;
if (j >= end-p || j >= dend-dest) return -1;
while (j--) *dest++ = *p++;
} else {
*dest = 0;
if (len < 0) len = p+1-src;
return len;
}