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synced 2025-01-23 06:32:05 +03:00
de-duplicate dn_expand, fix return value and signature, clean up
the duplicate code in dn_expand and its incorrect return values are both results of the history of the code: the version in __dns.c was originally written with no awareness of the legacy resolver API, and was later copy-and-paste duplicated to provide the legacy API. this commit is the first of a series that will restructure the internal dns code to share as much code as possible with the legacy resolver API functions. I have also removed the loop detection logic, since the output buffer length limit naturally prevents loops. in order to avoid long runtime when encountering a loop if the caller provided a ridiculously long buffer, the caller-provided length is clamped at the maximum dns name length.
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@ -134,7 +134,7 @@ int res_search(const char *, int, int, unsigned char *, int);
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int res_mkquery(int, const char *, int, int, char *, int, struct rrec *, char *, int);
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int res_send(const char *, int, char *, int);
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int dn_comp(unsigned char *, unsigned char *, int, unsigned char **, unsigned char *, unsigned char **);
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int dn_expand(unsigned char *, unsigned char *, unsigned char *, unsigned char *, int);
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int dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
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int dn_skipname(const unsigned char *, const unsigned char *);
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#ifdef __cplusplus
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@ -195,32 +195,7 @@ int __dns_query(unsigned char *r, const void *a, int family, int ptr)
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return __dns_doqueries(r, a, rr, rrcnt);
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}
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#define BITOP(a,b,op) \
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((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
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static int decname(char *s, const unsigned char *b, const unsigned char *p)
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{
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/* Remember jump destinations to detect loops and abort */
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size_t seen[PACKET_MAX/8/sizeof(size_t)] = { 0 };
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char *sz = s + HOST_NAME_MAX;
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const unsigned char *pz = b+512;
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for (;;) {
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if (p>=pz) return -1;
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else if (*p&0xc0) {
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int j = (p[0]&1) | p[1];
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if (BITOP(seen, j, &)) return -1;
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BITOP(seen, j, |=);
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p = b + j;
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} else if (*p) {
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if (p+*p+1>=pz || s+*p>=sz) return -1;
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memcpy(s, p+1, *p);
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s += *p+1;
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p += *p+1;
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s[-1] = *p ? '.' : 0;
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} else return 0;
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}
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}
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int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
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int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const unsigned char *r, int rr, int dec)
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{
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@ -249,7 +224,8 @@ int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const u
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len = p[8]*256 + p[9];
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if (p+len > r+512) return -1;
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if (p[1]==rr && len <= maxlen) {
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if (dec && decname(tmp, r, p+10)<0) return -1;
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if (dec && __dn_expand(r, r+512, p+10, tmp, sizeof tmp)<0)
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return -1;
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if (dest && limit) {
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if (dec) strcpy(dest, tmp);
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else memcpy(dest, p+10, len);
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@ -1,28 +1,27 @@
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#include <resolv.h>
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#include <string.h>
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#include "libc.h"
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#define BITOP(a,b,op) \
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((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
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int dn_expand(unsigned char *b, unsigned char *pz, unsigned char *p, unsigned char *s, int outlen)
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int __dn_expand(const unsigned char *base, const unsigned char *end, const unsigned char *src, char *dest, int space)
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{
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/* Remember jump destinations to detect loops and abort */
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size_t seen[512/8/sizeof(size_t)] = { 0 };
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unsigned char *sz = s + outlen;
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if (pz-b > 512) return -1;
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const unsigned char *p = src;
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int len = -1, j;
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if (space > 256) space = 256;
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if (p==end) return -1;
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for (;;) {
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if (p>=pz) return -1;
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else if (*p&0xc0) {
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int j = (p[0]&1) | p[1];
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if (BITOP(seen, j, &)) return -1;
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BITOP(seen, j, |=);
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p = b + j;
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if (*p & 0xc0) {
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if (p+1==end) return -1;
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j = (p[0]&1) | p[1];
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if (len < 0) len = p+2-src;
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if (j >= end-base) return -1;
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p = base+j;
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} else if (*p) {
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if (p+*p+1>=pz || s+*p>=sz) return -1;
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memcpy(s, p+1, *p);
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s += *p+1;
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p += *p+1;
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s[-1] = *p ? '.' : 0;
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} else return 0;
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j = *p+1;
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if (len < 0) len = p+1-src;
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if (j>=end-p || j>space) return -1;
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while (--j) *dest++ = *p++;
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*dest++ = *++p ? '.' : 0;
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} else return len;
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}
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}
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weak_alias(__dn_expand, dn_expand);
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