From fcc522c92335783293ac19df318415cd97fbf66b Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 14 Aug 2013 17:58:20 -0400 Subject: 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. --- src/network/__dns.c | 30 +++--------------------------- src/network/dn_expand.c | 41 ++++++++++++++++++++--------------------- 2 files changed, 23 insertions(+), 48 deletions(-) (limited to 'src') diff --git a/src/network/__dns.c b/src/network/__dns.c index 372a5871..8f3c6370 100644 --- a/src/network/__dns.c +++ b/src/network/__dns.c @@ -195,32 +195,7 @@ int __dns_query(unsigned char *r, const void *a, int family, int ptr) return __dns_doqueries(r, a, rr, rrcnt); } - -#define BITOP(a,b,op) \ - ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a)))) - -static int decname(char *s, const unsigned char *b, const unsigned char *p) -{ - /* Remember jump destinations to detect loops and abort */ - size_t seen[PACKET_MAX/8/sizeof(size_t)] = { 0 }; - char *sz = s + HOST_NAME_MAX; - const unsigned char *pz = b+512; - for (;;) { - if (p>=pz) return -1; - else if (*p&0xc0) { - int j = (p[0]&1) | p[1]; - if (BITOP(seen, j, &)) return -1; - BITOP(seen, j, |=); - p = b + j; - } else if (*p) { - if (p+*p+1>=pz || s+*p>=sz) return -1; - memcpy(s, p+1, *p); - s += *p+1; - p += *p+1; - s[-1] = *p ? '.' : 0; - } else return 0; - } -} +int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int); int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const unsigned char *r, int rr, int dec) { @@ -249,7 +224,8 @@ int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const u len = p[8]*256 + p[9]; if (p+len > r+512) return -1; if (p[1]==rr && len <= maxlen) { - if (dec && decname(tmp, r, p+10)<0) return -1; + if (dec && __dn_expand(r, r+512, p+10, tmp, sizeof tmp)<0) + return -1; if (dest && limit) { if (dec) strcpy(dest, tmp); else memcpy(dest, p+10, len); diff --git a/src/network/dn_expand.c b/src/network/dn_expand.c index 01b449bb..72a80e82 100644 --- a/src/network/dn_expand.c +++ b/src/network/dn_expand.c @@ -1,28 +1,27 @@ #include -#include +#include "libc.h" -#define BITOP(a,b,op) \ - ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a)))) - -int dn_expand(unsigned char *b, unsigned char *pz, unsigned char *p, unsigned char *s, int outlen) +int __dn_expand(const unsigned char *base, const unsigned char *end, const unsigned char *src, char *dest, int space) { - /* Remember jump destinations to detect loops and abort */ - size_t seen[512/8/sizeof(size_t)] = { 0 }; - unsigned char *sz = s + outlen; - if (pz-b > 512) return -1; + const unsigned char *p = src; + int len = -1, j; + if (space > 256) space = 256; + if (p==end) return -1; for (;;) { - if (p>=pz) return -1; - else if (*p&0xc0) { - int j = (p[0]&1) | p[1]; - if (BITOP(seen, j, &)) return -1; - BITOP(seen, j, |=); - p = b + j; + if (*p & 0xc0) { + if (p+1==end) return -1; + j = (p[0]&1) | p[1]; + if (len < 0) len = p+2-src; + if (j >= end-base) return -1; + p = base+j; } else if (*p) { - if (p+*p+1>=pz || s+*p>=sz) return -1; - memcpy(s, p+1, *p); - s += *p+1; - p += *p+1; - s[-1] = *p ? '.' : 0; - } else return 0; + j = *p+1; + if (len < 0) len = p+1-src; + if (j>=end-p || j>space) return -1; + while (--j) *dest++ = *p++; + *dest++ = *++p ? '.' : 0; + } else return len; } } + +weak_alias(__dn_expand, dn_expand); -- cgit v1.2.1