diff options
Diffstat (limited to 'dict.c')
| -rw-r--r-- | dict.c | 79 |
1 files changed, 56 insertions, 23 deletions
@@ -19,6 +19,28 @@ #define IN_LIBXML #include "libxml.h" +#ifdef HAVE_STDLIB_H +#include <stdlib.h> +#endif +#ifdef HAVE_TIME_H +#include <time.h> +#endif + +/* + * Following http://www.ocert.org/advisories/ocert-2011-003.html + * it seems that having hash randomization might be a good idea + * when using XML with untrusted data + * Note1: that it works correctly only if compiled with WITH_BIG_KEY + * which is the default. + * Note2: the fast function used for a small dict won't protect very + * well but since the attack is based on growing a very big hash + * list we will use the BigKey algo as soon as the hash size grows + * over MIN_DICT_SIZE so this actually works + */ +#if defined(HAVE_RAND) && defined(HAVE_SRAND) && defined(HAVE_TIME) +#define DICT_RANDOMIZATION +#endif + #include <string.h> #ifdef HAVE_STDINT_H #include <stdint.h> @@ -44,23 +66,23 @@ typedef unsigned __int32 uint32_t; #define WITH_BIG_KEY #ifdef WITH_BIG_KEY -#define xmlDictComputeKey(dict, name, len) \ - (((dict)->size == MIN_DICT_SIZE) ? \ - xmlDictComputeFastKey(name, len) : \ - xmlDictComputeBigKey(name, len)) - -#define xmlDictComputeQKey(dict, prefix, plen, name, len) \ - (((prefix) == NULL) ? \ - (xmlDictComputeKey(dict, name, len)) : \ - (((dict)->size == MIN_DICT_SIZE) ? \ - xmlDictComputeFastQKey(prefix, plen, name, len) : \ - xmlDictComputeBigQKey(prefix, plen, name, len))) +#define xmlDictComputeKey(dict, name, len) \ + (((dict)->size == MIN_DICT_SIZE) ? \ + xmlDictComputeFastKey(name, len, (dict)->seed) : \ + xmlDictComputeBigKey(name, len, (dict)->seed)) + +#define xmlDictComputeQKey(dict, prefix, plen, name, len) \ + (((prefix) == NULL) ? \ + (xmlDictComputeKey(dict, name, len)) : \ + (((dict)->size == MIN_DICT_SIZE) ? \ + xmlDictComputeFastQKey(prefix, plen, name, len, (dict)->seed) : \ + xmlDictComputeBigQKey(prefix, plen, name, len, (dict)->seed))) #else /* !WITH_BIG_KEY */ -#define xmlDictComputeKey(dict, name, len) \ - xmlDictComputeFastKey(name, len) -#define xmlDictComputeQKey(dict, prefix, plen, name, len) \ - xmlDictComputeFastQKey(prefix, plen, name, len) +#define xmlDictComputeKey(dict, name, len) \ + xmlDictComputeFastKey(name, len, (dict)->seed) +#define xmlDictComputeQKey(dict, prefix, plen, name, len) \ + xmlDictComputeFastQKey(prefix, plen, name, len, (dict)->seed) #endif /* WITH_BIG_KEY */ /* @@ -98,6 +120,8 @@ struct _xmlDict { xmlDictStringsPtr strings; struct _xmlDict *subdict; + /* used for randomization */ + int seed; }; /* @@ -125,6 +149,10 @@ static int xmlInitializeDict(void) { if ((xmlDictMutex = xmlNewRMutex()) == NULL) return(0); +#ifdef DICT_RANDOMIZATION + srand(time(NULL)); +#endif + xmlDictInitialized = 1; return(1); } @@ -277,13 +305,13 @@ found_pool: */ static uint32_t -xmlDictComputeBigKey(const xmlChar* data, int namelen) { +xmlDictComputeBigKey(const xmlChar* data, int namelen, int seed) { uint32_t hash; int i; if (namelen <= 0 || data == NULL) return(0); - hash = 0; + hash = seed; for (i = 0;i < namelen; i++) { hash += data[i]; @@ -310,12 +338,12 @@ xmlDictComputeBigKey(const xmlChar* data, int namelen) { */ static unsigned long xmlDictComputeBigQKey(const xmlChar *prefix, int plen, - const xmlChar *name, int len) + const xmlChar *name, int len, int seed) { uint32_t hash; int i; - hash = 0; + hash = seed; for (i = 0;i < plen; i++) { hash += prefix[i]; @@ -346,8 +374,8 @@ xmlDictComputeBigQKey(const xmlChar *prefix, int plen, * for low hash table fill. */ static unsigned long -xmlDictComputeFastKey(const xmlChar *name, int namelen) { - unsigned long value = 0L; +xmlDictComputeFastKey(const xmlChar *name, int namelen, int seed) { + unsigned long value = seed; if (name == NULL) return(0); value = *name; @@ -381,9 +409,9 @@ xmlDictComputeFastKey(const xmlChar *name, int namelen) { */ static unsigned long xmlDictComputeFastQKey(const xmlChar *prefix, int plen, - const xmlChar *name, int len) + const xmlChar *name, int len, int seed) { - unsigned long value = 0L; + unsigned long value = (unsigned long) seed; if (plen == 0) value += 30 * (unsigned long) ':'; @@ -460,6 +488,11 @@ xmlDictCreate(void) { dict->subdict = NULL; if (dict->dict) { memset(dict->dict, 0, MIN_DICT_SIZE * sizeof(xmlDictEntry)); +#ifdef DICT_RANDOMIZATION + dict->seed = rand(); +#else + dict->seed = 0; +#endif return(dict); } xmlFree(dict); |