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Extract entropy from XML_Parser address

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Idea by Yann Droneaud, thanks!
https://bugzilla.redhat.com/show_bug.cgi?id=1197087#c21
This commit is contained in:
Sebastian Pipping 2016-03-21 19:56:05 +01:00
parent a5f2d04060
commit ca523deca4
1 changed files with 5 additions and 4 deletions

9
expat/lib/xmlparse.c
View file

@ -434,7 +434,7 @@ static ELEMENT_TYPE *
getElementType(XML_Parser parser, const ENCODING *enc,
const char *ptr, const char *end);
static unsigned long generate_hash_secret_salt(void);
static unsigned long generate_hash_secret_salt(XML_Parser parser);
static XML_Bool startParsing(XML_Parser parser);
static XML_Parser
@ -706,11 +706,12 @@ gather_time_entropy(void)
}
static unsigned long
generate_hash_secret_salt(void)
generate_hash_secret_salt(XML_Parser parser)
{
/* Process ID is 0 bits entropy if attacker has local access
* XML_Parser address is few bits of entropy if attacker has local access
* Factor is 2^61-1 (Mersenne prime M61) */
return (gather_time_entropy() ^ getpid()) * 2305843009213693951;
return (gather_time_entropy() ^ getpid() ^ (unsigned long)parser) * 2305843009213693951;
}
static XML_Bool /* only valid for root parser */
@ -718,7 +719,7 @@ startParsing(XML_Parser parser)
{
/* hash functions must be initialized before setContext() is called */
if (hash_secret_salt == 0)
hash_secret_salt = generate_hash_secret_salt();
hash_secret_salt = generate_hash_secret_salt(parser);
if (ns) {
/* implicit context only set for root parser, since child
parsers (i.e. external entity parsers) will inherit it