Remove triggerable Assert in hashname().

tglsfdc · tglsfdc · commit 54386f357825 · 2016-12-26T14:58:02.000-05:00
hashname() asserted that the key string it is given is shorter than NAMEDATALEN. That should surely always be true if the input is in fact a regular value of type "name". However, for reasons of coding convenience, we allow plain old C strings to be treated as "name" values in many places. Some SQL functions accept arbitrary "text" inputs, convert them to C strings, and pass them otherwise-untransformed to syscache lookups for name columns, allowing an overlength input value to trigger hashname's Assert. This would be a DOS problem, except that it only happens in assert-enabled builds which aren't recommended for production. In a production build, you'll just get a name lookup error, since regardless of the hash value computed by hashname, the later equality comparison checks can't match. Likewise, if the catalog lookup is done by seqscan or indexscan searches, there will just be a lookup error, since the name comparison functions don't contain any similar length checks, and will see an overlength input as unequal to any stored entry. After discussion we concluded that we should simply remove this Assert. It's inessential to hashname's own functionality, and having such an assertion in only some paths for name lookup is more of a foot-gun than a useful check. There may or may not be a case for the affected callers to do something other than let the name lookup fail, but we'll consider that separately; in any case we probably don't want to change such behavior in the back branches. Per report from Tushar Ahuja. Back-patch to all supported branches. Report: https://postgr.es/m/7d0809ee-6f25-c9d6-8e74-5b2967830d49@enterprisedb.com Discussion: https://postgr.es/m/17691.1482523168@sss.pgh.pa.us
diff --git a/src/backend/access/hash/hashfunc.c b/src/backend/access/hash/hashfunc.c
@@ -134,11 +134,8 @@ Datum
 hashname(PG_FUNCTION_ARGS)
 {
 	char	   *key = NameStr(*PG_GETARG_NAME(0));
-	int			keylen = strlen(key);
 
-	Assert(keylen < NAMEDATALEN);		/* else it's not truncated correctly */
-
-	return hash_any((unsigned char *) key, keylen);
+	return hash_any((unsigned char *) key, strlen(key));
 }
 
 Datum

Original file line number	Diff line number	Diff line change
`@@ -134,11 +134,8 @@ Datum`
`134`	`134`	`hashname(PG_FUNCTION_ARGS)`
`135`	`135`	`{`
`136`	`136`	`char key = NameStr(PG_GETARG_NAME(0));`
`137`		`- int keylen = strlen(key);`
`138`	`137`
`139`		`- Assert(keylen < NAMEDATALEN); /* else it's not truncated correctly */`
`140`		`-`
`141`		`- return hash_any((unsigned char *) key, keylen);`
	`138`	`+ return hash_any((unsigned char *) key, strlen(key));`
`142`	`139`	`}`
`143`	`140`
`144`	`141`	`Datum`