Bug #74961 [Com]: "Disallow non-crypto hashes in HMAC and PBKDF2" implemented poorly

Edit report at https://bugs.php.net/bug.php?id=74961&edit=1 ID: 74961 Comment by: bluebaroncanada at gmail dot com Reported by: bluebaroncanada at gmail dot com Summary: "Disallow non-crypto hashes in HMAC and PBKDF2" implemented poorly Status: Open Type: Bug Package: *Encryption and hash functions PHP Version: 7.2.0beta1 Block user comment: N Private report: N New Comment: Err. Constants. ... variable constants. Brilliant. Previous Comments: ------------------------------------------------------------------------ [2017-08-10 11:42:56] bluebaroncanada at gmail dot com Hmm, nikic. That is a pretty good reason. Then perhaps this should be extended to the user, and the docs updated to reflect that change. Unless the user has access to that function, the user will still have to perform that lookup. Perhaps there's a way to get this to constant time with a hash table or hash-name variable constants? ------------------------------------------------------------------------ [2017-08-10 09:12:04] nikic@php.net There are two reasons why this was moved into the hash structure, rather than having a secondary structure: * To make sure that there is a "single source of truth" regarding hash function metadata. This makes it impossible to forget to specify whether or not the function is cryptographic when a new hash is added. * To avoid double-lookups. It's not good to scan through lists multiple times, especially if it involves case-insensitive string comparisons. I've recently done a similar change in mbstring (https://github.com/php/php-src/commit/633a471ba0c9acc6d1cca04880c1e69e7b2dc18e), because it turned out that scanning those lists was dominating the runtime of some functions. ------------------------------------------------------------------------ [2017-08-10 03:42:49] bluebaroncanada at gmail dot com The more we add things like this, too, the heavier the code gets. The more we have to remember to implement new stuff. The more cumbersome and time consuming it is. I think, just generally, we should have high prejudice against things like that. ------------------------------------------------------------------------ [2017-08-10 03:40:16] bluebaroncanada at gmail dot com TBH, I really don't care in the end. All I'm saying is that now there's the potential for more problems. "abchash doesn't implement is_crypto = true" "xyzhash doesn't implement is_crypto = false" "Oh. My bad. I put it in the function that lists all available functions. I'll add that." "Oh. Should I check both places? Why do we have two places?" "We just invented this new class of hashing functions. Should it have is_crypto? Hmm. Well maybe yes, maybe no. It doesn't really fit that paradigm." Not to mention it's simply extraneous if there's going to be a lookup function and is_crypto. It's a make-work addition. ------------------------------------------------------------------------ [2017-08-10 03:23:55] pollita@php.net I'm confused why you care how the flag (flag mind you, not function) is implemented. Why does it matter that the algo has a bit set on its definition rather than having a completely separate lookup table? The way it looks from userspace is the same. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=74961 -- Edit this bug report at https://bugs.php.net/bug.php?id=74961&edit=1