Optimize handling of prepended salts of at least the fast hash's block size #saltfail
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- Dominant language
- C
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Description
Nice post by Atom
http://hashcat.net/forum/thread-4429.html
The context is ColdFusion's sha256(salt.sha1(pass)) but the hash functions are not important, it applies to things like MD5(salt.pass) as well. The flaw is it's a salt with a length that "equals or is greater than the blocksize of the hash" and that it's prepended to the password, as opposed to appended. This means, in JtR context, we can run the first digest operation in get_salt() and get it completely out of the hot loops.
We have formats that already use this optimization but we probably have some that don't. We should find them, list them here and fix them.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing the format implementations that use get_salt() and comparing them with formats that already apply this optimization. Identify formats handling prepended salts at least the fast hash block size, then confirm all applicable formats move the first digest operation out of the hot loops. No specific files or tests are named in the issue.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c
- Domain
- cryptography, security
- Issue type
- Refactor
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100