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password authenticaton broken?

PostPosted: Thu Jul 17, 2014 12:54 pm
by Blub
In commit 4b92354057 the code to cut off the entered password's newline character was removed. (It was probably not obvious that that's its purpose.)
This task is now performed in a somewhat unsettling way by the generate_hash function like this:
Code: Select all
   pos = (char *)memchr(entry->passwd, '\n', strlen((char *)entry->passwd));
   if (pos)
      *pos = '\0';

This is however not exactly the same (albeit equivalent when you type the password on the commandline).
The problem though arises when trying to authenticate, because the -a operation only reads the passowrd, but doesn't generate a hash. That means a password is stored without a newline in the pw file, but keeps its newline when trying to authenticate, making that impossible.

I think it would be better if generate_hash() would take a `const` input, and not mess with it, and the newline-removal needs to be added back to read_user_passwd() in gradm_pw.c

gradm_sha256.c: generate_hash()
gradm_pw.c: read_user_passwd()

Commit url: ... aa9c962775

(And maybe add a comment as it has nothing to do with what's suggested in the commit: making sure the password is null terminated. Any code of a form similar `x[strlen(x)] = 0` should raise a red flag.)