After upgrade to RH6.1, I was not able to log on: my login was not
password-protected (Not a NW machine!). The system always asked for a
password and failed, whatever was the answer.
Since "nullok" was specified in the PAM file, it should have been working.
Hints for fix: My own investigations showed me that in the
libpwdb/interface/unix/user.c, a test is made for "strlen(storedpassword)
> 1" where the comments say " != 1"... The comment is right, since the
code redirects the null password processing to a non-existent shadow
password file.
After fixing as above and recompiling libpwd, the null password feature is
OK!
I may also suggest this bug affects the "passwd" command... check