sudo 1.8.6p7 crashes in libc.so when using eglibc 2.17 if the account is locked (i.e. the password in /etc/shadow is "!").

This appears to be because crypt() in 2.17 onwards expects the salt input to be valid and will return NULL if it isn't.  In this case the existing password ew_epasswd is just "!" and not $id$salt$encrypted, so it errors out.

sudo assumes that there isn't ever an error when calling crypt(), so happily passes NULL to strcmp, which predictably crashes.