On Fri, Oct 18, 2019 at 7:01 AM Royce Williams <royce@techsolvency.com> wrote:

> What original caught my attention was the logic behind enforcing password quality in passwd.c during a specific era of BSD code, which exited ambiguously in a double negative of sorts, where control characters were not disallowed during password entry. (I'll try to dig up the source.)

Specifically, see the eras in which passwd.c looked something like this:

https://github.com/dank101/4.2BSD/blob/708b3890ac0c2f034f2840b5ee9125b3c83a05bc/bin/passwd.c#L69-L107

        while (c = *p++) {
                if (c >= 'a' && c <= 'z')
                        flags |= 2;
                else if (c >= 'A' && c <= 'Z')
                        flags |= 4;
                else if (c >= '0' && c <= '9')
                        flags |= 1;
                else
                        flags |= 8;
        }
        if (flags >= 7 && pwlen >= 4)
                ok = 1;

I was intrigued that the "special characters" character set was
defined negatively, such that control characters would also count.


Royce