Chmouel Blog

If you want to generate properly encrypted password to feed to chpasswd, the most easier and proper way is to do that from command line :

echo "encryptedpassword"|openssl passwd -1 -stdin

If you want to generate in pure python you can do it like that :

    def md5crypt(password, salt, magic='$1$'):
        import md5
        m = md5.new()
        m.update(password + magic + salt)

        # /* Then just as many characters of the MD5(pw,salt,pw) */
        mixin = md5.md5(password + salt + password).digest()
        for i in range(0, len(password)):
            m.update(mixin[i % 16])

        # /* Then something really weird... */
        # Also really broken, as far as I can tell.  -m
        i = len(password)
        while i:
            if i & 1:
                m.update('x00')
            else:
                m.update(password[0])
            i >>= 1

        final = m.digest()
        # /* and now, just to make sure things don't run too fast */
        for i in range(1000):
            m2 = md5.md5()
            if i & 1:
                m2.update(password)
            else:
                m2.update(final)
            if i % 3:
                m2.update(salt)
            if i % 7:
                m2.update(password)

            if i & 1:
                m2.update(final)
            else:
                m2.update(password)

            final = m2.digest()

        # This is the bit that uses to64() in the original code.
        itoa64 = './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
        rearranged = ''
        for a, b, c in ((0, 6, 12), (1, 7, 13), (2, 8, 14), (3, 9, 15), (4, 10, 5)):
            v = ord(final[a]) < < 16 | ord(final[b]) << 8 | ord(final[c])
            for i in range(4):
                rearranged += itoa64[v & 0x3f]; v >>= 6

        v = ord(final[11])
        for i in range(2):
            rearranged += itoa64[v & 0x3f]; v >>= 6

        return magic + salt + '$' + rearranged

You need to feed it up with a salt, like this :

    def generate_salt(count):
        import random, string
        char = string.ascii_letters + string.digits + string.punctuation.replace(':', '')
        return string.join(map(lambda x,v=char: random.choice(v), range(count)), '')

Filed under: Programming, Python, Scripts on August 17th, 2007