c,python: Add the 'b' pattern for base64 encoded strings

Change the default pattern to use a short base64 string at the end.
This increses the used bits to generate a password from 65 to 73.

python/passgeny/passgeny.py

@@ -10,11 +10,14 @@ from . import bhash, phogen
 #
 # WARNING: Changing any of the parameters below will affect password generation
 #
-PASSGENY_DEFAULT_PATTERN = "^6p^6p^6ps2p100d"
+PASSGENY_DEFAULT_PATTERN = "^6p^6p^6ps3b10d"
 
 # List of special characters
 PASSGENY_SPECIAL = " +-./=_"
 
+# List of base64 characters
+PASSGENY_BASE64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+
 # Default SALT to use; this cannot be random since passgeny must
 # generate predictable passwords
 PASSGENY_SALT_DEFAULT = b"Passgeny v1"
@@ -93,6 +96,12 @@ class Passgeny:
                 x += "{:x}".format(bh.modulo(16))
             return x
 
+        def gen_base64(match):
+            blen = 1 if match[1] == "" else int(match[1])
+            b = ""
+            for l in range(blen):
+                b += PASSGENY_BASE64[bh.modulo(len(PASSGENY_BASE64))]
+            return b
 
         def gen_capitalize(match):
             nonlocal flags
@@ -104,6 +113,7 @@ class Passgeny:
                 [ '([0-9]*)s', gen_special ],
                 [ '([0-9]+)d', gen_decimal ],
                 [ '([0-9]+)x', gen_hexstr ],
+                [ '([0-9]+)b', gen_base64 ],
                 [ '\^', gen_capitalize ],
         ]