add example of PAM authenticator

example/authenticator/pam/README.md

@@ -0,0 +1,31 @@
+# webfuse PAM authenticator
+
+This directory contains an example of a webfuse authenticator using PAM.
+
+The authenticator uses `username` and `password` for authentication.
+Since webfuse only provides a token, username and password are encoded as follows:
+
+    TOKEN := base64 ( USERNAME ":" PASSWORD )
+
+Example:
+
+    USERNAME := "user"
+    PASSWORD := "secret"
+    TOKEN    := base64 ( "user:secret" ) = "XNlcjpzZWNyZXQ="
+
+The utilities `webfuse_pam_token_encode` and `webfuse_pam_token_decode` can be used
+to encode and decode tokens.
+
+## Build
+
+    cmake -b build
+    cmake build
+
+## Dependencies
+
+- libpam
+- libb64
+
+## Notes
+
+- in order to make the authenticator work, read access to /etc/shadow is needed