WIP: doc

Author: Snawoot

README.md

@@ -1,2 +1,40 @@
-# basic_hmac_auth
-HMAC auth helper for Squid
+# basic\_hmac\_auth
+
+HMAC auth helper for Squid.
+
+TODO: Tell about format and idea.
+
+## Usage
+
+This auth helper can be used with configuration like this:
+
+```
+auth_param basic program /usr/local/bin/basic_hmac_auth -secret 1be3ada09688ca3c4a674a7d2e285a5a04ee423e082ae6c6b91946e2853af239
+auth_param basic children 8 startup=8 idle=8 concurrency=50
+auth_param basic credentialsttl 15 minutes
+auth_param basic casesensitive on
+acl authenticated proxy_auth REQUIRED
+http_access allow authenticated
+http_access deny all
+```
+
+> [!IMPORTANT]  
+> Note that this helper works **only** with concurrent helper protocol, so `concurrency=` parameter **must** be greater than zero.
+
+> [!TIP]
+> HMAC shared secret can be also specified in file referenced by `-secret-file` command line option or with `BASIC_AUTH_HMAC_SECRET` environment variable.
+
+## Synopsis
+
+```
+$ basic_hmac_auth -h
+Usage of /usr/local/bin/basic_hmac_auth:
+  -buffer-size int
+    	initial buffer size for stream parsing
+  -secret string
+    	hex-encoded HMAC secret value
+  -secret-file string
+    	file containing single line with hex-encoded secret
+  -version
+    	show program version and exit
+```