1 files changed, 104 insertions, 0 deletions

diff --git a/doc/md/REST-API.md b/doc/md/REST-API.md
new file mode 100644
index 00000000..8f3f7303
--- /dev/null
+++ b/doc/md/REST-API.md
@@ -0,0 +1,104 @@
+## Usage
+
+See the [REST API documentation](http://shaarli.github.io/api-documentation/).
+
+## Authentication
+
+All requests to Shaarli's API must include a JWT token to verify their authenticity.
+
+This token has to be included as an HTTP header called `Authentication: Bearer <jwt token>`.
+
+JWT resources :
+
+ * [jwt.io](https://jwt.io) (including a list of client per language).
+ * RFC : https://tools.ietf.org/html/rfc7519
+ * https://float-middle.com/json-web-tokens-jwt-vs-sessions/
+ * HackerNews thread: https://news.ycombinator.com/item?id=11929267
+
+
+### Shaarli JWT Token
+
+JWT tokens are composed by three parts, separated by a dot `.` and encoded in base64:
+
+```
+[header].[payload].[signature]
+```
+
+#### Header
+
+Shaarli only allow one hash algorithm, so the header will always be the same:
+
+```json
+{
+    "typ": "JWT",
+    "alg": "HS512"
+}
+```
+
+Encoded in base64, it gives:
+
+```
+ewogICAgICAgICJ0eXAiOiAiSldUIiwKICAgICAgICAiYWxnIjogIkhTNTEyIgogICAgfQ==
+```
+
+#### Payload
+
+**Validity duration**
+
+To avoid infinite token validity, JWT tokens must include their creation date in UNIX timestamp format (timezone independant - UTC) under the key `iat` (issued at). This token will be accepted during 9 minutes.
+
+```json
+{
+    "iat": 1468663519
+}
+```
+
+See [RFC reference](https://tools.ietf.org/html/rfc7519#section-4.1.6).
+
+
+#### Signature
+
+The signature authenticate the token validity. It contains the base64 of the header and the body, separated by a dot `.`, hashed in SHA512 with the API secret available in Shaarli administration page.
+
+Signature example with PHP:
+
+```php
+$content = base64_encode($header) . '.' . base64_encode($payload);
+$signature = hash_hmac('sha512', $content, $secret);
+```
+
+
+### Complete example
+
+#### PHP
+
+```php
+function generateToken($secret) {
+    $header = base64_encode('{
+        "typ": "JWT",
+        "alg": "HS512"
+    }');
+    $payload = base64_encode('{
+        "iat": '. time() .'
+    }');
+    $signature = hash_hmac('sha512', $header .'.'. $payload , $secret);
+    return $header .'.'. $payload .'.'. $signature;
+}
+
+$secret = 'mysecret';
+$token = generateToken($secret);
+echo $token;
+```
+
+> `ewogICAgICAgICJ0eXAiOiAiSldUIiwKICAgICAgICAiYWxnIjogIkhTNTEyIgogICAgfQ==.ewogICAgICAgICJpYXQiOiAxNDY4NjY3MDQ3CiAgICB9.1d2c54fa947daf594fdbf7591796195652c8bc63bffad7f6a6db2a41c313f495a542cbfb595acade79e83f3810d709b4251d7b940bbc10b531a6e6134af63a68`
+
+```php
+$options = [
+    'http' => [
+        'method' => 'GET',
+        'jwt' => $token,
+    ],
+];
+$context = stream_context_create($options);
+file_get_contents($apiEndpoint, false, $context);
+```