spaces.php

aws/Aws/Signature/SignatureProvider.php

@@ -0,0 +1,126 @@
+<?php
+namespace Aws\Signature;
+
+use Aws\Exception\UnresolvedSignatureException;
+
+/**
+ * Signature providers.
+ *
+ * A signature provider is a function that accepts a version, service, and
+ * region and returns a {@see SignatureInterface} object on success or NULL if
+ * no signature can be created from the provided arguments.
+ *
+ * You can wrap your calls to a signature provider with the
+ * {@see SignatureProvider::resolve} function to ensure that a signature object
+ * is created. If a signature object is not created, then the resolve()
+ * function will throw a {@see Aws\Exception\UnresolvedSignatureException}.
+ *
+ *     use Aws\Signature\SignatureProvider;
+ *     $provider = SignatureProvider::defaultProvider();
+ *     // Returns a SignatureInterface or NULL.
+ *     $signer = $provider('v4', 's3', 'us-west-2');
+ *     // Returns a SignatureInterface or throws.
+ *     $signer = SignatureProvider::resolve($provider, 'no', 's3', 'foo');
+ *
+ * You can compose multiple providers into a single provider using
+ * {@see Aws\or_chain}. This function accepts providers as arguments and
+ * returns a new function that will invoke each provider until a non-null value
+ * is returned.
+ *
+ *     $a = SignatureProvider::defaultProvider();
+ *     $b = function ($version, $service, $region) {
+ *         if ($version === 'foo') {
+ *             return new MyFooSignature();
+ *         }
+ *     };
+ *     $c = \Aws\or_chain($a, $b);
+ *     $signer = $c('v4', 'abc', '123');     // $a handles this.
+ *     $signer = $c('foo', 'abc', '123');    // $b handles this.
+ *     $nullValue = $c('???', 'abc', '123'); // Neither can handle this.
+ */
+class SignatureProvider
+{
+    /**
+     * Resolves and signature provider and ensures a non-null return value.
+     *
+     * @param callable $provider Provider function to invoke.
+     * @param string   $version  Signature version.
+     * @param string   $service  Service name.
+     * @param string   $region   Region name.
+     *
+     * @return SignatureInterface
+     * @throws UnresolvedSignatureException
+     */
+    public static function resolve(callable $provider, $version, $service, $region)
+    {
+        $result = $provider($version, $service, $region);
+        if ($result instanceof SignatureInterface) {
+            return $result;
+        }
+
+        throw new UnresolvedSignatureException(
+            "Unable to resolve a signature for $version/$service/$region.\n"
+            . "Valid signature versions include v4 and anonymous."
+        );
+    }
+
+    /**
+     * Default SDK signature provider.
+     *
+     * @return callable
+     */
+    public static function defaultProvider()
+    {
+        return self::memoize(self::version());
+    }
+
+    /**
+     * Creates a signature provider that caches previously created signature
+     * objects. The computed cache key is the concatenation of the version,
+     * service, and region.
+     *
+     * @param callable $provider Signature provider to wrap.
+     *
+     * @return callable
+     */
+    public static function memoize(callable $provider)
+    {
+        $cache = [];
+        return function ($version, $service, $region) use (&$cache, $provider) {
+            $key = "($version)($service)($region)";
+            if (!isset($cache[$key])) {
+                $cache[$key] = $provider($version, $service, $region);
+            }
+            return $cache[$key];
+        };
+    }
+
+    /**
+     * Creates signature objects from known signature versions.
+     *
+     * This provider currently recognizes the following signature versions:
+     *
+     * - v4: Signature version 4.
+     * - anonymous: Does not sign requests.
+     *
+     * @return callable
+     */
+    public static function version()
+    {
+        return function ($version, $service, $region) {
+            switch ($version) {
+                case 's3v4':
+                case 'v4':
+                    return $service === 's3'
+                        ? new S3SignatureV4($service, $region)
+                        : new SignatureV4($service, $region);
+                case 'v4-unsigned-body':
+                    return new SignatureV4($service, $region, ['unsigned-body' => 'true']);
+                case 'anonymous':
+                    return new AnonymousSignature();
+                default:
+                    return null;
+            }
+        };
+    }
+}