diff --git a/apps/files_external/lib/Lib/Backend/AmazonS3.php b/apps/files_external/lib/Lib/Backend/AmazonS3.php
index c975901512..5625805601 100644
--- a/apps/files_external/lib/Lib/Backend/AmazonS3.php
+++ b/apps/files_external/lib/Lib/Backend/AmazonS3.php
@@ -53,6 +53,8 @@ class AmazonS3 extends Backend {
 					->setType(DefinitionParameter::VALUE_BOOLEAN),
 				(new DefinitionParameter('use_path_style', $l->t('Enable Path Style')))
 					->setType(DefinitionParameter::VALUE_BOOLEAN),
+				(new DefinitionParameter('legacy_auth', $l->t('Legacy (v2) authentication')))
+					->setType(DefinitionParameter::VALUE_BOOLEAN),
 			])
 			->addAuthScheme(AccessKey::SCHEME_AMAZONS3_ACCESSKEY)
 			->setLegacyAuthMechanism($legacyAuth)
diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 61df49cd51..93e792a7f4 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -594,6 +594,7 @@ return array(
     'OC\\Files\\ObjectStore\\S3' => $baseDir . '/lib/private/Files/ObjectStore/S3.php',
     'OC\\Files\\ObjectStore\\S3ConnectionTrait' => $baseDir . '/lib/private/Files/ObjectStore/S3ConnectionTrait.php',
     'OC\\Files\\ObjectStore\\S3ObjectTrait' => $baseDir . '/lib/private/Files/ObjectStore/S3ObjectTrait.php',
+    'OC\\Files\\ObjectStore\\S3Signature' => $baseDir . '/lib/private/Files/ObjectStore/S3Signature.php',
     'OC\\Files\\ObjectStore\\StorageObjectStore' => $baseDir . '/lib/private/Files/ObjectStore/StorageObjectStore.php',
     'OC\\Files\\ObjectStore\\Swift' => $baseDir . '/lib/private/Files/ObjectStore/Swift.php',
     'OC\\Files\\Search\\SearchBinaryOperator' => $baseDir . '/lib/private/Files/Search/SearchBinaryOperator.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index aa5990466f..88bb9c65ff 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -624,6 +624,7 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OC\\Files\\ObjectStore\\S3' => __DIR__ . '/../../..' . '/lib/private/Files/ObjectStore/S3.php',
         'OC\\Files\\ObjectStore\\S3ConnectionTrait' => __DIR__ . '/../../..' . '/lib/private/Files/ObjectStore/S3ConnectionTrait.php',
         'OC\\Files\\ObjectStore\\S3ObjectTrait' => __DIR__ . '/../../..' . '/lib/private/Files/ObjectStore/S3ObjectTrait.php',
+        'OC\\Files\\ObjectStore\\S3Signature' => __DIR__ . '/../../..' . '/lib/private/Files/ObjectStore/S3Signature.php',
         'OC\\Files\\ObjectStore\\StorageObjectStore' => __DIR__ . '/../../..' . '/lib/private/Files/ObjectStore/StorageObjectStore.php',
         'OC\\Files\\ObjectStore\\Swift' => __DIR__ . '/../../..' . '/lib/private/Files/ObjectStore/Swift.php',
         'OC\\Files\\Search\\SearchBinaryOperator' => __DIR__ . '/../../..' . '/lib/private/Files/Search/SearchBinaryOperator.php',
diff --git a/lib/private/Files/ObjectStore/S3ConnectionTrait.php b/lib/private/Files/ObjectStore/S3ConnectionTrait.php
index fdda19ff70..e6ae0f6cb5 100644
--- a/lib/private/Files/ObjectStore/S3ConnectionTrait.php
+++ b/lib/private/Files/ObjectStore/S3ConnectionTrait.php
@@ -21,6 +21,7 @@
 
 namespace OC\Files\ObjectStore;
 
+use Aws\ClientResolver;
 use Aws\S3\Exception\S3Exception;
 use Aws\S3\S3Client;
 
@@ -83,11 +84,15 @@ trait S3ConnectionTrait {
 			],
 			'endpoint' => $base_url,
 			'region' => $this->params['region'],
-			'use_path_style_endpoint' => isset($this->params['use_path_style']) ? $this->params['use_path_style'] : false
+			'use_path_style_endpoint' => isset($this->params['use_path_style']) ? $this->params['use_path_style'] : false,
+			'signature_provider' => \Aws\or_chain([self::class, 'legacySignatureProvider'], ClientResolver::_default_signature_provider())
 		];
 		if (isset($this->params['proxy'])) {
 			$options['request.options'] = ['proxy' => $this->params['proxy']];
 		}
+		if (isset($this->params['legacy_auth']) && $this->params['legacy_auth']) {
+			$options['signature_version'] = 'v2';
+		}
 		$this->connection = new S3Client($options);
 
 		if (!S3Client::isBucketDnsCompatible($this->bucket)) {
@@ -117,4 +122,14 @@ trait S3ConnectionTrait {
 			sleep($this->timeout);
 		}
 	}
+
+	public static function legacySignatureProvider($version, $service, $region) {
+		switch ($version) {
+			case 'v2':
+			case 's3':
+				return new S3Signature();
+			default:
+				return null;
+		}
+	}
 }
diff --git a/lib/private/Files/ObjectStore/S3Signature.php b/lib/private/Files/ObjectStore/S3Signature.php
new file mode 100644
index 0000000000..d5bfbf4e53
--- /dev/null
+++ b/lib/private/Files/ObjectStore/S3Signature.php
@@ -0,0 +1,204 @@
+<?php
+
+namespace OC\Files\ObjectStore;
+
+use Aws\Credentials\CredentialsInterface;
+use Aws\S3\S3Client;
+use Aws\S3\S3UriParser;
+use Aws\Signature\SignatureInterface;
+use GuzzleHttp\Psr7;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Legacy Amazon S3 signature implementation
+ */
+class S3Signature implements SignatureInterface
+{
+	/** @var array Query string values that must be signed */
+	private $signableQueryString = [
+		'acl', 'cors', 'delete', 'lifecycle', 'location', 'logging',
+		'notification', 'partNumber', 'policy', 'requestPayment',
+		'response-cache-control', 'response-content-disposition',
+		'response-content-encoding', 'response-content-language',
+		'response-content-type', 'response-expires', 'restore', 'tagging',
+		'torrent', 'uploadId', 'uploads', 'versionId', 'versioning',
+		'versions', 'website'
+	];
+
+	/** @var array Sorted headers that must be signed */
+	private $signableHeaders = ['Content-MD5', 'Content-Type'];
+
+	/** @var \Aws\S3\S3UriParser S3 URI parser */
+	private $parser;
+
+	public function __construct()
+	{
+		$this->parser = new S3UriParser();
+		// Ensure that the signable query string parameters are sorted
+		sort($this->signableQueryString);
+	}
+
+	public function signRequest(
+		RequestInterface $request,
+		CredentialsInterface $credentials
+	) {
+		$request = $this->prepareRequest($request, $credentials);
+		$stringToSign = $this->createCanonicalizedString($request);
+		$auth = 'AWS '
+			. $credentials->getAccessKeyId() . ':'
+			. $this->signString($stringToSign, $credentials);
+
+		return $request->withHeader('Authorization', $auth);
+	}
+
+	public function presign(
+		RequestInterface $request,
+		CredentialsInterface $credentials,
+		$expires
+	) {
+		$query = [];
+		// URL encoding already occurs in the URI template expansion. Undo that
+		// and encode using the same encoding as GET object, PUT object, etc.
+		$uri = $request->getUri();
+		$path = S3Client::encodeKey(rawurldecode($uri->getPath()));
+		$request = $request->withUri($uri->withPath($path));
+
+		// Make sure to handle temporary credentials
+		if ($token = $credentials->getSecurityToken()) {
+			$request = $request->withHeader('X-Amz-Security-Token', $token);
+			$query['X-Amz-Security-Token'] = $token;
+		}
+
+		if ($expires instanceof \DateTime) {
+			$expires = $expires->getTimestamp();
+		} elseif (!is_numeric($expires)) {
+			$expires = strtotime($expires);
+		}
+
+		// Set query params required for pre-signed URLs
+		$query['AWSAccessKeyId'] = $credentials->getAccessKeyId();
+		$query['Expires'] = $expires;
+		$query['Signature'] = $this->signString(
+			$this->createCanonicalizedString($request, $expires),
+			$credentials
+		);
+
+		// Move X-Amz-* headers to the query string
+		foreach ($request->getHeaders() as $name => $header) {
+			$name = strtolower($name);
+			if (strpos($name, 'x-amz-') === 0) {
+				$query[$name] = implode(',', $header);
+			}
+		}
+
+		$queryString = http_build_query($query, null, '&', PHP_QUERY_RFC3986);
+
+		return $request->withUri($request->getUri()->withQuery($queryString));
+	}
+
+	/**
+	 * @param RequestInterface     $request
+	 * @param CredentialsInterface $creds
+	 *
+	 * @return RequestInterface
+	 */
+	private function prepareRequest(
+		RequestInterface $request,
+		CredentialsInterface $creds
+	) {
+		$modify = [
+			'remove_headers' => ['X-Amz-Date'],
+			'set_headers'    => ['Date' => gmdate(\DateTime::RFC2822)]
+		];
+
+		// Add the security token header if one is being used by the credentials
+		if ($token = $creds->getSecurityToken()) {
+			$modify['set_headers']['X-Amz-Security-Token'] = $token;
+		}
+
+		return Psr7\modify_request($request, $modify);
+	}
+
+	private function signString($string, CredentialsInterface $credentials)
+	{
+		return base64_encode(
+			hash_hmac('sha1', $string, $credentials->getSecretKey(), true)
+		);
+	}
+
+	private function createCanonicalizedString(
+		RequestInterface $request,
+		$expires = null
+	) {
+		$buffer = $request->getMethod() . "\n";
+
+		// Add the interesting headers
+		foreach ($this->signableHeaders as $header) {
+			$buffer .= $request->getHeaderLine($header) . "\n";
+		}
+
+		$date = $expires ?: $request->getHeaderLine('date');
+		$buffer .= "{$date}\n"
+			. $this->createCanonicalizedAmzHeaders($request)
+			. $this->createCanonicalizedResource($request);
+
+		return $buffer;
+	}
+
+	private function createCanonicalizedAmzHeaders(RequestInterface $request)
+	{
+		$headers = [];
+		foreach ($request->getHeaders() as $name => $header) {
+			$name = strtolower($name);
+			if (strpos($name, 'x-amz-') === 0) {
+				$value = implode(',', $header);
+				if (strlen($value) > 0) {
+					$headers[$name] = $name . ':' . $value;
+				}
+			}
+		}
+
+		if (!$headers) {
+			return '';
+		}
+
+		ksort($headers);
+
+		return implode("\n", $headers) . "\n";
+	}
+
+	private function createCanonicalizedResource(RequestInterface $request)
+	{
+		$data = $this->parser->parse($request->getUri());
+		$buffer = '/';
+
+		if ($data['bucket']) {
+			$buffer .= $data['bucket'];
+			if (!empty($data['key']) || !$data['path_style']) {
+				$buffer .= '/' . $data['key'];
+			}
+		}
+
+		// Add sub resource parameters if present.
+		$query = $request->getUri()->getQuery();
+
+		if ($query) {
+			$params = Psr7\parse_query($query);
+			$first = true;
+			foreach ($this->signableQueryString as $key) {
+				if (array_key_exists($key, $params)) {
+					$value = $params[$key];
+					$buffer .= $first ? '?' : '&';
+					$first = false;
+					$buffer .= $key;
+					// Don't add values for empty sub-resources
+					if (strlen($value)) {
+						$buffer .= "={$value}";
+					}
+				}
+			}
+		}
+
+		return $buffer;
+	}
+}