Add rate limit support to API

This allows us to prevent users from hammering the API every few seconds
to check if any of their packages were updated. Real world users check
as often as every 5 or 10 seconds.

Signed-off-by: Florian Pritz <bluewind@xinu.at>
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

4 files changed, 111 insertions, 0 deletions

diff --git a/conf/config.proto b/conf/config.proto
index 1750929..934d369 100644
--- a/conf/config.proto
+++ b/conf/config.proto
@@ -36,6 +36,10 @@ enable-maintenance = 1
 maintenance-exceptions = 127.0.0.1
 render-comment-cmd = /usr/local/bin/aurweb-rendercomment
 
+[ratelimit]
+request_limit = 4000
+window_length = 86400
+
 [notifications]
 notify-cmd = /usr/local/bin/aurweb-notify
 sendmail = /usr/bin/sendmail
diff --git a/schema/aur-schema.sql b/schema/aur-schema.sql
index 45272bb..79de3f2 100644
--- a/schema/aur-schema.sql
+++ b/schema/aur-schema.sql
@@ -399,3 +399,13 @@ CREATE TABLE AcceptedTerms (
 	FOREIGN KEY (UsersID) REFERENCES Users(ID) ON DELETE CASCADE,
 	FOREIGN KEY (TermsID) REFERENCES Terms(ID) ON DELETE CASCADE
 ) ENGINE = InnoDB;
+
+-- Rate limits for API
+--
+CREATE TABLE `ApiRateLimit` (
+  IP VARCHAR(45) NOT NULL,
+  Requests INT(11) NOT NULL,
+  WindowStart BIGINT(20) NOT NULL,
+  PRIMARY KEY (`ip`)
+) ENGINE = InnoDB;
+CREATE INDEX ApiRateLimitWindowStart ON ApiRateLimit (WindowStart);
diff --git a/upgrading/4.7.0.txt b/upgrading/4.7.0.txt
new file mode 100644
index 0000000..820e454
--- /dev/null
+++ b/upgrading/4.7.0.txt
@@ -0,0 +1,11 @@
+1. Add ApiRateLimit table:
+
+---
+CREATE TABLE `ApiRateLimit` (
+  IP VARCHAR(45) NOT NULL,
+  Requests INT(11) NOT NULL,
+  WindowStart BIGINT(20) NOT NULL,
+  PRIMARY KEY (`ip`)
+) ENGINE = InnoDB;
+CREATE INDEX ApiRateLimitWindowStart ON ApiRateLimit (WindowStart);
+---
diff --git a/web/lib/aurjson.class.php b/web/lib/aurjson.class.php
index 9eeaafd..b4cced0 100644
--- a/web/lib/aurjson.class.php
+++ b/web/lib/aurjson.class.php
@@ -96,6 +96,11 @@ class AurJSON {
 
 		$this->dbh = DB::connect();
 
+		if ($this->check_ratelimit($_SERVER['REMOTE_ADDR'])) {
+			header("HTTP/1.1 429 Too Many Requests");
+			return $this->json_error('Rate limit reached');
+		}
+
 		$type = str_replace('-', '_', $http_data['type']);
 		if ($type == 'info' && $this->version >= 5) {
 			$type = 'multiinfo';
@@ -131,6 +136,87 @@ class AurJSON {
 	}
 
 	/*
+	 * Check if an IP needs to be  rate limited.
+	 *
+	 * @param $ip IP of the current request
+	 *
+	 * @return true if IP needs to be rate limited, false otherwise.
+	 */
+	private function check_ratelimit($ip) {
+		$limit = config_get("ratelimit", "request_limit");
+		if ($limit == 0) {
+			return false;
+		}
+
+		$window_length = config_get("ratelimit", "window_length");
+		$this->update_ratelimit($ip);
+		$stmt = $this->dbh->prepare("
+			SELECT Requests FROM ApiRateLimit
+			WHERE IP = :ip");
+		$stmt->bindParam(":ip", $ip);
+		$result = $stmt->execute();
+
+		if (!$result) {
+			return false;
+		}
+
+		$row = $stmt->fetch(PDO::FETCH_ASSOC);
+		if ($row['Requests'] > $limit) {
+			return true;
+		}
+		return false;
+	}
+
+	/*
+	 * Update a rate limit for an IP by increasing it's requests value by one.
+	 *
+	 * @param $ip IP of the current request
+	 *
+	 * @return void
+	 */
+	private function update_ratelimit($ip) {
+		$window_length = config_get("ratelimit", "window_length");
+		$db_backend = config_get("database", "backend");
+		$time = time();
+
+		// Clean up old windows
+		$deletion_time = $time - $window_length;
+		$stmt = $this->dbh->prepare("
+			DELETE FROM ApiRateLimit
+			WHERE WindowStart < :time");
+		$stmt->bindParam(":time", $deletion_time);
+		$stmt->execute();
+
+		if ($db_backend == "mysql") {
+			$stmt = $this->dbh->prepare("
+				INSERT INTO ApiRateLimit
+				(IP, Requests, WindowStart)
+				VALUES (:ip, 1, :window_start)
+				ON DUPLICATE KEY UPDATE Requests=Requests+1");
+			$stmt->bindParam(":ip", $ip);
+			$stmt->bindParam(":window_start", $time);
+			$stmt->execute();
+		} elseif ($db_backend == "sqlite") {
+			$stmt = $this->dbh->prepare("
+				INSERT OR IGNORE INTO ApiRateLimit
+				(IP, Requests, WindowStart)
+				VALUES (:ip, 0, :window_start);");
+			$stmt->bindParam(":ip", $ip);
+			$stmt->bindParam(":window_start", $time);
+			$stmt->execute();
+
+			$stmt = $this->dbh->prepare("
+				UPDATE ApiRateLimit
+				SET Requests = Requests + 1
+				WHERE IP = :ip");
+			$stmt->bindParam(":ip", $ip);
+			$stmt->execute();
+		} else {
+			throw new RuntimeException("Unknown database backend");
+		}
+	}
+
+	/*
 	 * Returns a JSON formatted error string.
 	 *
 	 * @param $msg The error string to return