Rate limiting (#1385)

* Initial rate limiting

* Move rate limiting to client API

* Update rate limits to hopefully be self-cleaning

* Use X-Forwarded-For, add comments

* Reduce rate limit threshold

* Tweak interval

* Configurable backoff

* Review comments, set cleanup interval to 30 seconds

* Allow generate-config to produce sane CI config

* Fix Complement dockerfile

1 files changed, 31 insertions, 0 deletions

diff --git a/internal/config/config_clientapi.go b/internal/config/config_clientapi.go
index f7878276..52115491 100644
--- a/internal/config/config_clientapi.go
+++ b/internal/config/config_clientapi.go
@@ -34,6 +34,9 @@ type ClientAPI struct {
 
 	// TURN options
 	TURN TURN `yaml:"turn"`
+
+	// Rate-limiting options
+	RateLimiting RateLimiting `yaml:"rate_limiting"`
 }
 
 func (c *ClientAPI) Defaults() {
@@ -47,6 +50,7 @@ func (c *ClientAPI) Defaults() {
 	c.RecaptchaBypassSecret = ""
 	c.RecaptchaSiteVerifyAPI = ""
 	c.RegistrationDisabled = false
+	c.RateLimiting.Defaults()
 }
 
 func (c *ClientAPI) Verify(configErrs *ConfigErrors, isMonolith bool) {
@@ -61,6 +65,7 @@ func (c *ClientAPI) Verify(configErrs *ConfigErrors, isMonolith bool) {
 		checkNotEmpty(configErrs, "client_api.recaptcha_siteverify_api", string(c.RecaptchaSiteVerifyAPI))
 	}
 	c.TURN.Verify(configErrs)
+	c.RateLimiting.Verify(configErrs)
 }
 
 type TURN struct {
@@ -90,3 +95,29 @@ func (c *TURN) Verify(configErrs *ConfigErrors) {
 		}
 	}
 }
+
+type RateLimiting struct {
+	// Is rate limiting enabled or disabled?
+	Enabled bool `yaml:"enabled"`
+
+	// How many "slots" a user can occupy sending requests to a rate-limited
+	// endpoint before we apply rate-limiting
+	Threshold int64 `yaml:"threshold"`
+
+	// The cooloff period in milliseconds after a request before the "slot"
+	// is freed again
+	CooloffMS int64 `yaml:"cooloff_ms"`
+}
+
+func (r *RateLimiting) Verify(configErrs *ConfigErrors) {
+	if r.Enabled {
+		checkPositive(configErrs, "client_api.rate_limiting.threshold", r.Threshold)
+		checkPositive(configErrs, "client_api.rate_limiting.cooloff_ms", r.CooloffMS)
+	}
+}
+
+func (r *RateLimiting) Defaults() {
+	r.Enabled = true
+	r.Threshold = 5
+	r.CooloffMS = 500
+}