feat: add RealIP, RequestID, and RequestSize middleware

middleware/real_ip.go

@@ -0,0 +1,56 @@
+package middleware
+
+// Ported from Goji's middleware, source:
+// https://github.com/zenazn/goji/tree/master/web/middleware
+
+import (
+	"net"
+	"net/http"
+	"strings"
+)
+
+var trueClientIP = http.CanonicalHeaderKey("True-Client-IP")
+var xForwardedFor = http.CanonicalHeaderKey("X-Forwarded-For")
+var xRealIP = http.CanonicalHeaderKey("X-Real-IP")
+
+// RealIP is a middleware that sets a http.Request's RemoteAddr to the results
+// of parsing either the True-Client-IP, X-Real-IP or the X-Forwarded-For headers
+// (in that order).
+//
+// This middleware should be inserted fairly early in the middleware stack to
+// ensure that subsequent layers (e.g., request loggers) which examine the
+// RemoteAddr will see the intended value.
+//
+// You should only use this middleware if you can trust the headers passed to
+// you (in particular, the three headers this middleware uses), for example
+// because you have placed a reverse proxy like HAProxy or nginx in front of
+// chi. If your reverse proxies are configured to pass along arbitrary header
+// values from the client, or if you use this middleware without a reverse
+// proxy, malicious clients will be able to make you very sad (or, depending on
+// how you're using RemoteAddr, vulnerable to an attack of some sort).
+func RealIP(h http.Handler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		if rip := realIP(r); rip != "" {
+			r.RemoteAddr = rip
+		}
+		h.ServeHTTP(w, r)
+	}
+
+	return http.HandlerFunc(fn)
+}
+
+func realIP(r *http.Request) string {
+	var ip string
+
+	if tcip := r.Header.Get(trueClientIP); tcip != "" {
+		ip = tcip
+	} else if xrip := r.Header.Get(xRealIP); xrip != "" {
+		ip = xrip
+	} else if xff := r.Header.Get(xForwardedFor); xff != "" {
+		ip, _, _ = strings.Cut(xff, ",")
+	}
+	if ip == "" || net.ParseIP(ip) == nil {
+		return ""
+	}
+	return ip
+}

middleware/request_id.go

@@ -0,0 +1,96 @@
+package middleware
+
+// Ported from Goji's middleware, source:
+// https://github.com/zenazn/goji/tree/master/web/middleware
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"net/http"
+	"os"
+	"strings"
+	"sync/atomic"
+)
+
+// Key to use when setting the request ID.
+type ctxKeyRequestID int
+
+// RequestIDKey is the key that holds the unique request ID in a request context.
+const RequestIDKey ctxKeyRequestID = 0
+
+// RequestIDHeader is the name of the HTTP Header which contains the request id.
+// Exported so that it can be changed by developers
+var RequestIDHeader = "X-Request-Id"
+
+var prefix string
+var reqid atomic.Uint64
+
+// A quick note on the statistics here: we're trying to calculate the chance that
+// two randomly generated base62 prefixes will collide. We use the formula from
+// http://en.wikipedia.org/wiki/Birthday_problem
+//
+// P[m, n] \approx 1 - e^{-m^2/2n}
+//
+// We ballpark an upper bound for $m$ by imagining (for whatever reason) a server
+// that restarts every second over 10 years, for $m = 86400 * 365 * 10 = 315360000$
+//
+// For a $k$ character base-62 identifier, we have $n(k) = 62^k$
+//
+// Plugging this in, we find $P[m, n(10)] \approx 5.75%$, which is good enough for
+// our purposes, and is surely more than anyone would ever need in practice -- a
+// process that is rebooted a handful of times a day for a hundred years has less
+// than a millionth of a percent chance of generating two colliding IDs.
+
+func init() {
+	hostname, err := os.Hostname()
+	if hostname == "" || err != nil {
+		hostname = "localhost"
+	}
+	var buf [12]byte
+	var b64 string
+	for len(b64) < 10 {
+		rand.Read(buf[:])
+		b64 = base64.StdEncoding.EncodeToString(buf[:])
+		b64 = strings.NewReplacer("+", "", "/", "").Replace(b64)
+	}
+
+	prefix = fmt.Sprintf("%s/%s", hostname, b64[0:10])
+}
+
+// RequestID is a middleware that injects a request ID into the context of each
+// request. A request ID is a string of the form "host.example.com/random-0001",
+// where "random" is a base62 random string that uniquely identifies this go
+// process, and where the last number is an atomically incremented request
+// counter.
+func RequestID(next http.Handler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		requestID := r.Header.Get(RequestIDHeader)
+		if requestID == "" {
+			myid := reqid.Add(1)
+			requestID = fmt.Sprintf("%s-%06d", prefix, myid)
+		}
+		ctx = context.WithValue(ctx, RequestIDKey, requestID)
+		next.ServeHTTP(w, r.WithContext(ctx))
+	}
+	return http.HandlerFunc(fn)
+}
+
+// GetReqID returns a request ID from the given context if one is present.
+// Returns the empty string if a request ID cannot be found.
+func GetReqID(ctx context.Context) string {
+	if ctx == nil {
+		return ""
+	}
+	if reqID, ok := ctx.Value(RequestIDKey).(string); ok {
+		return reqID
+	}
+	return ""
+}
+
+// NextRequestID generates the next request ID in the sequence.
+func NextRequestID() uint64 {
+	return reqid.Add(1)
+}

middleware/request_size.go

@@ -0,0 +1,18 @@
+package middleware
+
+import (
+	"net/http"
+)
+
+// RequestSize is a middleware that will limit request sizes to a specified
+// number of bytes. It uses MaxBytesReader to do so.
+func RequestSize(bytes int64) func(http.Handler) http.Handler {
+	f := func(h http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+			r.Body = http.MaxBytesReader(w, r.Body, bytes)
+			h.ServeHTTP(w, r)
+		}
+		return http.HandlerFunc(fn)
+	}
+	return f
+}