Context tools (#19)

* add context transformation logic

context/context.go

@@ -0,0 +1,84 @@
+package context
+
+import (
+	"context"
+	"net/http"
+	"strings"
+
+	"github.com/utilitywarehouse/castle-go"
+	http_internal "github.com/utilitywarehouse/castle-go/http"
+)
+
+type contextKey string
+
+func (c contextKey) String() string {
+	return "castle context key " + string(c)
+}
+
+var castleCtxKey = contextKey("castle_context")
+
+// ToCtxFromRequest adds the token and other request information (i.e. castle context) to the context.
+func ToCtxFromRequest(ctx context.Context, r *http.Request) context.Context {
+	castleCtx := castle.Context{
+		RequestToken: func() string {
+			// grab the token from header if it exists
+			if tkn := tokenFromHTTPHeader(r.Header); tkn != "" {
+				return tkn
+			}
+
+			// otherwise, try grabbing it from form
+			return tokenFromHTTPForm(r)
+		}(),
+		IP:      http_internal.IPFromRequest(r),
+		Headers: FilterHeaders(r.Header), // pass in as much context as possible
+	}
+	return context.WithValue(ctx, castleCtxKey, castleCtx)
+}
+
+func FromCtx(ctx context.Context) *castle.Context {
+	castleCtx, ok := ctx.Value(castleCtxKey).(castle.Context)
+	if ok {
+		return &castleCtx
+	}
+	return nil
+}
+
+func tokenFromHTTPHeader(header http.Header) string {
+	// recommended header name
+	if t := header.Get("X-Castle-Request-Token"); t != "" {
+		return t
+	}
+	// header name used in the frontends
+	if t := header.Get("Castle-Token"); t != "" {
+		return t
+	}
+	return ""
+}
+
+func tokenFromHTTPForm(r *http.Request) string {
+	// ParseForm is idempotent, so it's safe to call from anywhere
+	if err := r.ParseForm(); err != nil {
+		return ""
+	}
+
+	return r.Form.Get("castle_request_token")
+}
+
+func FilterHeaders(hs http.Header) map[string]string {
+	castleHeaders := make(map[string]string)
+	for key, value := range hs {
+		// Ensure cookies or authorization are never sent along.
+		// Everything else is fair game.
+		if _, ok := disallowedHeaders[strings.ToLower(key)]; ok {
+			continue
+		}
+		// View: https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html
+		castleHeaders[key] = strings.Join(value, ", ")
+	}
+	return castleHeaders
+}
+
+var disallowedHeaders = map[string]struct{}{
+	"cookie":        {},
+	"authorization": {},
+}

context/context_test.go

@@ -0,0 +1,69 @@
+package context
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/utilitywarehouse/castle-go"
+)
+
+func TestToCtxFromRequest(t *testing.T) {
+	tests := map[string]struct {
+		input    http.Request
+		expected castle.Context
+	}{
+		"castle token on header": {
+			input: func() http.Request {
+				req := httptest.NewRequest(http.MethodPost, "http://example.com", nil)
+				req.Header.Set("X-Castle-Request-Token", "foo")
+				req.RemoteAddr = "2.2.2.2"
+				return *req
+			}(),
+			expected: castle.Context{
+				IP:           "2.2.2.2",
+				Headers:      map[string]string{"X-Castle-Request-Token": "foo"},
+				RequestToken: "foo",
+			},
+		},
+		"castle token in form": {
+			input: func() http.Request {
+				req := httptest.NewRequest(http.MethodPost, "http://example.com/bar?castle_request_token=bar", nil)
+				req.RemoteAddr = "2.2.2.2"
+				return *req
+			}(),
+			expected: castle.Context{
+				IP:           "2.2.2.2",
+				Headers:      map[string]string{},
+				RequestToken: "bar",
+			},
+		},
+		"no castle token": {
+			input: func() http.Request {
+				req := http.Request{}
+				req.RemoteAddr = "2.2.2.2"
+
+				return req
+			}(),
+			expected: castle.Context{
+				IP:           "2.2.2.2",
+				Headers:      map[string]string{},
+				RequestToken: "",
+			},
+		},
+	}
+	for name, test := range tests {
+		test := test
+
+		t.Run(name, func(t *testing.T) {
+			ctx := context.Background()
+
+			gotCtx := ToCtxFromRequest(ctx, &test.input)
+			got := FromCtx(gotCtx)
+			assert.Equal(t, test.expected, *got)
+		})
+	}
+}

http/ip.go

@@ -0,0 +1,90 @@
+package http
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+)
+
+var cidrs []*net.IPNet
+
+func init() {
+	maxCidrBlocks := []string{
+		"127.0.0.1/8",    // localhost
+		"10.0.0.0/8",     // 24-bit block
+		"172.16.0.0/12",  // 20-bit block
+		"192.168.0.0/16", // 16-bit block
+		"169.254.0.0/16", // link local address
+		"::1/128",        // localhost IPv6
+		"fc00::/7",       // unique local address IPv6
+		"fe80::/10",      // link local address IPv6
+	}
+
+	cidrs = make([]*net.IPNet, len(maxCidrBlocks))
+	for i, maxCidrBlock := range maxCidrBlocks {
+		_, cidr, err := net.ParseCIDR(maxCidrBlock)
+		if err != nil {
+			panic(fmt.Sprintf("failed to parse CIDR block %q: %v", maxCidrBlock, err))
+		}
+		cidrs[i] = cidr
+	}
+}
+
+// IPFromRequest return client's real public IP address from http request headers.
+func IPFromRequest(r *http.Request) string {
+	// If we have it, return this first.
+	//
+	// https://developers.cloudflare.com/fundamentals/get-started/reference/http-request-headers/#cf-connecting-ip
+	if ip := r.Header.Get("Cf-Connecting-Ip"); ip != "" {
+		return ip
+	}
+
+	// If we have it, try to return the first global address in X-Forwarded-For
+	for _, ip := range strings.Split(r.Header.Get("X-Forwarded-For"), ",") {
+		ip = strings.TrimSpace(ip)
+		isPrivate, err := isPrivateAddress(ip)
+		if !isPrivate && err == nil {
+			return ip
+		}
+	}
+
+	// Check X-Real-Ip header next
+	if ip := r.Header.Get("X-Real-Ip"); ip != "" {
+		return ip
+	}
+
+	// If all else fails, return the remote address
+	//
+	// If there are colon in remote address, remove the port number
+	// otherwise, return remote address as is
+	var ip string
+	if strings.ContainsRune(r.RemoteAddr, ':') {
+		ip, _, _ = net.SplitHostPort(r.RemoteAddr) //nolint:errcheck
+	} else {
+		ip = r.RemoteAddr
+	}
+	return ip
+}
+
+// isPrivateAddress works by checking if the address is under private CIDR blocks.
+// List of private CIDR blocks can be seen on :
+//
+// https://en.wikipedia.org/wiki/Private_network
+//
+// https://en.wikipedia.org/wiki/Link-local_address
+func isPrivateAddress(address string) (bool, error) {
+	ipAddress := net.ParseIP(address)
+	if ipAddress == nil {
+		return false, errors.New("address is not valid")
+	}
+
+	for i := range cidrs {
+		if cidrs[i].Contains(ipAddress) {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}

http/ip_test.go

@@ -0,0 +1,75 @@
+package http_test
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	http_internal "github.com/utilitywarehouse/castle-go/http"
+)
+
+func TestIPFromRequest(t *testing.T) {
+	tests := map[string]struct {
+		input    *http.Request
+		expected string
+	}{
+		"empty": {
+			input: httpRequest(map[string]string{
+				"X-Real-Ip":        "",
+				"X-Forwarded-For":  "",
+				"Cf-Connecting-Ip": "",
+			}, ""),
+			expected: "",
+		},
+		"cf-connecting-ip": {
+			input: httpRequest(map[string]string{
+				"X-Real-Ip":        "foo",
+				"X-Forwarded-For":  "bar",
+				"Cf-Connecting-Ip": "cf-connecting-ip",
+			}, "foobar"),
+			expected: "cf-connecting-ip",
+		},
+		"x-forwarded-for": {
+			input: httpRequest(map[string]string{
+				"X-Real-Ip":        "foo",
+				"X-Forwarded-For":  "127.0.0.1, 109.14.23.2",
+				"Cf-Connecting-Ip": "",
+			}, "foobar"),
+			expected: "109.14.23.2",
+		},
+		"x-real-ip": {
+			input: httpRequest(map[string]string{
+				"X-Real-Ip":        "x-real-ip",
+				"X-Forwarded-For":  "",
+				"Cf-Connecting-Ip": "",
+			}, "foobar"),
+			expected: "x-real-ip",
+		},
+		"remote-addr": {
+			input: httpRequest(map[string]string{
+				"X-Real-Ip":        "",
+				"X-Forwarded-For":  "",
+				"Cf-Connecting-Ip": "",
+			}, "remote-addr:8080"),
+			expected: "remote-addr",
+		},
+	}
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			got := http_internal.IPFromRequest(test.input)
+			assert.Equal(t, test.expected, got)
+		})
+	}
+}
+
+func httpRequest(headers map[string]string, remoteAddr string) *http.Request {
+	r := &http.Request{
+		RemoteAddr: remoteAddr,
+		Header:     make(http.Header),
+	}
+	for k, v := range headers {
+		r.Header.Set(k, v)
+	}
+	return r
+}