config: add prefix, path and regex options

proxy: support prefix, path and regex options

config/policy.go

@@ -24,6 +24,11 @@ type Policy struct {
 	Source      *HostnameURL `yaml:",omitempty" json:"source,omitempty"`
 	Destination *url.URL     `yaml:",omitempty" json:"destination,omitempty"`
 
+	// Additional route matching options
+	Prefix string `mapstructure:"prefix" yaml:"prefix,omitempty" json:"prefix,omitempty"`
+	Path string `mapstructure:"path" yaml:"path,omitempty" json:"path,omitempty"`
+	Regex string `mapstructure:"regex" yaml:"regex,omitempty" json:"regex,omitempty"`
+
 	// Allow unauthenticated HTTP OPTIONS requests as per the CORS spec
 	// https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#Preflighted_requests
 	CORSAllowPreflight bool `mapstructure:"cors_allow_preflight" yaml:"cors_allow_preflight,omitempty"`

proxy/proxy.go

@@ -14,6 +14,8 @@ import (
 	"net/http"
 	stdhttputil "net/http/httputil"
 	"net/url"
+	"regexp"
+	"strings"
 	"time"
 
 	"github.com/gorilla/mux"
@@ -230,8 +232,8 @@ func (p *Proxy) reverseProxyHandler(r *mux.Router, policy config.Policy) *mux.Ro
 
 	// 4. Override any custom transport settings (e.g. TLS settings, etc)
 	proxy.Transport = p.roundTripperFromPolicy(&policy)
-	// 5. Create a sub-router for a given route's hostname (`httpbin.corp.example.com`)
-	rp := r.Host(policy.Source.Host).Subrouter()
+	// 5. Create a sub-router with a matcher derived from the policy (host, path, etc...)
+	rp := r.MatcherFunc(routeMatcherFuncFromPolicy(policy)).Subrouter()
 	rp.PathPrefix("/").Handler(proxy)
 
 	// Optional: If websockets are enabled, do not set a handler request timeout
@@ -323,3 +325,44 @@ func (p *Proxy) roundTripperFromPolicy(policy *config.Policy) http.RoundTripper
 func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	p.Handler.ServeHTTP(w, r)
 }
+
+
+// routeMatcherFuncFromPolicy returns a mux matcher function which compares an http request with a policy.
+//
+// Routes can be filtered by the `source`, `prefix`, `path` and `regex` fields in the policy config.
+func routeMatcherFuncFromPolicy(policy config.Policy) mux.MatcherFunc {
+	// match by source
+	sourceMatches := func(r *http.Request) bool {
+		return r.Host == policy.Source.Host &&
+			strings.HasPrefix(r.URL.Path, policy.Source.Path)
+	}
+
+	// match by prefix
+	prefixMatches := func(r *http.Request) bool {
+		return policy.Prefix == "" ||
+			strings.HasPrefix(r.URL.Path, policy.Prefix)
+	}
+
+	// match by path
+	pathMatches := func(r *http.Request) bool {
+		return policy.Path == "" ||
+			r.URL.Path == policy.Path
+	}
+
+	// match by path regex
+	var regexMatches func(*http.Request) bool
+	if policy.Regex == "" {
+		regexMatches = func(r *http.Request) bool { return true }
+	} else if re, err := regexp.Compile(policy.Regex); err == nil {
+		regexMatches = func(r *http.Request) bool {
+			return re.MatchString(r.URL.Path)
+		}
+	} else {
+		log.Error().Err(err).Str("regex", policy.Regex).Msg("proxy: invalid regex in policy, ignoring route")
+		regexMatches = func(r *http.Request) bool { return false }
+	}
+
+	return func(r *http.Request, rm *mux.RouteMatch) bool {
+		return sourceMatches(r) && prefixMatches(r) && pathMatches(r) && regexMatches(r)
+	}
+}

proxy/proxy_test.go

@@ -276,3 +276,59 @@ func TestNewReverseProxy(t *testing.T) {
 		t.Errorf("got body %q; expected %q", g, e)
 	}
 }
+
+func TestRouteMatcherFuncFromPolicy(t *testing.T) {
+	tests := []struct {
+		source, prefix, path, regex string
+		incomingURL                 string
+		expect                      bool
+		msg                         string
+	}{
+		// host in source
+		{"https://www.example.com", "", "", "",
+			"https://www.example.com", true,
+			"should match when host is the same as source host"},
+		{"https://www.example.com", "", "", "",
+			"https://www.google.com", false,
+			"should not match when host is different from source host"},
+
+		// path prefix in source
+		{"https://www.example.com/admin", "", "", "",
+			"https://www.example.com/admin/someaction", true,
+			"should match when path begins with source path"},
+		{"https://www.example.com/admin", "", "", "",
+			"https://www.example.com/notadmin", false,
+			"should not match when path does not begin with source path"},
+
+		// path prefix
+		{"https://www.example.com", "/admin", "", "",
+			"https://www.example.com/admin/someaction", true,
+			"should match when path begins with prefix"},
+		{"https://www.example.com", "/admin", "", "",
+			"https://www.example.com/notadmin", false,
+			"should not match when path does not begin with prefix"},
+	}
+
+	for _, tt := range tests {
+		srcURL, err := url.Parse(tt.source)
+		if err != nil {
+			panic(err)
+		}
+		src := &config.HostnameURL{URL: srcURL}
+		matcher := routeMatcherFuncFromPolicy(config.Policy{
+			Source: src,
+			Prefix: tt.prefix,
+			Path:   tt.path,
+			Regex:  tt.regex,
+		})
+		req, err := http.NewRequest("GET", tt.incomingURL, nil)
+		if err != nil {
+			panic(err)
+		}
+		actual := matcher(req, nil)
+		if actual != tt.expect {
+			t.Errorf("%s (source=%s prefix=%s path=%s regex=%s incoming-url=%s)",
+				tt.msg, tt.source, tt.prefix, tt.path, tt.regex, tt.incomingURL)
+		}
+	}
+}