Expose TLS placeholders (#2982)

* caddytls: Add CipherSuiteName and ProtocolName functions

The cipher_suites.go file is derived from a commit to the Go master
branch that's slated for Go 1.14.  Once Go 1.14 is released, this file
can be removed.

* caddyhttp: Use commonLogEmptyValue in common_log replacer

* caddyhttp: Add TLS placeholders

* caddytls: update unsupportedProtocols

Don't export unsupportedProtocols and update its godoc to mention that
it's used for logging only.

* caddyhttp: simplify getRegTLSReplacement signature

getRegTLSReplacement should receive a string instead of a pointer.

* caddyhttp: Remove http.request.tls.client.cert replacer

The previous behavior of printing the raw certificate bytes was ported
from Caddy 1, but the usefulness of that approach is suspect.  Remove
the client cert replacer from v2 until a use case is presented.

* caddyhttp: Use tls.CipherSuiteName from Go 1.14

Remove ported version of CipherSuiteName in the process.

1 files changed, 89 insertions, 15 deletions

diff --git a/modules/caddyhttp/replacer.go b/modules/caddyhttp/replacer.go
index cea820d05..c9c7522e7 100644
--- a/modules/caddyhttp/replacer.go
+++ b/modules/caddyhttp/replacer.go
@@ -15,6 +15,9 @@
 package caddyhttp
 
 import (
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
 	"fmt"
 	"net"
 	"net/http"
@@ -24,14 +27,15 @@ import (
 	"strings"
 
 	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/modules/caddytls"
 )
 
 func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.ResponseWriter) {
 	httpVars := func(key string) (string, bool) {
 		if req != nil {
 			// query string parameters
-			if strings.HasPrefix(key, queryReplPrefix) {
-				vals := req.URL.Query()[key[len(queryReplPrefix):]]
+			if strings.HasPrefix(key, reqURIQueryReplPrefix) {
+				vals := req.URL.Query()[key[len(reqURIQueryReplPrefix):]]
 				// always return true, since the query param might
 				// be present only in some requests
 				return strings.Join(vals, ","), true
@@ -47,8 +51,8 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 			}
 
 			// cookies
-			if strings.HasPrefix(key, cookieReplPrefix) {
-				name := key[len(cookieReplPrefix):]
+			if strings.HasPrefix(key, reqCookieReplPrefix) {
+				name := key[len(reqCookieReplPrefix):]
 				for _, cookie := range req.Cookies() {
 					if strings.EqualFold(name, cookie.Name) {
 						// always return true, since the cookie might
@@ -58,6 +62,11 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 				}
 			}
 
+			// http.request.tls.
+			if strings.HasPrefix(key, reqTLSReplPrefix) {
+				return getReqTLSReplacement(req, key)
+			}
+
 			switch key {
 			case "http.request.method":
 				return req.Method, true
@@ -129,8 +138,8 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 			}
 
 			// hostname labels
-			if strings.HasPrefix(key, hostLabelReplPrefix) {
-				idxStr := key[len(hostLabelReplPrefix):]
+			if strings.HasPrefix(key, reqHostLabelsReplPrefix) {
+				idxStr := key[len(reqHostLabelsReplPrefix):]
 				idx, err := strconv.Atoi(idxStr)
 				if err != nil {
 					return "", false
@@ -150,8 +159,8 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 			}
 
 			// path parts
-			if strings.HasPrefix(key, pathPartsReplPrefix) {
-				idxStr := key[len(pathPartsReplPrefix):]
+			if strings.HasPrefix(key, reqURIPathReplPrefix) {
+				idxStr := key[len(reqURIPathReplPrefix):]
 				idx, err := strconv.Atoi(idxStr)
 				if err != nil {
 					return "", false
@@ -208,12 +217,77 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 	repl.Map(httpVars)
 }
 
+func getReqTLSReplacement(req *http.Request, key string) (string, bool) {
+	if req == nil || req.TLS == nil {
+		return "", false
+	}
+
+	if len(key) < len(reqTLSReplPrefix) {
+		return "", false
+	}
+
+	field := strings.ToLower(key[len(reqTLSReplPrefix):])
+
+	if strings.HasPrefix(field, "client.") {
+		cert := getTLSPeerCert(req.TLS)
+		if cert == nil {
+			return "", false
+		}
+
+		switch field {
+		case "client.fingerprint":
+			return fmt.Sprintf("%x", sha256.Sum256(cert.Raw)), true
+		case "client.issuer":
+			return cert.Issuer.String(), true
+		case "client.serial":
+			return fmt.Sprintf("%x", cert.SerialNumber), true
+		case "client.subject":
+			return cert.Subject.String(), true
+		default:
+			return "", false
+		}
+	}
+
+	switch field {
+	case "version":
+		return caddytls.ProtocolName(req.TLS.Version), true
+	case "cipher_suite":
+		return tls.CipherSuiteName(req.TLS.CipherSuite), true
+	case "resumed":
+		if req.TLS.DidResume {
+			return "true", true
+		}
+		return "false", true
+	case "proto":
+		return req.TLS.NegotiatedProtocol, true
+	case "proto_mutual":
+		if req.TLS.NegotiatedProtocolIsMutual {
+			return "true", true
+		}
+		return "false", true
+	case "server_name":
+		return req.TLS.ServerName, true
+	default:
+		return "", false
+	}
+}
+
+// getTLSPeerCert retrieves the first peer certificate from a TLS session.
+// Returns nil if no peer cert is in use.
+func getTLSPeerCert(cs *tls.ConnectionState) *x509.Certificate {
+	if len(cs.PeerCertificates) == 0 {
+		return nil
+	}
+	return cs.PeerCertificates[0]
+}
+
 const (
-	queryReplPrefix      = "http.request.uri.query."
-	reqHeaderReplPrefix  = "http.request.header."
-	cookieReplPrefix     = "http.request.cookie."
-	hostLabelReplPrefix  = "http.request.host.labels."
-	pathPartsReplPrefix  = "http.request.uri.path."
-	varsReplPrefix       = "http.vars."
-	respHeaderReplPrefix = "http.response.header."
+	reqCookieReplPrefix     = "http.request.cookie."
+	reqHeaderReplPrefix     = "http.request.header."
+	reqHostLabelsReplPrefix = "http.request.host.labels."
+	reqTLSReplPrefix        = "http.request.tls."
+	reqURIPathReplPrefix    = "http.request.uri.path."
+	reqURIQueryReplPrefix   = "http.request.uri.query."
+	respHeaderReplPrefix    = "http.response.header."
+	varsReplPrefix          = "http.vars."
 )