caddyhttp: Add client cert SAN placeholders

modules/caddyhttp/app.go

@@ -72,9 +72,15 @@ func init() {
 // `{http.request.tls.proto_mutual}` | The negotiated next protocol was advertised by the server
 // `{http.request.tls.server_name}` | The server name requested by the client, if any
 // `{http.request.tls.client.fingerprint}` | The SHA256 checksum of the client certificate
+// `{http.request.tls.client.public_key}` | The public key of the client certificate.
+// `{http.request.tls.client.public_key_sha256}` | The SHA256 checksum of the client's public key.
 // `{http.request.tls.client.issuer}` | The issuer DN of the client certificate
 // `{http.request.tls.client.serial}` | The serial number of the client certificate
 // `{http.request.tls.client.subject}` | The subject DN of the client certificate
+// `{http.request.tls.client.san.dns_names.*}` | SAN DNS names(index optional)
+// `{http.request.tls.client.san.emails.*}` | SAN email addresses (index optional)
+// `{http.request.tls.client.san.ips.*}` | SAN IP addresses (index optional)
+// `{http.request.tls.client.san.uris.*}` | SAN URIs (index optional)
 // `{http.request.uri.path.*}` | Parts of the path, split by `/` (0-based from left)
 // `{http.request.uri.path.dir}` | The directory, excluding leaf filename
 // `{http.request.uri.path.file}` | The filename of the path, excluding directory

modules/caddyhttp/caddyauth/caddyfile.go

@@ -27,7 +27,7 @@ func init() {
 
 // parseCaddyfile sets up the handler from Caddyfile tokens. Syntax:
 //
-//     basicauth [<matcher>] [<hash_algorithm>] {
+//     basicauth [<matcher>] [<hash_algorithm> [<realm>]] {
 //         <username> <hashed_password_base64> [<salt_base64>]
 //         ...
 //     }

modules/caddyhttp/replacer.go

@@ -28,6 +28,7 @@ import (
 	"net"
 	"net/http"
 	"net/textproto"
+	"net/url"
 	"path"
 	"strconv"
 	"strings"
@@ -163,7 +164,7 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 			if strings.HasPrefix(key, reqHostLabelsReplPrefix) {
 				idxStr := key[len(reqHostLabelsReplPrefix):]
 				idx, err := strconv.Atoi(idxStr)
-				if err != nil {
+				if err != nil || idx < 0 {
 					return "", false
 				}
 				reqHost, _, err := net.SplitHostPort(req.Host)
@@ -171,9 +172,6 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 					reqHost = req.Host // OK; assume there was no port
 				}
 				hostLabels := strings.Split(reqHost, ".")
-				if idx < 0 {
-					return "", false
-				}
 				if idx > len(hostLabels) {
 					return "", true
 				}
@@ -245,6 +243,64 @@ func getReqTLSReplacement(req *http.Request, key string) (interface{}, bool) {
 			return nil, false
 		}
 
+		// subject alternate names (SANs)
+		if strings.HasPrefix(field, "client.san.") {
+			field = field[len("client.san."):]
+			var fieldName string
+			var fieldValue interface{}
+			switch {
+			case strings.HasPrefix(field, "dns_names"):
+				fieldName = "dns_names"
+				fieldValue = cert.DNSNames
+			case strings.HasPrefix(field, "emails"):
+				fieldName = "emails"
+				fieldValue = cert.EmailAddresses
+			case strings.HasPrefix(field, "ips"):
+				fieldName = "ips"
+				fieldValue = cert.IPAddresses
+			case strings.HasPrefix(field, "uris"):
+				fieldName = "uris"
+				fieldValue = cert.URIs
+			default:
+				return nil, false
+			}
+			field = field[len(fieldName):]
+
+			// if no index was specified, return the whole list
+			if field == "" {
+				return fieldValue, true
+			}
+			if len(field) < 2 || field[0] != '.' {
+				return nil, false
+			}
+			field = field[1:] // trim '.' between field name and index
+
+			// get the numeric index
+			idx, err := strconv.Atoi(field)
+			if err != nil || idx < 0 {
+				return nil, false
+			}
+
+			// access the indexed element and return it
+			switch v := fieldValue.(type) {
+			case []string:
+				if idx >= len(v) {
+					return nil, true
+				}
+				return v[idx], true
+			case []net.IP:
+				if idx >= len(v) {
+					return nil, true
+				}
+				return v[idx], true
+			case []*url.URL:
+				if idx >= len(v) {
+					return nil, true
+				}
+				return v[idx], true
+			}
+		}
+
 		switch field {
 		case "client.fingerprint":
 			return fmt.Sprintf("%x", sha256.Sum256(cert.Raw)), true

modules/caddyhttp/replacer_test.go

@@ -147,6 +147,26 @@ eqp31wM9il1n+guTNyxJd+FzVAH+hCZE5K+tCgVDdVFUlDEHHbS/wqb2PSIoouLV
 			input:  "{http.request.tls.client.subject}",
 			expect: "CN=client.localdomain",
 		},
+		{
+			input:  "{http.request.tls.client.san.dns_names}",
+			expect: "[localhost]",
+		},
+		{
+			input:  "{http.request.tls.client.san.dns_names.0}",
+			expect: "localhost",
+		},
+		{
+			input:  "{http.request.tls.client.san.dns_names.1}",
+			expect: "<empty>",
+		},
+		{
+			input:  "{http.request.tls.client.san.ips}",
+			expect: "[127.0.0.1]",
+		},
+		{
+			input:  "{http.request.tls.client.san.ips.0}",
+			expect: "127.0.0.1",
+		},
 	} {
 		actual := repl.ReplaceAll(tc.input, "<empty>")
 		if actual != tc.expect {