feat: auto detect tee env on issuer side (#32)

* feat: auto detect tee env on issuer side

* chore: sets client attestation to none, updates readme

* Update README.md

---------

Co-authored-by: Frieder Paape <frieder@konvera.io>

Author: fnerdman

README.md

@@ -39,10 +39,10 @@ Client
 
 - `--listen-addr`: address to listen on (default: "127.0.0.1:8080")
 - `--target-addr`: address to proxy requests to (default: "https://localhost:80")
-- `--server-attestation-type`: type of attestation to present (none, azure-tdx) (default: "azure-tdx")
+- `--server-attestation-type`: type of attestation to present (none, auto, dcap-tdx, azure-tdx) (default: "auto")
 - `--tls-certificate-path`: Path to certificate (PEM file) to present. Only valid for --server-attestation-type=none and with `--tls-private-key-path`.
 - `--tls-private-key-path`: Path to private key file for the certificate (PEM). Only valid with --tls-certificate-path.
-- `--client-attestation-type`: type of attestation to expect and verify (none, azure-tdx) (default: "none")
+- `--client-attestation-type`: type of attestation to expect and verify (none, dcap-tdx, azure-tdx) (default: "none")
 - `--client-measurements`: optional path to JSON measurements enforced on the client
 - `--log-json`: log in JSON format (default: false)
 - `--log-debug`: log debug messages (default: false)
@@ -70,7 +70,7 @@ sudo ./build/proxy-server --listen-addr=<listen-addr> --target-addr=<target-addr
 docker run -p 8080:8080 -e LOG_JSON=1 cvm-proxy-server
 ```
 
-By default the server will present Azure TDX attestation, and you can modify that via the `--server-attestation-type` flag.
+By default the server will determine the attestation issuer automatically, and you can modify that via the `--server-attestation-type` flag.
 The server can be made to present a regular TLS certificate through `--tls-certificate-path` and `--tls-private-key-path` flags instead of aTLS one.
 
 By default the server will not verify client attestations, you can change that via `--client-attestation-type` and `--client-measurements` flags. Valid for both aTLS and regular TLS.
@@ -89,7 +89,7 @@ This repository contains a [dummy http server](./cmd/dummy-server/main.go) that
 - `--server-measurements`: optional path to JSON measurements enforced on the server
 - `--verify-tls`: verify server's TLS certificate instead of server's attestation. Only valid for server-attestation-type=none.
 - `--tls-ca-certificate`: additional CA certificate to verify against (PEM) [default=no additional TLS certs]. Only valid with --verify-tls.
-- `--client-attestation-type`: type of attestation to present (none, azure-tdx) (default: "none")
+- `--client-attestation-type`: type of attestation to present (none, auto, dcap-tdx, azure-tdx) (default: "none")
 - `--log-json`: log in JSON format (default: false)
 - `--log-debug`: log debug messages (default: false)
 - `--log-dcap-quote`: log dcap quotes to folder quotes/ (default: false)
@@ -111,7 +111,7 @@ make build-proxy-client
 By default the client will expect the server to present an Azure TDX attestation, and you can modify that via the `--server-attestation-type` and  `--server-measurements` flags.
 The server can also be a regular TLS server, which you can configure with the `--verify-tls` flag, which is only valid in combination with `--server-attestation-type=none`. Non-standard CA for the server can also be configured with `--tls-ca-certificate`.
 
-By default the client will not present client attestations, you can change that via `--client-attestation-type` flag. Valid for both aTLS and TLS server proxies.
+By default the client will not present client attestations, you can change that via `--client-attestation-type` flag. If this is set to "auto", it will try to determine the attestation issuer automatically. Valid for both aTLS and TLS server proxies.
 
 This repository contains a sample [measurements.json](./measurements.json) file that you can use. The client will (correctly) complain about unexpected measurements that you can then correct.
 

cmd/proxy-client/main.go

@@ -46,7 +46,7 @@ var flags []cli.Flag = []cli.Flag{
 	&cli.StringFlag{
 		Name:  "client-attestation-type",
 		Value: string(proxy.AttestationNone),
-		Usage: "type of attestation to present (" + proxy.AvailableAttestationTypes + ")",
+		Usage: "type of attestation to present (" + proxy.AvailableAttestationTypes + ").",
 	},
 	&cli.BoolFlag{
 		Name:  "log-json",

cmd/proxy-server/main.go

@@ -40,8 +40,8 @@ var flags []cli.Flag = []cli.Flag{
 	&cli.StringFlag{
 		Name:    "server-attestation-type",
 		EnvVars: []string{"SERVER_ATTESTATION_TYPE"},
-		Value:   string(proxy.AttestationAzureTDX),
-		Usage:   "type of attestation to present (" + proxy.AvailableAttestationTypes + ")",
+		Value:   string(proxy.AttestationAuto),
+		Usage:   "type of attestation to present (" + proxy.AvailableAttestationTypes + "). Defaults to automatic detection.",
 	},
 	&cli.StringFlag{
 		Name:    "tls-certificate-path",

proxy/atls_config.go

@@ -24,16 +24,19 @@ type AttestationType string
 
 const (
 	AttestationNone     AttestationType = "none"
+	AttestationAuto     AttestationType = "auto"
 	AttestationAzureTDX AttestationType = "azure-tdx"
 	AttestationDCAPTDX  AttestationType = "dcap-tdx"
 )
 
-const AvailableAttestationTypes string = "none, azure-tdx, dcap-tdx"
+const AvailableAttestationTypes string = "none, auto, azure-tdx, dcap-tdx"
 
 func ParseAttestationType(attestationType string) (AttestationType, error) {
 	switch attestationType {
 	case string(AttestationNone):
 		return AttestationNone, nil
+	case string(AttestationAuto):
+		return AttestationAuto, nil
 	case string(AttestationAzureTDX):
 		return AttestationAzureTDX, nil
 	case string(AttestationDCAPTDX):
@@ -56,7 +59,31 @@ func CreateAttestationIssuer(log *slog.Logger, attestationType AttestationType)
 	}
 }
 
+// DetectAttestationType determines the attestation type based on environment
+func DetectAttestationType() AttestationType {
+	// Check for TDX device files - these indicate DCAP TDX
+	_, tdxErr1 := os.Stat("/dev/tdx-guest")
+	_, tdxErr2 := os.Stat("/dev/tdx_guest")
+	if tdxErr1 == nil || tdxErr2 == nil {
+		return AttestationDCAPTDX
+	}
+
+	// Try Azure TDX attestation - if it works, we're in Azure TDX
+	issuer := azure_tdx.NewIssuer(nil) // nil logger for detection
+	_, err := issuer.Issue(context.Background(), []byte("test"), []byte("test"))
+	if err == nil {
+		return AttestationAzureTDX
+	}
+
+	return AttestationNone
+}
+
 func CreateAttestationValidators(log *slog.Logger, attestationType AttestationType, jsonMeasurementsPath string) ([]atls.Validator, error) {
+	if attestationType == AttestationAuto {
+                attestationType = DetectAttestationType()
+		log.With("detected_attestation", attestationType).Info("Auto-detected attestation type")
+        }
+
 	if attestationType == AttestationNone {
 		return nil, nil
 	}