Feat/pcr yaml output (#222)

* remove extra output and provide yaml option
* Add some explanation on how yaml format could be used.

hack/pcr-reader/.gitignore

@@ -0,0 +1 @@
+pcr-reader

hack/pcr-reader/README.md

@@ -88,6 +88,17 @@ PCRs:
 }
 ```
 
+### Extend Config
+
+To set measurement values in Constellation config, use `yaml` format option.
+Optionally filter down results measurements per cloud provider:
+
+Azure
+
+```bash
+./pcr-reader --coord-ip ${COORD_IP} --format yaml | yq e 'del(.[0,6,10,11,12,13,14,15,16,17,18,19,20,21,22,23])' -
+```
+
 ## Meaning of PCR values
 
 An overview about what data is measured into the different registers can be found [in the TPM spec](https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClient_PFP_r1p05_v23_pub.pdf#%5B%7B%22num%22%3A157%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22XYZ%22%7D%2C33%2C400%2C0%5D).

hack/pcr-reader/main.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -25,12 +26,14 @@ import (
 	"github.com/spf13/afero"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
+	"gopkg.in/yaml.v3"
 )
 
 var (
 	coordIP         = flag.String("coord-ip", "", "IP of the VM the Coordinator is running on")
 	coordinatorPort = flag.String("coord-port", "9000", "Port of the Coordinator's pub API")
 	export          = flag.String("o", "", "Write PCRs, formatted as Go code, to file")
+	format          = flag.String("format", "json", "Output format: json, yaml (default json)")
 	quiet           = flag.Bool("q", false, "Set to disable output")
 	timeout         = flag.Duration("timeout", 2*time.Minute, "Wait this duration for the Coordinator to become available")
 )
@@ -38,7 +41,6 @@ var (
 func main() {
 	flag.Parse()
 
-	fmt.Printf("connecting to Coordinator at %s:%s\n", *coordIP, *coordinatorPort)
 	addr := net.JoinHostPort(*coordIP, *coordinatorPort)
 	ctx, cancel := context.WithTimeout(context.Background(), *timeout)
 	defer cancel()
@@ -71,7 +73,7 @@ func main() {
 	}
 
 	if !*quiet {
-		if err := printPCRs(os.Stdout, pcrs); err != nil {
+		if err := printPCRs(os.Stdout, pcrs, *format); err != nil {
 			log.Fatal(err)
 		}
 	}
@@ -82,6 +84,20 @@ func main() {
 	}
 }
 
+type Measurements map[uint32][]byte
+
+// MarshalYAML forces that measurements are written as base64. Default would
+// be to print list of bytes.
+func (m Measurements) MarshalYAML() (interface{}, error) {
+	base64Map := make(map[uint32]string)
+
+	for key, value := range m {
+		base64Map[key] = base64.StdEncoding.EncodeToString(value[:])
+	}
+
+	return base64Map, nil
+}
+
 // connectToCoordinator connects to the Constellation Coordinator and returns its attestation document.
 func connectToCoordinator(ctx context.Context, addr string, tlsConfig *tls.Config) error {
 	conn, err := grpc.DialContext(
@@ -145,12 +161,33 @@ func validatePCRAttDoc(attDocRaw []byte) (map[uint32][]byte, error) {
 }
 
 // printPCRs formates and prints PCRs to the given writer.
-func printPCRs(w io.Writer, pcrs map[uint32][]byte) error {
+// format can be one of 'json' or 'yaml'. If it doesnt match defaults to 'json'.
+func printPCRs(w io.Writer, pcrs map[uint32][]byte, format string) error {
+	switch format {
+	case "json":
+		return printPCRsJSON(w, pcrs)
+	case "yaml":
+		return printPCRsYAML(w, pcrs)
+	default:
+		return printPCRsJSON(w, pcrs)
+	}
+}
+
+func printPCRsYAML(w io.Writer, pcrs Measurements) error {
+	pcrYAML, err := yaml.Marshal(pcrs)
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(w, "%s", string(pcrYAML))
+	return nil
+}
+
+func printPCRsJSON(w io.Writer, pcrs map[uint32][]byte) error {
 	pcrJSON, err := json.MarshalIndent(pcrs, "", "  ")
 	if err != nil {
 		return err
 	}
-	fmt.Fprintf(w, "PCRs:\n%s\n", string(pcrJSON))
+	fmt.Fprintf(w, "%s", string(pcrJSON))
 	return nil
 }
 

hack/pcr-reader/main_test.go

@@ -227,20 +227,48 @@ func mustMarshalAttDoc(t *testing.T, attDoc vtpm.AttestationDocument) []byte {
 }
 
 func TestPrintPCRs(t *testing.T) {
-	assert := assert.New(t)
-
-	pcrs := map[uint32][]byte{
-		0: {0x1, 0x2, 0x3},
-		1: {0x1, 0x2, 0x3},
-		2: {0x1, 0x2, 0x3},
+	testCases := map[string]struct {
+		pcrs   map[uint32][]byte
+		format string
+	}{
+		"json": {
+			pcrs: map[uint32][]byte{
+				0: {0x1, 0x2, 0x3},
+				1: {0x1, 0x2, 0x3},
+				2: {0x1, 0x2, 0x3},
+			},
+			format: "json",
+		},
+		"empty format": {
+			pcrs: map[uint32][]byte{
+				0: {0x1, 0x2, 0x3},
+				1: {0x1, 0x2, 0x3},
+				2: {0x1, 0x2, 0x3},
+			},
+			format: "",
+		},
+		"yaml": {
+			pcrs: map[uint32][]byte{
+				0: {0x1, 0x2, 0x3},
+				1: {0x1, 0x2, 0x3},
+				2: {0x1, 0x2, 0x3},
+			},
+			format: "yaml",
+		},
 	}
 
-	var out bytes.Buffer
-	err := printPCRs(&out, pcrs)
-	assert.NoError(err)
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			assert := assert.New(t)
 
-	for idx, pcr := range pcrs {
-		assert.Contains(out.String(), fmt.Sprintf("\"%d\": ", idx))
-		assert.Contains(out.String(), fmt.Sprintf(": \"%s\"", base64.StdEncoding.EncodeToString(pcr)))
+			var out bytes.Buffer
+			err := printPCRs(&out, tc.pcrs, tc.format)
+			assert.NoError(err)
+
+			for idx, pcr := range tc.pcrs {
+				assert.Contains(out.String(), fmt.Sprintf("%d", idx))
+				assert.Contains(out.String(), base64.StdEncoding.EncodeToString(pcr))
+			}
+		})
 	}
 }