Merge pull request #32 from Amnesic-Systems/improve-verify-tool

Handle all of attestation in `veil-verify`.

.gitignore

@@ -1,6 +1,7 @@
 .vscode
 cmd/veil/veil
+cmd/veil-verify/veil-verify
 cover.html
 cover.out
-veil.tar
-veil.eif
+*.tar
+*.eif

Makefile

@@ -1,5 +1,7 @@
 prog = veil
 prog_dir = cmd/veil
+verify_prog = veil-verify
+verify_prog_dir = cmd/veil-verify
 godeps = go.mod go.sum $(shell find cmd internal -name "*.go" -type f)
 
 image_tag := $(prog)
@@ -81,10 +83,15 @@ $(prog): $(godeps)
 		-ldflags="-s -w" \
 		-buildvcs=false \
 		-o $(prog)
-	@echo "$(prog_dir)/$(prog)"
+	@-sha1sum "$(prog_dir)/$(prog)"
+
+$(verify_prog): $(godeps)
+	@go build -C $(verify_prog_dir) -o $(verify_prog)
+	@-sha1sum "$(verify_prog_dir)/$(verify_prog)"
 
 .PHONY: clean
 clean:
 	rm -f $(prog_dir)/$(prog)
+	rm -f $(verify_prog_dir)/$(verify_prog)
 	rm -f $(cover_out) $(cover_html)
 	rm -f $(image_tar) $(image_eif)

cmd/veil-verify/attestation.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha512"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"strings"
+
+	"github.com/fatih/color"
+
+	"github.com/Amnesic-Systems/veil/internal/enclave"
+	"github.com/Amnesic-Systems/veil/internal/enclave/nitro"
+	"github.com/Amnesic-Systems/veil/internal/enclave/noop"
+	"github.com/Amnesic-Systems/veil/internal/errs"
+	"github.com/Amnesic-Systems/veil/internal/httpx"
+	"github.com/Amnesic-Systems/veil/internal/nonce"
+	"github.com/Amnesic-Systems/veil/internal/util"
+)
+
+var (
+	errFailedToAttest  = errors.New("failed to attest enclave")
+	errFailedToConvert = errors.New("failed to convert measurements to PCR")
+)
+
+func attestEnclave(
+	ctx context.Context,
+	cfg *config,
+	pcrs enclave.PCR,
+) (err error) {
+	defer errs.WrapErr(&err, errFailedToAttest)
+
+	// Generate a nonce to ensure that the attestation document is fresh.
+	nonce, err := nonce.New()
+	if err != nil {
+		return err
+	}
+
+	// Request the enclave's attestation document.  We don't verify HTTPS
+	// certificates because authentication is happening via the attestation
+	// document.
+	client := httpx.NewUnauthClient()
+	url := cfg.addr + "/enclave/attestation?nonce=" + nonce.URLEncode()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return err
+	}
+	resp, err := client.Do(req)
+	if err != nil {
+		return err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("got status %d from enclave", resp.StatusCode)
+	}
+
+	// Parse the attestation document.
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	var rawDoc enclave.RawDocument
+	if err := json.Unmarshal(body, &rawDoc); err != nil {
+		return err
+	}
+
+	// Verify the attestation document, which provides assurance that we are
+	// talking to an enclave.  The nonce provides assurance that we are talking
+	// to an alive enclave (instead of a replayed attestation document).
+	var attester enclave.Attester = nitro.NewAttester()
+	if cfg.testing {
+		attester = noop.NewAttester()
+	}
+	doc, err := attester.Verify(&rawDoc, nonce)
+	if err != nil {
+		return err
+	}
+
+	// Delete empty PCR values from the attestation document.  This is not
+	// ideal; we should either have the rest of the code tolerate empty PCR
+	// values or fix the nsm package, so it doesn't return empty PCR values.
+	empty := make([]byte, sha512.Size384)
+	for i, pcr := range doc.PCRs {
+		if bytes.Equal(pcr, empty) {
+			delete(doc.PCRs, i)
+		}
+	}
+
+	// Verify the attestation document's PCR values, which provide assurance
+	// that the remote enclave's image and kernel match the local copy.
+	if !pcrs.Equal(doc.PCRs) {
+		log.Printf("Expected PCRs:\n%sbut got PCRs:\n%s", pcrs, doc.PCRs)
+		color.Red("Enclave's code DOES NOT match local code!")
+	} else {
+		color.Green("Enclave's code matches local code!")
+	}
+
+	return nil
+}
+
+func toPCR(jsonMsmts []byte) (_ enclave.PCR, err error) {
+	defer errs.WrapErr(&err, errFailedToConvert)
+
+	// This structs represents the JSON-encoded measurements of the enclave
+	// image.  The JSON tags must match the output of the nitro-cli command
+	// line tool. An example:
+	//
+	//	{
+	//	  "Measurements": {
+	//	    "HashAlgorithm": "Sha384 { ... }",
+	//	    "PCR0": "8b927cf0bbf2d668a8c24c69afd23bff2dda713b4f0d70195205950f9a5a1fbb7089ad937e3025ee8d5a084f3d6c9126",
+	//	    "PCR1": "4b4d5b3661b3efc12920900c80e126e4ce783c522de6c02a2a5bf7af3a2b9327b86776f188e4be1c1c404a129dbda493",
+	//	    "PCR2": "22d2194eb27a7cda42e66dd5b91ef13e5a153d797c04ae179e59bef1c93438d6ad0365c175c119230e36d0f8d6b6b59e"
+	//	  }
+	//	}
+	m := struct {
+		Measurements struct {
+			HashAlgorithm string `json:"HashAlgorithm"`
+			PCR0          string `json:"PCR0"`
+			PCR1          string `json:"PCR1"`
+			PCR2          string `json:"PCR2"`
+		} `json:"Measurements"`
+	}{}
+	if err := json.Unmarshal(jsonMsmts, &m); err != nil {
+		return nil, err
+	}
+
+	const want = "sha384"
+	got := strings.ToLower(m.Measurements.HashAlgorithm)
+	if !strings.HasPrefix(got, want) {
+		return nil, fmt.Errorf("expected hash algorithm %q but got %q", want, got)
+	}
+
+	return enclave.PCR{
+		0: util.Must(hex.DecodeString(m.Measurements.PCR0)),
+		1: util.Must(hex.DecodeString(m.Measurements.PCR1)),
+		2: util.Must(hex.DecodeString(m.Measurements.PCR2)),
+	}, nil
+}

cmd/veil-verify/attestation_test.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/Amnesic-Systems/veil/internal/enclave"
+	"github.com/stretchr/testify/require"
+)
+
+func TestToPCR(t *testing.T) {
+	cases := []struct {
+		name     string
+		in       []byte
+		wantPCRs enclave.PCR
+		wantErr  bool
+	}{
+		{
+			name:    "invalid json",
+			in:      []byte("invalid"),
+			wantErr: true,
+		},
+		{
+			name: "invalid hash",
+			in: []byte(`{
+				"Measurements": {
+					"HashAlgorithm": "Sha512 { ... }",
+					"PCR0": "616161616161616161616161616161616161616161616161616161616161616161616161616161616161616161616161",
+					"PCR1": "626262626262626262626262626262626262626262626262626262626262626262626262626262626262626262626262",
+					"PCR2": "636363636363636363636363636363636363636363636363636363636363636363636363636363636363636363636363"
+				}
+			}`),
+			wantErr: true,
+		},
+		{
+			name: "invalid PCR value",
+			in: []byte(`{
+				"Measurements": {
+					"HashAlgorithm": "Sha512 { ... }",
+					"PCR0": "foobar",
+				}
+			}`),
+			wantErr: true,
+		},
+		{
+			name: "valid",
+			in:   []byte(validPCRs),
+			wantPCRs: enclave.PCR{
+				0: []byte("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
+				1: []byte("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"),
+				2: []byte("cccccccccccccccccccccccccccccccccccccccccccccccc"),
+			},
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			gotPCRs, err := toPCR(c.in)
+			require.Equal(t, c.wantErr, err != nil)
+			require.True(t, gotPCRs.Equal(c.wantPCRs))
+		})
+	}
+}