Move bundle & sign related ELF operations to elf.go

ego/cli/elf.go

@@ -0,0 +1,129 @@
+// Copyright (c) Edgeless Systems GmbH.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package cli
+
+import (
+	"debug/elf"
+	"encoding/binary"
+	"errors"
+	"io"
+	"os"
+)
+
+func (c *Cli) embedConfigAsPayload(path string, jsonData []byte) error {
+	// Load ELF executable
+	f, err := c.fs.OpenFile(path, os.O_RDWR, 0)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	// Check if a payload already exists
+	payloadSize, payloadOffset, oeInfoOffset, err := getPayloadInformation(f)
+	if err != nil {
+		return err
+	}
+
+	// If a payload already exists, truncate the file to remove it
+	if payloadSize > 0 {
+		fileStat, err := f.Stat()
+		if err != nil {
+			return err
+		}
+
+		// Check if payload is at expected location
+		expectedPayloadOffset := fileStat.Size() - int64(payloadSize)
+		if expectedPayloadOffset != payloadOffset {
+			return errors.New("expected payload location does not match real payload location, cannot safely truncate old payload")
+		}
+
+		err = f.Truncate(payloadOffset)
+		if err != nil {
+			return err
+		}
+	} else if (payloadSize == 0) != (payloadOffset == 0) {
+		return errors.New("payload information in header is inconsistent, cannot continue")
+	}
+
+	// Get current file size to determine offset
+	fileStat, err := f.Stat()
+	if err != nil {
+		return err
+	}
+	filesize := fileStat.Size()
+
+	// Write payload offset and size to .oeinfo header
+	if err := writeUint64At(f, uint64(filesize), oeInfoOffset+2048); err != nil {
+		return err
+	}
+	if err := writeUint64At(f, uint64(len(jsonData)), oeInfoOffset+2056); err != nil {
+		return err
+	}
+
+	// And finally, append the payload to the file
+	n, err := f.WriteAt(jsonData, filesize)
+	if err != nil {
+		return err
+	} else if n != len(jsonData) {
+		return errors.New("failed to embed enclave.json as metadata")
+	}
+
+	return nil
+}
+
+func getPayloadInformation(f io.ReaderAt) (uint64, int64, int64, error) {
+	// .oeinfo + 2056 contains the size of an embedded Edgeless RT data payload.
+	// If it is > 0, a payload already exists.
+
+	elfFile, err := elf.NewFile(f)
+	if err != nil {
+		return 0, 0, 0, err
+	}
+
+	oeInfo := elfFile.Section(".oeinfo")
+	if oeInfo == nil {
+		return 0, 0, 0, ErrNoOEInfo
+	}
+
+	payloadOffset, err := readUint64At(oeInfo, 2048)
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	payloadSize, err := readUint64At(oeInfo, 2056)
+	if err != nil {
+		return 0, 0, 0, err
+	}
+
+	return payloadSize, int64(payloadOffset), int64(oeInfo.Offset), nil
+}
+
+func writeUint64At(w io.WriterAt, x uint64, off int64) error {
+	xByte := make([]byte, 8)
+	binary.LittleEndian.PutUint64(xByte, x)
+
+	n, err := w.WriteAt(xByte, off)
+	if err != nil {
+		return err
+	} else if n != 8 {
+		return errors.New("did not write expected number of bytes")
+	}
+
+	return nil
+}
+
+func readUint64At(r io.ReaderAt, off int64) (uint64, error) {
+	xByte := make([]byte, 8)
+
+	n, err := r.ReadAt(xByte, off)
+	if err != nil {
+		return 0, err
+	} else if n != 8 {
+		return 0, errors.New("did not read expected number of bytes")
+	}
+
+	return binary.LittleEndian.Uint64(xByte), nil
+}

ego/cli/elf_test.go

@@ -0,0 +1,151 @@
+// Copyright (c) Edgeless Systems GmbH.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package cli
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+
+	"ego/config"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// create an unsigned EGo executable
+var elfUnsigned = func() []byte {
+	const outFile = "hello"
+	const srcFile = outFile + ".go"
+
+	goroot, err := filepath.Abs(filepath.Join("..", "..", "_ertgo"))
+	if err != nil {
+		panic(err)
+	}
+
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		panic(err)
+	}
+	defer os.RemoveAll(dir)
+
+	// write minimal source file
+	const src = `package main;import _"time";func main(){}`
+	if err := ioutil.WriteFile(filepath.Join(dir, srcFile), []byte(src), 0o400); err != nil {
+		panic(err)
+	}
+
+	// compile
+	cmd := exec.Command(filepath.Join(goroot, "bin", "go"), "build", srcFile)
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "GOROOT="+goroot)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		panic(err)
+	}
+
+	// read resulting executable
+	data, err := ioutil.ReadFile(filepath.Join(dir, outFile))
+	if err != nil {
+		panic(err)
+	}
+
+	return data
+}()
+
+func TestEmbedConfigAsPayload(t *testing.T) {
+	require := require.New(t)
+	assert := assert.New(t)
+
+	// Setup test environment
+	fs := afero.Afero{Fs: afero.NewMemMapFs()}
+	runner := signRunner{fs: fs}
+	cli := NewCli(&runner, fs)
+
+	// Copy from hostfs to memfs
+	const exe = "helloworld"
+	require.NoError(fs.WriteFile(exe, elfUnsigned, 0))
+
+	// Check if no payload exists
+	unsignedExeMemfs, err := fs.Open(exe)
+	require.NoError(err)
+	unsignedExeMemfsStat, err := unsignedExeMemfs.Stat()
+	require.NoError(err)
+	unsignedExeMemfsSize := unsignedExeMemfsStat.Size()
+	payloadSize, payloadOffset, oeInfoOffset, err := getPayloadInformation(unsignedExeMemfs)
+	assert.NoError(err)
+	assert.Zero(payloadSize)
+	assert.Zero(payloadOffset)
+	assert.NotZero(oeInfoOffset)
+	unsignedExeMemfs.Close()
+
+	// Create a default config we want to check
+	testConf := &config.Config{
+		Exe:             exe,
+		Key:             defaultPrivKeyFilename,
+		Debug:           true,
+		HeapSize:        512, //[MB]
+		ProductID:       1,
+		SecurityVersion: 1,
+	}
+
+	// Marshal config
+	jsonData, err := json.Marshal(testConf)
+	require.NoError(err)
+	expectedLengthOfPayload := len(jsonData)
+
+	// Embed json config to helloworld
+	err = cli.embedConfigAsPayload(exe, jsonData)
+	assert.NoError(err)
+
+	// Check if new helloworld_signed now contains signed data
+	signedExeMemfs, err := fs.Open(exe)
+	require.NoError(err)
+	defer signedExeMemfs.Close()
+
+	payloadSize, payloadOffset, oeInfoOffset, err = getPayloadInformation(signedExeMemfs)
+	assert.NoError(err)
+	assert.EqualValues(expectedLengthOfPayload, payloadSize)
+	assert.EqualValues(unsignedExeMemfsSize, payloadOffset)
+	assert.NotZero(oeInfoOffset)
+
+	// Reconstruct the JSON and check equality
+	reconstructedJSON := make([]byte, payloadSize)
+	n, err := signedExeMemfs.ReadAt(reconstructedJSON, payloadOffset)
+	require.NoError(err)
+	require.EqualValues(payloadSize, n)
+	assert.EqualValues(jsonData, reconstructedJSON)
+
+	// Now modify the config, redo everything and see if trucate worked fine and everything still lines up
+	testConf.HeapSize = 5120
+	jsonNewData, err := json.Marshal(testConf)
+	require.NoError(err)
+	expectedLengthOfNewPayload := len(jsonNewData)
+
+	// Re-sign the already signed executable
+	err = cli.embedConfigAsPayload(exe, jsonNewData)
+	assert.NoError(err)
+	payloadSize, payloadOffset, _, err = getPayloadInformation(signedExeMemfs)
+	require.NoError(err)
+	assert.EqualValues(expectedLengthOfNewPayload, payloadSize)
+	assert.EqualValues(unsignedExeMemfsSize, payloadOffset)
+
+	// Reconstruct the JSON and check if it not the old one, but the new one
+	reconstructedJSON = make([]byte, payloadSize)
+	n, err = signedExeMemfs.ReadAt(reconstructedJSON, payloadOffset)
+	require.NoError(err)
+	require.EqualValues(payloadSize, n)
+
+	// Finally, check if we got the new JSON config and not the old one
+	assert.NotEqualValues(jsonData, reconstructedJSON)
+	assert.EqualValues(jsonNewData, reconstructedJSON)
+}