Merge pull request #391 from databacker/encrypted-config-support

deitch · web-flow · commit 896c1d406e5b · 2024-12-08T13:34:46.000+01:00
support for encrypted config
diff --git a/go.mod b/go.mod
@@ -31,7 +31,7 @@ require (
 )
 
 require (
-	github.com/databacker/api/go/api v0.0.0-20241128084006-ed33dc044eaa
+	github.com/databacker/api/go/api v0.0.0-20241202154620-01b0380f21cb
 	github.com/google/go-cmp v0.6.0
 	go.opentelemetry.io/otel v1.31.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp v1.19.0
diff --git a/go.sum b/go.sum
@@ -72,6 +72,12 @@ github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfc
 github.com/cpuguy83/go-md2man/v2 v2.0.3/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
 github.com/databacker/api/go/api v0.0.0-20241128084006-ed33dc044eaa h1:cDI48+AG1mPMdvgGWz/SLpNKhzDiGZwfSSww9VvvWuI=
 github.com/databacker/api/go/api v0.0.0-20241128084006-ed33dc044eaa/go.mod h1:bQhbl71Lk1ATni0H+u249hjoQ8ShAdVNcNjnw6z+SbE=
+github.com/databacker/api/go/api v0.0.0-20241201124314-f86f0bf46c54 h1:NirzpOdczBCCwBlmfdYLcroaFYIdR2bJkeDjwJKaxQE=
+github.com/databacker/api/go/api v0.0.0-20241201124314-f86f0bf46c54/go.mod h1:bQhbl71Lk1ATni0H+u249hjoQ8ShAdVNcNjnw6z+SbE=
+github.com/databacker/api/go/api v0.0.0-20241201140600-cb4443d89ac3 h1:RhB+NKRnj6T+2mbmvy1me2zglATss01byA9Nar+0pbk=
+github.com/databacker/api/go/api v0.0.0-20241201140600-cb4443d89ac3/go.mod h1:bQhbl71Lk1ATni0H+u249hjoQ8ShAdVNcNjnw6z+SbE=
+github.com/databacker/api/go/api v0.0.0-20241202154620-01b0380f21cb h1:9PthuA+o1wBZuTkNc2LLXQfI5+Myy+ok8nD3bQzd7DA=
+github.com/databacker/api/go/api v0.0.0-20241202154620-01b0380f21cb/go.mod h1:bQhbl71Lk1ATni0H+u249hjoQ8ShAdVNcNjnw6z+SbE=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
diff --git a/pkg/config/process.go b/pkg/config/process.go
@@ -1,11 +1,20 @@
 package config
 
 import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/ecdh"
+	"crypto/ed25519"
+	"crypto/sha256"
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"io"
 
 	"github.com/databacker/api/go/api"
+	"golang.org/x/crypto/chacha20poly1305"
+	"golang.org/x/crypto/hkdf"
+	"golang.org/x/crypto/nacl/box"
 	"gopkg.in/yaml.v3"
 
 	"github.com/databacker/mysql-backup/pkg/remote"
@@ -15,7 +24,10 @@ import (
 // If the configuration is of type remote, it will retrieve the remote configuration.
 // Continues to process remotes until it gets a final valid ConfigSpec or fails.
 func ProcessConfig(r io.Reader) (actualConfig *api.ConfigSpec, err error) {
-	var conf api.Config
+	var (
+		conf        api.Config
+		credentials []string
+	)
 	decoder := yaml.NewDecoder(r)
 	if err := decoder.Decode(&conf); err != nil {
 		return nil, fmt.Errorf("fatal error reading config file: %w", err)
@@ -60,6 +72,20 @@ func ProcessConfig(r io.Reader) (actualConfig *api.ConfigSpec, err error) {
 				return nil, fmt.Errorf("error parsing remote config: %w", err)
 			}
 			conf = remoteConfig
+			// save encryption key for later
+			if spec.Credentials != nil {
+				credentials = append(credentials, *spec.Credentials)
+			}
+		case api.Encrypted:
+			var spec api.EncryptedSpec
+			if err := yaml.Unmarshal(specBytes, &spec); err != nil {
+				return nil, fmt.Errorf("parsed yaml had kind encrypted, but spec invalid")
+			}
+			// now try to decrypt it
+			conf, err = decryptConfig(spec, credentials)
+			if err != nil {
+				return nil, fmt.Errorf("error decrypting config: %w", err)
+			}
 		default:
 			return nil, fmt.Errorf("unknown config type: %s", conf.Kind)
 		}
@@ -91,3 +117,121 @@ func getRemoteConfig(spec api.RemoteSpec) (conf api.Config, err error) {
 
 	return baseConf, nil
 }
+
+// decryptConfig decrypt an EncryptedSpec given an EncryptedSpec and a list of credentials.
+// Returns the decrypted Config struct.
+func decryptConfig(spec api.EncryptedSpec, credentials []string) (api.Config, error) {
+	var plainConfig api.Config
+	if spec.Algorithm == nil {
+		return plainConfig, errors.New("empty algorithm")
+	}
+	if spec.RecipientPublicKey == nil {
+		return plainConfig, errors.New("empty recipient public key")
+	}
+	if spec.SenderPublicKey == nil {
+		return plainConfig, errors.New("empty sender public key")
+	}
+	if spec.Data == nil {
+		return plainConfig, errors.New("empty data")
+	}
+	// make sure we have the key matching the public key
+	var (
+		privateKey *ecdh.PrivateKey
+		curve      = ecdh.X25519()
+	)
+
+	for _, cred := range credentials {
+		// get our curve25519 private key
+		keyBytes, err := base64.StdEncoding.DecodeString(cred)
+		if err != nil {
+			return plainConfig, fmt.Errorf("error decoding credentials: %w", err)
+		}
+		if len(keyBytes) != ed25519.SeedSize {
+			return plainConfig, fmt.Errorf("invalid key size %d, must be %d", len(keyBytes), ed25519.SeedSize)
+		}
+		candidatePrivateKey, err := curve.NewPrivateKey(keyBytes)
+		if err != nil {
+			return plainConfig, fmt.Errorf("error creating private key: %w", err)
+		}
+		// get the public key from the private key
+		candidatePublicKey := candidatePrivateKey.PublicKey()
+		// check if the public key matches the one we have, if so, break
+		pubKeyBase64 := base64.StdEncoding.EncodeToString(candidatePublicKey.Bytes())
+		if pubKeyBase64 == *spec.RecipientPublicKey {
+			privateKey = candidatePrivateKey
+			break
+		}
+	}
+	// if we didn't find a matching key, return an error
+	if privateKey == nil {
+		return plainConfig, fmt.Errorf("no private key found that matches public key %s", *spec.RecipientPublicKey)
+	}
+	senderPublicKeyBytes, err := base64.StdEncoding.DecodeString(*spec.SenderPublicKey)
+	if err != nil {
+		return plainConfig, fmt.Errorf("failed to decode sender public key: %w", err)
+	}
+
+	// Derive the shared secret using the sender's public key and receiver's private key
+	var senderPublicKey, receiverPrivateKey, sharedSecret [32]byte
+	copy(senderPublicKey[:], senderPublicKeyBytes)
+	copy(receiverPrivateKey[:], privateKey.Bytes()) // Use the seed to get the private scalar
+	box.Precompute(&sharedSecret, &senderPublicKey, &receiverPrivateKey)
+
+	// Derive a symmetric key using HKDF with the shared secret
+	hkdfReader := hkdf.New(sha256.New, sharedSecret[:], nil, []byte(api.SymmetricKey))
+	var symmetricKeySize int
+	switch *spec.Algorithm {
+	case api.AesGcm256:
+		symmetricKeySize = 32
+	case api.Chacha20Poly1305:
+		symmetricKeySize = 32
+	default:
+		return plainConfig, fmt.Errorf("unsupported algorithm: %s", *spec.Algorithm)
+	}
+	symmetricKey := make([]byte, symmetricKeySize)
+	if _, err := hkdfReader.Read(symmetricKey); err != nil {
+		return plainConfig, fmt.Errorf("failed to derive symmetric key: %w", err)
+	}
+
+	var (
+		plaintext []byte
+		aead      cipher.AEAD
+	)
+	encryptedData, err := base64.StdEncoding.DecodeString(*spec.Data)
+	if err != nil {
+		return plainConfig, fmt.Errorf("failed to decode encrypted data: %w", err)
+	}
+	switch *spec.Algorithm {
+	case api.AesGcm256:
+		// Decrypt with AES-GCM
+		block, err := aes.NewCipher(symmetricKey)
+		if err != nil {
+			return plainConfig, fmt.Errorf("failed to initialize AES cipher: %w", err)
+		}
+		aead, err = cipher.NewGCM(block)
+		if err != nil {
+			return plainConfig, fmt.Errorf("failed to initialize AES-GCM: %w", err)
+		}
+	case api.Chacha20Poly1305:
+		// Decrypt with ChaCha20Poly1305
+		aead, err = chacha20poly1305.New(symmetricKey)
+		if err != nil {
+			return plainConfig, fmt.Errorf("failed to initialize ChaCha20Poly1305: %w", err)
+		}
+	default:
+		return plainConfig, fmt.Errorf("unsupported algorithm: %s", *spec.Algorithm)
+	}
+	if len(encryptedData) < aead.NonceSize() {
+		return plainConfig, errors.New("invalid encrypted data length")
+	}
+	dataNonce := encryptedData[:aead.NonceSize()]
+	ciphertext := encryptedData[aead.NonceSize():]
+	plaintext, err = aead.Open(nil, dataNonce, ciphertext, nil)
+	if err != nil {
+		return plainConfig, fmt.Errorf("failed to decrypt data: %w", err)
+	}
+	if err := yaml.Unmarshal(plaintext, &plainConfig); err != nil {
+		return plainConfig, fmt.Errorf("parsed yaml had kind remote, but spec invalid")
+	}
+	return plainConfig, nil
+}
diff --git a/pkg/config/process_test.go b/pkg/config/process_test.go
@@ -2,13 +2,23 @@ package config
 
 import (
 	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/ecdh"
+	"crypto/ed25519"
+	cryptorand "crypto/rand"
+	"crypto/sha256"
 	"encoding/base64"
+	"errors"
+	"io"
 	"net/http"
 	"os"
 	"strings"
 	"testing"
 
 	utiltest "github.com/databacker/mysql-backup/pkg/internal/test"
+	"golang.org/x/crypto/hkdf"
+	"golang.org/x/crypto/nacl/box"
 	"gopkg.in/yaml.v3"
 
 	"github.com/databacker/api/go/api"
@@ -88,3 +98,147 @@ func TestGetRemoteConfig(t *testing.T) {
 	}
 
 }
+
+func TestDecryptConfig(t *testing.T) {
+	configFile := "./testdata/config.yml"
+	content, err := os.ReadFile(configFile)
+	if err != nil {
+		t.Fatalf("failed to read config file: %v", err)
+	}
+	var validConfig api.Config
+	if err := yaml.Unmarshal(content, &validConfig); err != nil {
+		t.Fatalf("failed to unmarshal config: %v", err)
+	}
+
+	senderCurve := ecdh.X25519()
+	senderPrivateKey, err := senderCurve.GenerateKey(cryptorand.Reader)
+	if err != nil {
+		t.Fatalf("failed to generate sender random seed: %v", err)
+	}
+	senderPublicKey := senderPrivateKey.PublicKey()
+	senderPublicKeyBytes := senderPublicKey.Bytes()
+
+	recipientCurve := ecdh.X25519()
+	recipientPrivateKey, err := recipientCurve.GenerateKey(cryptorand.Reader)
+	if err != nil {
+		t.Fatalf("failed to generate recipient random seed: %v", err)
+	}
+	recipientPublicKey := recipientPrivateKey.PublicKey()
+	recipientPublicKeyBytes := recipientPublicKey.Bytes()
+
+	var recipientPublicKeyArray, senderPrivateKeyArray [32]byte
+	copy(recipientPublicKeyArray[:], recipientPublicKeyBytes)
+	copy(senderPrivateKeyArray[:], senderPrivateKey.Bytes())
+
+	senderPublicKeyB64 := base64.StdEncoding.EncodeToString(senderPublicKeyBytes)
+
+	recipientPublicKeyB64 := base64.StdEncoding.EncodeToString(recipientPublicKeyBytes)
+
+	// compute the shared secret using the sender's private key and the recipient's public key
+	var sharedSecret [32]byte
+	box.Precompute(&sharedSecret, &recipientPublicKeyArray, &senderPrivateKeyArray)
+
+	// Derive the symmetric key using HKDF with the shared secret
+	hkdfReader := hkdf.New(sha256.New, sharedSecret[:], nil, []byte(api.SymmetricKey))
+	symmetricKey := make([]byte, 32) // AES-GCM requires 32 bytes
+	if _, err := hkdfReader.Read(symmetricKey); err != nil {
+		t.Fatalf("failed to derive symmetric key: %v", err)
+	}
+
+	// Create AES cipher block
+	block, err := aes.NewCipher(symmetricKey)
+	if err != nil {
+		t.Fatalf("failed to create AES cipher")
+	}
+	// Create GCM instance
+	aesGCM, err := cipher.NewGCM(block)
+	if err != nil {
+		t.Fatalf("failed to create AES-GCM")
+	}
+
+	// Generate a random nonce
+	nonce := make([]byte, aesGCM.NonceSize())
+	_, err = cryptorand.Read(nonce)
+	if err != nil {
+		t.Fatalf("failed to generate nonce")
+	}
+
+	// Encrypt the plaintext
+	ciphertext := aesGCM.Seal(nil, nonce, content, nil)
+
+	// Embed the nonce in the ciphertext
+	fullCiphertext := append(nonce, ciphertext...)
+
+	algo := api.AesGcm256
+	data := base64.StdEncoding.EncodeToString(fullCiphertext)
+
+	// this is a valid spec, we want to be able to change fields
+	// without modifying the original, so we have a utility function after
+	validSpec := api.EncryptedSpec{
+		Algorithm:          &algo,
+		Data:               &data,
+		RecipientPublicKey: &recipientPublicKeyB64,
+		SenderPublicKey:    &senderPublicKeyB64,
+	}
+
+	// copy a spec, changing specific fields
+	copyModifySpec := func(opts ...func(*api.EncryptedSpec)) api.EncryptedSpec {
+		copy := validSpec
+		for _, opt := range opts {
+			opt(&copy)
+		}
+		return copy
+	}
+
+	unusedSeed := make([]byte, ed25519.SeedSize)
+	if _, err := io.ReadFull(cryptorand.Reader, unusedSeed); err != nil {
+		t.Fatalf("failed to generate sender random seed: %v", err)
+	}
+
+	// recipient private key credentials
+	recipientCreds := []string{base64.StdEncoding.EncodeToString(recipientPrivateKey.Bytes())}
+	unusedCreds := []string{base64.StdEncoding.EncodeToString(unusedSeed)}
+
+	tests := []struct {
+		name        string
+		inSpec      api.EncryptedSpec
+		credentials []string
+		config      api.Config
+		err         error
+	}{
+		{"no algorithm", copyModifySpec(func(s *api.EncryptedSpec) { s.Algorithm = nil }), recipientCreds, api.Config{}, errors.New("empty algorithm")},
+		{"no data", copyModifySpec(func(s *api.EncryptedSpec) { s.Data = nil }), recipientCreds, api.Config{}, errors.New("empty data")},
+		{"bad base64 data", copyModifySpec(func(s *api.EncryptedSpec) { data := "abcdef"; s.Data = &data }), recipientCreds, api.Config{}, errors.New("failed to decode encrypted data: illegal base64 data")},
+		{"short encrypted data", copyModifySpec(func(s *api.EncryptedSpec) {
+			data := base64.StdEncoding.EncodeToString([]byte("abcdef"))
+			s.Data = &data
+		}), recipientCreds, api.Config{}, errors.New("invalid encrypted data length")},
+		{"invalid encrypted data", copyModifySpec(func(s *api.EncryptedSpec) {
+			bad := nonce
+			bad = append(bad, 1, 2, 3, 4)
+			data := base64.StdEncoding.EncodeToString(bad)
+			s.Data = &data
+		}), recipientCreds, api.Config{}, errors.New("failed to decrypt data: cipher: message authentication failed")},
+		{"empty credentials", validSpec, nil, api.Config{}, errors.New("no private key found that matches public key")},
+		{"unmatched credentials", validSpec, unusedCreds, api.Config{}, errors.New("no private key found that matches public key")},
+		{"success with just one credential", validSpec, recipientCreds, validConfig, nil},
+		{"success with multiple credentials", validSpec, append(recipientCreds, unusedCreds...), validConfig, nil},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			conf, err := decryptConfig(tt.inSpec, tt.credentials)
+			switch {
+			case err == nil && tt.err != nil:
+				t.Fatalf("expected error: %v", tt.err)
+			case err != nil && tt.err == nil:
+				t.Fatalf("unexpected error: %v", err)
+			case err != nil && tt.err != nil && !strings.HasPrefix(err.Error(), tt.err.Error()):
+				t.Fatalf("mismatched error: %v", err)
+			}
+			diff := cmp.Diff(tt.config, conf)
+			if diff != "" {
+				t.Fatalf("mismatched config: %s", diff)
+			}
+		})
+	}
+}

Original file line number	Diff line number	Diff line change
`@@ -31,7 +31,7 @@ require (`
`31`	`31`	`)`
`32`	`32`
`33`	`33`	`require (`
`34`		`- github.com/databacker/api/go/api v0.0.0-20241128084006-ed33dc044eaa`
	`34`	`+ github.com/databacker/api/go/api v0.0.0-20241202154620-01b0380f21cb`
`35`	`35`	`github.com/google/go-cmp v0.6.0`
`36`	`36`	`go.opentelemetry.io/otel v1.31.0`
`37`	`37`	`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp v1.19.0`