Merge pull request #119 from ebiggers/adiantum

Add support for the Adiantum encryption mode

3 files changed, 77 insertions, 56 deletions

diff --git a/metadata/metadata.pb.go b/metadata/metadata.pb.go
index 94d5662..2b62a91 100644
--- a/metadata/metadata.pb.go
+++ b/metadata/metadata.pb.go
@@ -45,7 +45,7 @@ func (x SourceType) String() string {
 	return proto.EnumName(SourceType_name, int32(x))
 }
 func (SourceType) EnumDescriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{0}
+	return fileDescriptor_metadata_5e732a616277e389, []int{0}
 }
 
 // Type of encryption; should match declarations of unix.FS_ENCRYPTION_MODE
@@ -59,6 +59,7 @@ const (
 	EncryptionOptions_AES_256_CTS EncryptionOptions_Mode = 4
 	EncryptionOptions_AES_128_CBC EncryptionOptions_Mode = 5
 	EncryptionOptions_AES_128_CTS EncryptionOptions_Mode = 6
+	EncryptionOptions_Adiantum    EncryptionOptions_Mode = 9
 )
 
 var EncryptionOptions_Mode_name = map[int32]string{
@@ -69,6 +70,7 @@ var EncryptionOptions_Mode_name = map[int32]string{
 	4: "AES_256_CTS",
 	5: "AES_128_CBC",
 	6: "AES_128_CTS",
+	9: "Adiantum",
 }
 var EncryptionOptions_Mode_value = map[string]int32{
 	"default":     0,
@@ -78,13 +80,14 @@ var EncryptionOptions_Mode_value = map[string]int32{
 	"AES_256_CTS": 4,
 	"AES_128_CBC": 5,
 	"AES_128_CTS": 6,
+	"Adiantum":    9,
 }
 
 func (x EncryptionOptions_Mode) String() string {
 	return proto.EnumName(EncryptionOptions_Mode_name, int32(x))
 }
 func (EncryptionOptions_Mode) EnumDescriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{3, 0}
+	return fileDescriptor_metadata_5e732a616277e389, []int{3, 0}
 }
 
 // Cost parameters to be used in our hashing functions.
@@ -101,7 +104,7 @@ func (m *HashingCosts) Reset()         { *m = HashingCosts{} }
 func (m *HashingCosts) String() string { return proto.CompactTextString(m) }
 func (*HashingCosts) ProtoMessage()    {}
 func (*HashingCosts) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{0}
+	return fileDescriptor_metadata_5e732a616277e389, []int{0}
 }
 func (m *HashingCosts) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_HashingCosts.Unmarshal(m, b)
@@ -156,7 +159,7 @@ func (m *WrappedKeyData) Reset()         { *m = WrappedKeyData{} }
 func (m *WrappedKeyData) String() string { return proto.CompactTextString(m) }
 func (*WrappedKeyData) ProtoMessage()    {}
 func (*WrappedKeyData) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{1}
+	return fileDescriptor_metadata_5e732a616277e389, []int{1}
 }
 func (m *WrappedKeyData) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_WrappedKeyData.Unmarshal(m, b)
@@ -216,7 +219,7 @@ func (m *ProtectorData) Reset()         { *m = ProtectorData{} }
 func (m *ProtectorData) String() string { return proto.CompactTextString(m) }
 func (*ProtectorData) ProtoMessage()    {}
 func (*ProtectorData) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{2}
+	return fileDescriptor_metadata_5e732a616277e389, []int{2}
 }
 func (m *ProtectorData) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_ProtectorData.Unmarshal(m, b)
@@ -299,7 +302,7 @@ func (m *EncryptionOptions) Reset()         { *m = EncryptionOptions{} }
 func (m *EncryptionOptions) String() string { return proto.CompactTextString(m) }
 func (*EncryptionOptions) ProtoMessage()    {}
 func (*EncryptionOptions) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{3}
+	return fileDescriptor_metadata_5e732a616277e389, []int{3}
 }
 func (m *EncryptionOptions) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_EncryptionOptions.Unmarshal(m, b)
@@ -352,7 +355,7 @@ func (m *WrappedPolicyKey) Reset()         { *m = WrappedPolicyKey{} }
 func (m *WrappedPolicyKey) String() string { return proto.CompactTextString(m) }
 func (*WrappedPolicyKey) ProtoMessage()    {}
 func (*WrappedPolicyKey) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{4}
+	return fileDescriptor_metadata_5e732a616277e389, []int{4}
 }
 func (m *WrappedPolicyKey) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_WrappedPolicyKey.Unmarshal(m, b)
@@ -400,7 +403,7 @@ func (m *PolicyData) Reset()         { *m = PolicyData{} }
 func (m *PolicyData) String() string { return proto.CompactTextString(m) }
 func (*PolicyData) ProtoMessage()    {}
 func (*PolicyData) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{5}
+	return fileDescriptor_metadata_5e732a616277e389, []int{5}
 }
 func (m *PolicyData) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_PolicyData.Unmarshal(m, b)
@@ -456,7 +459,7 @@ func (m *Config) Reset()         { *m = Config{} }
 func (m *Config) String() string { return proto.CompactTextString(m) }
 func (*Config) ProtoMessage()    {}
 func (*Config) Descriptor() ([]byte, []int) {
-	return fileDescriptor_metadata_e565bd6b3feb0969, []int{6}
+	return fileDescriptor_metadata_5e732a616277e389, []int{6}
 }
 func (m *Config) XXX_Unmarshal(b []byte) error {
 	return xxx_messageInfo_Config.Unmarshal(m, b)
@@ -516,49 +519,49 @@ func init() {
 	proto.RegisterEnum("metadata.EncryptionOptions_Mode", EncryptionOptions_Mode_name, EncryptionOptions_Mode_value)
 }
 
-func init() { proto.RegisterFile("metadata/metadata.proto", fileDescriptor_metadata_e565bd6b3feb0969) }
-
-var fileDescriptor_metadata_e565bd6b3feb0969 = []byte{
-	// 641 bytes of a gzipped FileDescriptorProto
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-	0xc0, 0x65, 0xb1, 0x0a, 0xa6, 0x76, 0x7b, 0x30, 0x4f, 0x3f, 0x03, 0x2c, 0x2a, 0x5d, 0x7e, 0x89,
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-	0x00,
+func init() { proto.RegisterFile("metadata/metadata.proto", fileDescriptor_metadata_5e732a616277e389) }
+
+var fileDescriptor_metadata_5e732a616277e389 = []byte{
+	// 656 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x9c, 0x94, 0xef, 0x6a, 0xdb, 0x3c,
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+	0xd3, 0x1e, 0xc0, 0x84, 0xc8, 0xc9, 0x38, 0x6f, 0x20, 0xfb, 0xd6, 0x06, 0x6a, 0xea, 0x95, 0xf9,
+	0x2f, 0xea, 0x21, 0x74, 0x02, 0x1e, 0x0b, 0xa2, 0xd8, 0x39, 0x8b, 0x98, 0xca, 0xe6, 0xfd, 0xb8,
+	0x2c, 0x56, 0xc1, 0xd4, 0xee, 0x0e, 0xe6, 0xf1, 0x07, 0x80, 0x45, 0xa5, 0xcb, 0xef, 0x12, 0x41,
+	0x57, 0x90, 0x78, 0x2c, 0x88, 0x94, 0x62, 0x92, 0x12, 0x49, 0x5d, 0x0b, 0xfd, 0x07, 0x6b, 0xc1,
+	0x54, 0x2a, 0xbe, 0x24, 0xdb, 0x7a, 0x5f, 0x4a, 0x66, 0x9a, 0xa9, 0xeb, 0x9c, 0xd7, 0xcd, 0x3f,
+	0xf7, 0xe9, 0xef, 0x00, 0x00, 0x00, 0xff, 0xff, 0x4b, 0xbe, 0x84, 0xbc, 0x8e, 0x05, 0x00, 0x00,
 }
diff --git a/metadata/metadata.proto b/metadata/metadata.proto
index 5e1b9dd..6fe0ad9 100644
--- a/metadata/metadata.proto
+++ b/metadata/metadata.proto
@@ -72,6 +72,7 @@ message EncryptionOptions {
     AES_256_CTS = 4;
     AES_128_CBC = 5;
     AES_128_CTS = 6;
+    Adiantum = 9;
   }
 
   Mode contents = 2;
diff --git a/metadata/policy.go b/metadata/policy.go
index d83aa9d..7926e9e 100644
--- a/metadata/policy.go
+++ b/metadata/policy.go
@@ -109,6 +109,18 @@ func GetPolicy(path string) (*PolicyData, error) {
 	}, nil
 }
 
+// For improved performance, use the DIRECT_KEY flag when using ciphers that
+// support it, e.g. Adiantum.  It is safe because fscrypt won't reuse the key
+// for any other policy.  (Multiple directories with same policy are okay.)
+func shouldUseDirectKeyFlag(options *EncryptionOptions) bool {
+	// Contents and filenames encryption modes must be the same
+	if options.Contents != options.Filenames {
+		return false
+	}
+	// Whitelist the modes that take a 24+ byte IV (enough room for the per-file nonce)
+	return options.Contents == EncryptionOptions_Adiantum
+}
+
 // SetPolicy sets up the specified directory to be encrypted with the specified
 // policy. Returns an error if we cannot set the policy for any reason (not a
 // directory, invalid options or KeyDescriptor, etc).
@@ -124,7 +136,7 @@ func SetPolicy(path string, data *PolicyData) error {
 	}
 
 	// This lookup should always succeed (as policy is valid)
-	paddingFlag, ok := util.Lookup(data.Options.Padding, paddingArray, flagsArray)
+	flags, ok := util.Lookup(data.Options.Padding, paddingArray, flagsArray)
 	if !ok {
 		log.Panicf("padding of %d was not found", data.Options.Padding)
 	}
@@ -134,11 +146,16 @@ func SetPolicy(path string, data *PolicyData) error {
 		return errors.New("invalid descriptor: " + data.KeyDescriptor)
 	}
 
+	if shouldUseDirectKeyFlag(data.Options) {
+		// TODO: use unix.FS_POLICY_FLAG_DIRECT_KEY here once available
+		flags |= 0x4
+	}
+
 	policy := unix.FscryptPolicy{
 		Version:                   0, // Version must always be zero
 		Contents_encryption_mode:  uint8(data.Options.Contents),
 		Filenames_encryption_mode: uint8(data.Options.Filenames),
-		Flags:                     uint8(paddingFlag),
+		Flags:                     uint8(flags),
 	}
 	copy(policy.Master_key_descriptor[:], descriptorBytes)