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fix object rebinding SSE-C security guarantee violation (#6121)

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This commit fixes a weakness of the key-encryption-key
derivation for SSE-C encrypted objects. Before this
change the key-encryption-key was not bound to / didn't
depend on the object path. This allows an attacker to
repalce objects - encrypted with the same
client-key - with each other.

This change fixes this issue by updating the
key-encryption-key derivation to include:
 - the domain (in this case SSE-C)
 - a canonical object path representation
 - the encryption & key derivation algorithm

Changing the object path now causes the KDF to derive a
different key-encryption-key such that the object-key
unsealing fails.
Including the domain (SSE-C) and encryption & key
derivation algorithm is not directly neccessary for this
fix. However, both will be included for the SSE-S3 KDF.
So they are included here to avoid updating the KDF
again when we add SSE-S3.

The leagcy KDF 'DARE-SHA256' is only used for existing
objects and never for new objects / key rotation.
This commit is contained in:
Andreas Auernhammer
2018-07-10 02:18:28 +02:00
committed by kannappanr
parent 4ddc222f46
commit b181a693fb
5 changed files with 178 additions and 96 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
cmd/encryption-v1_test.go
View File

@@ -308,7 +308,7 @@ func TestEncryptRequest(t *testing.T) {
for k, v := range test.header {
req.Header.Set(k, v)
}
_, err := EncryptRequest(content, req, test.metadata)
_, err := EncryptRequest(content, req, "bucket", "object", test.metadata)
if err != nil {
t.Fatalf("Test %d: Failed to encrypt request: %v", i, err)
}
@@ -328,11 +328,14 @@ func TestEncryptRequest(t *testing.T) {
}
var decryptRequestTests = []struct {
header map[string]string
metadata map[string]string
shouldFail bool
bucket, object string
header map[string]string
metadata map[string]string
shouldFail bool
}{
{
bucket: "bucket",
object: "object",
header: map[string]string{
SSECustomerAlgorithm: "AES256",
SSECustomerKey: "MzJieXRlc2xvbmdzZWNyZXRrZXltdXN0cHJvdmlkZWQ=",
@@ -346,6 +349,23 @@ var decryptRequestTests = []struct {
shouldFail: false,
},
{
bucket: "bucket",
object: "object",
header: map[string]string{
SSECustomerAlgorithm: "AES256",
SSECustomerKey: "MzJieXRlc2xvbmdzZWNyZXRrZXltdXN0cHJvdmlkZWQ=",
SSECustomerKeyMD5: "7PpPLAK26ONlVUGOWlusfg==",
},
metadata: map[string]string{
ServerSideEncryptionSealAlgorithm: SSESealAlgorithmDareV2HmacSha256,
ServerSideEncryptionIV: "qEqmsONcorqlcZXJxaw32H04eyXyXwUgjHzlhkaIYrU=",
ServerSideEncryptionSealedKey: "IAAfAIM14ugTGcM/dIrn4iQMrkl1sjKyeBQ8FBEvRebYj8vWvxG+0cJRpC6NXRU1wJN50JaUOATjO7kz0wZ2mA==",
},
shouldFail: false,
},
{
bucket: "bucket",
object: "object",
header: map[string]string{
SSECustomerAlgorithm: "AES256",
SSECustomerKey: "XAm0dRrJsEsyPb1UuFNezv1bl9hxuYsgUVC/MUctE2k=",
@@ -359,6 +379,8 @@ var decryptRequestTests = []struct {
shouldFail: true,
},
{
bucket: "bucket",
object: "object",
header: map[string]string{
SSECustomerAlgorithm: "AES256",
SSECustomerKey: "XAm0dRrJsEsyPb1UuFNezv1bl9hxuYsgUVC/MUctE2k=",
@@ -372,6 +394,8 @@ var decryptRequestTests = []struct {
shouldFail: true,
},
{
bucket: "bucket",
object: "object",
header: map[string]string{
SSECustomerAlgorithm: "AES256",
SSECustomerKey: "XAm0dRrJsEsyPb1UuFNezv1bl9hxuYsgUVC/MUctE2k=",
@@ -384,21 +408,39 @@ var decryptRequestTests = []struct {
},
shouldFail: true,
},
{
bucket: "bucket",
object: "object-2",
header: map[string]string{
SSECustomerAlgorithm: "AES256",
SSECustomerKey: "MzJieXRlc2xvbmdzZWNyZXRrZXltdXN0cHJvdmlkZWQ=",
SSECustomerKeyMD5: "7PpPLAK26ONlVUGOWlusfg==",
},
metadata: map[string]string{
ServerSideEncryptionSealAlgorithm: SSESealAlgorithmDareV2HmacSha256,
ServerSideEncryptionIV: "qEqmsONcorqlcZXJxaw32H04eyXyXwUgjHzlhkaIYrU=",
ServerSideEncryptionSealedKey: "IAAfAIM14ugTGcM/dIrn4iQMrkl1sjKyeBQ8FBEvRebYj8vWvxG+0cJRpC6NXRU1wJN50JaUOATjO7kz0wZ2mA==",
},
shouldFail: true,
},
}
func TestDecryptRequest(t *testing.T) {
defer func(flag bool) { globalIsSSL = flag }(globalIsSSL)
globalIsSSL = true
for i, test := range decryptRequestTests {
for i, test := range decryptRequestTests[1:] {
client := bytes.NewBuffer(nil)
req := &http.Request{Header: http.Header{}}
for k, v := range test.header {
req.Header.Set(k, v)
}
_, err := DecryptRequest(client, req, test.metadata)
_, err := DecryptRequest(client, req, test.bucket, test.object, test.metadata)
if err != nil && !test.shouldFail {
t.Fatalf("Test %d: Failed to encrypt request: %v", i, err)
}
if err == nil && test.shouldFail {
t.Fatalf("Test %d: should fail but passed", i)
}
if key, ok := test.metadata[SSECustomerKey]; ok {
t.Errorf("Test %d: Client provided key survived in metadata - key: %s", i, key)
}