jwe: remove odd doubling/halving

The aescbc implementation already reports an appropriate key size to take the HMAC into account. This doubling can, in some cases, cause a 64-byte AES cipher to be requested. Remove it. This allows jose interop to work in the previously commented out case. Add some more in as well to cover some of the options.
hesusruiz · Dec 15, 2020 · a1e4993 · a1e4993
1 parent c305fbf
commit a1e4993
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Showing 4 changed files with 12 additions and 23 deletions.
diff --git a/jwe/internal/content_crypt/content_crypt.go b/jwe/internal/content_crypt/content_crypt.go
@@ -48,16 +48,10 @@ func NewGeneric(alg jwa.ContentEncryptionAlgorithm) (*Generic, error) {
 		pdebug.Printf("AES Crypt: cipher.keysize = %d", c.KeySize())
 	}
 
-	keysize := c.KeySize()
-	switch alg {
-	case jwa.A128GCM, jwa.A192GCM, jwa.A256GCM:
-	case jwa.A128CBC_HS256, jwa.A192CBC_HS384, jwa.A256CBC_HS512:
-		keysize = keysize * 2
-	}
 	return &Generic{
 		alg:     alg,
 		cipher:  c,
-		keysize: keysize,
+		keysize: c.KeySize(),
 		tagsize: 16,
 	}, nil
 }

diff --git a/jwe/jwe.go b/jwe/jwe.go
@@ -45,7 +45,7 @@ func Encrypt(payload []byte, keyalg jwa.KeyEncryptionAlgorithm, key interface{},
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to create RSA PKCS encrypter")
 		}
-		keysize = contentcrypt.KeySize() / 2
+		keysize = contentcrypt.KeySize()
 	case jwa.RSA_OAEP, jwa.RSA_OAEP_256:
 		var pubkey rsa.PublicKey
 		if err := keyconv.RSAPublicKey(&pubkey, key); err != nil {
@@ -56,7 +56,7 @@ func Encrypt(payload []byte, keyalg jwa.KeyEncryptionAlgorithm, key interface{},
 		if err != nil {
 			return nil, errors.Wrap(err, "failed to create RSA OAEP encrypter")
 		}
-		keysize = contentcrypt.KeySize() / 2
+		keysize = contentcrypt.KeySize()
 	case jwa.A128KW, jwa.A192KW, jwa.A256KW,
 		jwa.A128GCMKW, jwa.A192GCMKW, jwa.A256GCMKW,
 		jwa.PBES2_HS256_A128KW, jwa.PBES2_HS384_A192KW, jwa.PBES2_HS512_A256KW:

diff --git a/jwe/jwe_test.go b/jwe/jwe_test.go
@@ -416,18 +416,6 @@ func TestEncode_ECDH(t *testing.T) {
 	}
 }
 
-func Test_A256KW_A256CBC_HS512(t *testing.T) {
-	var keysize = 32
-	var key = make([]byte, keysize)
-	for i := 0; i < keysize; i++ {
-		key[i] = byte(i)
-	}
-	_, err := jwe.Encrypt([]byte(examplePayload), jwa.A256KW, key, jwa.A256CBC_HS512, jwa.NoCompress)
-	if !assert.Error(t, err, "should fail to encrypt payload") {
-		return
-	}
-}
-
 func Test_GHIssue207(t *testing.T) {
 	// XXX for ECDH-ES
 	// Remove the t.SkipNow()

diff --git a/jwx_test.go b/jwx_test.go
@@ -160,9 +160,16 @@ func TestJoseCompatibility(t *testing.T) {
 	})
 	t.Run("jwe", func(t *testing.T) {
 		tests := []interopTest{
-			// interopTest{jwa.RSA_OAEP, jwa.A128GCM},
+			{jwa.RSA1_5, jwa.A128GCM},
+			{jwa.RSA1_5, jwa.A128CBC_HS256},
+			{jwa.RSA1_5, jwa.A256CBC_HS512},
+			{jwa.RSA_OAEP, jwa.A128GCM},
 			{jwa.RSA_OAEP, jwa.A128CBC_HS256},
-			// interopTest{jwa.ECDH_ES, jwa.A256CBC_HS512},
+			{jwa.RSA_OAEP, jwa.A256CBC_HS512},
+			{jwa.RSA_OAEP_256, jwa.A128GCM},
+			{jwa.RSA_OAEP_256, jwa.A128CBC_HS256},
+			{jwa.RSA_OAEP_256, jwa.A256CBC_HS512},
+			// {jwa.ECDH_ES, jwa.A256CBC_HS512},
 			{jwa.ECDH_ES_A128KW, jwa.A128GCM},
 			{jwa.A256GCMKW, jwa.A256GCM},
 			{jwa.PBES2_HS512_A256KW, jwa.A256GCM},