Add decode support for files with SHA-512 MACs

Fixes: #59

Co-authored-by: charalampos.kailantzis <[email protected]>

mac.go

@@ -9,6 +9,7 @@ import (
 	"crypto/hmac"
 	"crypto/sha1"
 	"crypto/sha256"
+	"crypto/sha512"
 	"crypto/x509/pkix"
 	"encoding/asn1"
 	"hash"
@@ -29,6 +30,7 @@ type digestInfo struct {
 var (
 	oidSHA1   = asn1.ObjectIdentifier([]int{1, 3, 14, 3, 2, 26})
 	oidSHA256 = asn1.ObjectIdentifier([]int{2, 16, 840, 1, 101, 3, 4, 2, 1})
+	oidSHA512 = asn1.ObjectIdentifier([]int{2, 16, 840, 1, 101, 3, 4, 2, 3})
 )
 
 func doMac(macData *macData, message, password []byte) ([]byte, error) {
@@ -41,6 +43,9 @@ func doMac(macData *macData, message, password []byte) ([]byte, error) {
 	case macData.Mac.Algorithm.Algorithm.Equal(oidSHA256):
 		hFn = sha256.New
 		key = pbkdf(sha256Sum, 32, 64, macData.MacSalt, password, macData.Iterations, 3, 32)
+	case macData.Mac.Algorithm.Algorithm.Equal(oidSHA512):
+		hFn = sha512.New
+		key = pbkdf(sha512Sum, 64, 128, macData.MacSalt, password, macData.Iterations, 3, 64)
 	default:
 		return nil, NotImplementedError("unknown digest algorithm: " + macData.Mac.Algorithm.Algorithm.String())
 	}

pbkdf.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"crypto/sha1"
 	"crypto/sha256"
+	"crypto/sha512"
 	"math/big"
 )
 
@@ -27,6 +28,12 @@ func sha256Sum(in []byte) []byte {
 	return sum[:]
 }
 
+// sha512Sum returns the SHA-512 hash of in.
+func sha512Sum(in []byte) []byte {
+	sum := sha512.Sum512(in)
+	return sum[:]
+}
+
 // fillWithRepeats returns v*ceiling(len(pattern) / v) bytes consisting of
 // repeats of pattern.
 func fillWithRepeats(pattern []byte, v int) []byte {