Merge pull request #2 from oeufdure/master

Various fixes

ber.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 )
 
-var encodeIndent = 0
+// var encodeIndent = 0
 
 type asn1Object interface {
 	EncodeTo(writer *bytes.Buffer) error
@@ -18,15 +18,15 @@ type asn1Structured struct {
 
 func (s asn1Structured) EncodeTo(out *bytes.Buffer) error {
 	//fmt.Printf("%s--> tag: % X\n", strings.Repeat("| ", encodeIndent), s.tagBytes)
-	encodeIndent++
+	//encodeIndent++
 	inner := new(bytes.Buffer)
 	for _, obj := range s.content {
 		err := obj.EncodeTo(inner)
 		if err != nil {
 			return err
 		}
 	}
-	encodeIndent--
+	//encodeIndent--
 	out.Write(s.tagBytes)
 	encodeLength(out, inner.Len())
 	out.Write(inner.Bytes())
@@ -133,49 +133,35 @@ func encodeLength(out *bytes.Buffer, length int) (err error) {
 }
 
 func readObject(ber []byte, offset int) (asn1Object, int, error) {
-	berLen := len(ber)
-	if offset >= berLen {
-		return nil, 0, errors.New("ber2der: offset is after end of ber data")
-	}
+	//fmt.Printf("\n====> Starting readObject at offset: %d\n\n", offset)
 	tagStart := offset
 	b := ber[offset]
 	offset++
-	if offset >= berLen {
-		return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
-	}
 	tag := b & 0x1F // last 5 bits
 	if tag == 0x1F {
 		tag = 0
 		for ber[offset] >= 0x80 {
 			tag = tag*128 + ber[offset] - 0x80
 			offset++
-			if offset > berLen {
-				return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
-			}
 		}
-		// jvehent 20170227: this doesn't appear to be used anywhere...
-		//tag = tag*128 + ber[offset] - 0x80
+		tag = tag*128 + ber[offset] - 0x80
 		offset++
-		if offset > berLen {
-			return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
-		}
 	}
 	tagEnd := offset
 
 	kind := b & 0x20
-	if kind == 0 {
-		debugprint("--> Primitive\n")
-	} else {
-		debugprint("--> Constructed\n")
-	}
+	/*
+		if kind == 0 {
+			fmt.Print("--> Primitive\n")
+		} else {
+			fmt.Print("--> Constructed\n")
+		}
+	*/
 	// read length
 	var length int
 	l := ber[offset]
 	offset++
-	if offset > berLen {
-		return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
-	}
-	hack := 0
+	indefinite := false
 	if l > 0x80 {
 		numberOfBytes := (int)(l & 0x7F)
 		if numberOfBytes > 4 { // int is only guaranteed to be 32bit
@@ -184,42 +170,33 @@ func readObject(ber []byte, offset int) (asn1Object, int, error) {
 		if numberOfBytes == 4 && (int)(ber[offset]) > 0x7F {
 			return nil, 0, errors.New("ber2der: BER tag length is negative")
 		}
-		if (int)(ber[offset]) == 0x0 {
+		if 0x0 == (int)(ber[offset]) {
 			return nil, 0, errors.New("ber2der: BER tag length has leading zero")
 		}
-		debugprint("--> (compute length) indicator byte: %x\n", l)
-		debugprint("--> (compute length) length bytes: % X\n", ber[offset:offset+numberOfBytes])
+		//fmt.Printf("--> (compute length) indicator byte: %x\n", l)
+		//fmt.Printf("--> (compute length) length bytes: % X\n", ber[offset:offset+numberOfBytes])
 		for i := 0; i < numberOfBytes; i++ {
 			length = length*256 + (int)(ber[offset])
 			offset++
-			if offset > berLen {
-				return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
-			}
 		}
 	} else if l == 0x80 {
-		// find length by searching content
-		markerIndex := bytes.LastIndex(ber[offset:], []byte{0x0, 0x0})
-		if markerIndex == -1 {
-			return nil, 0, errors.New("ber2der: Invalid BER format")
-		}
-		length = markerIndex
-		hack = 2
-		debugprint("--> (compute length) marker found at offset: %d\n", markerIndex+offset)
+		indefinite = true
 	} else {
 		length = (int)(l)
 	}
-	if length < 0 {
-		return nil, 0, errors.New("ber2der: invalid negative value found in BER tag length")
-	}
+
 	//fmt.Printf("--> length        : %d\n", length)
 	contentEnd := offset + length
 	if contentEnd > len(ber) {
 		return nil, 0, errors.New("ber2der: BER tag length is more than available data")
 	}
-	debugprint("--> content start : %d\n", offset)
-	debugprint("--> content end   : %d\n", contentEnd)
-	debugprint("--> content       : % X\n", ber[offset:contentEnd])
+	//fmt.Printf("--> content start : %d\n", offset)
+	//fmt.Printf("--> content end   : %d\n", contentEnd)
+	//fmt.Printf("--> content       : % X\n", ber[offset:contentEnd])
 	var obj asn1Object
+	if indefinite && kind == 0 {
+		return nil, 0, errors.New("ber2der: Indefinite form tag must have constructed encoding")
+	}
 	if kind == 0 {
 		obj = asn1Primitive{
 			tagBytes: ber[tagStart:tagEnd],
@@ -228,24 +205,44 @@ func readObject(ber []byte, offset int) (asn1Object, int, error) {
 		}
 	} else {
 		var subObjects []asn1Object
-		for offset < contentEnd {
+		for (offset < contentEnd) || indefinite {
 			var subObj asn1Object
 			var err error
-			subObj, offset, err = readObject(ber[:contentEnd], offset)
+			subObj, offset, err = readObject(ber, offset)
 			if err != nil {
 				return nil, 0, err
 			}
 			subObjects = append(subObjects, subObj)
+
+			if indefinite {
+				terminated, err := isIndefiniteTermination(ber, offset)
+				if err != nil {
+					return nil, 0, err
+				}
+
+				if terminated {
+					break
+				}
+			}
 		}
 		obj = asn1Structured{
 			tagBytes: ber[tagStart:tagEnd],
 			content:  subObjects,
 		}
 	}
 
-	return obj, contentEnd + hack, nil
+	// Apply indefinite form length with 0x0000 terminator.
+	if indefinite {
+		contentEnd = offset + 2
+	}
+
+	return obj, contentEnd, nil
 }
 
-func debugprint(format string, a ...interface{}) {
-	//fmt.Printf(format, a)
+func isIndefiniteTermination(ber []byte, offset int) (bool, error) {
+	if len(ber) - offset < 2 {
+		return false, errors.New("ber2der: Invalid BER format")
+	}
+
+	return bytes.Index(ber[offset:], []byte{0x0, 0x0}) == 0, nil
 }

ber_test.go

@@ -15,7 +15,7 @@ func TestBer2Der(t *testing.T) {
 	if err != nil {
 		t.Fatalf("ber2der failed with error: %v", err)
 	}
-	if !bytes.Equal(der, expected) {
+	if bytes.Compare(der, expected) != 0 {
 		t.Errorf("ber2der result did not match.\n\tExpected: % X\n\tActual: % X", expected, der)
 	}
 
@@ -42,12 +42,11 @@ func TestBer2Der_Negatives(t *testing.T) {
 		Input         []byte
 		ErrorContains string
 	}{
-		{[]byte{0x30, 0x85}, "tag length too long"},
+		{[]byte{0x30, 0x85}, "length too long"},
 		{[]byte{0x30, 0x84, 0x80, 0x0, 0x0, 0x0}, "length is negative"},
 		{[]byte{0x30, 0x82, 0x0, 0x1}, "length has leading zero"},
-		{[]byte{0x30, 0x80, 0x1, 0x2}, "Invalid BER format"},
+		{[]byte{0x30, 0x80, 0x1, 0x2, 0x1, 0x2}, "Invalid BER format"},
 		{[]byte{0x30, 0x03, 0x01, 0x02}, "length is more than available data"},
-		{[]byte{0x30}, "end of ber data reached"},
 	}
 
 	for _, fixture := range fixtures {
@@ -60,3 +59,39 @@ func TestBer2Der_Negatives(t *testing.T) {
 		}
 	}
 }
+
+func TestBer2Der_NestedMultipleIndefinite(t *testing.T) {
+	// indefinite length fixture
+	ber := []byte{0x30, 0x80, 0x30, 0x80, 0x02, 0x01, 0x01, 0x00, 0x00, 0x30, 0x80, 0x02, 0x01, 0x02, 0x00, 0x00, 0x00, 0x00}
+	expected := []byte{0x30, 0x0A, 0x30, 0x03, 0x02, 0x01, 0x01, 0x30, 0x03, 0x02, 0x01, 0x02}
+
+	der, err := ber2der(ber)
+	if err != nil {
+		t.Fatalf("ber2der failed with error: %v", err)
+	}
+	if bytes.Compare(der, expected) != 0 {
+		t.Errorf("ber2der result did not match.\n\tExpected: % X\n\tActual: % X", expected, der)
+	}
+
+	if der2, err := ber2der(der); err != nil {
+		t.Errorf("ber2der on DER bytes failed with error: %v", err)
+	} else {
+		if !bytes.Equal(der, der2) {
+			t.Error("ber2der is not idempotent")
+		}
+	}
+	var thing struct {
+		Nest1 struct {
+			Number int
+		}
+		Nest2 struct {
+			Number int
+		}
+	}
+	rest, err := asn1.Unmarshal(der, &thing)
+	if err != nil {
+		t.Errorf("Cannot parse resulting DER because: %v", err)
+	} else if len(rest) > 0 {
+		t.Errorf("Resulting DER has trailing data: % X", rest)
+	}
+}

encrypt.go

@@ -60,7 +60,7 @@ const (
 // ContentEncryptionAlgorithm determines the algorithm used to encrypt the
 // plaintext message. Change the value of this variable to change which
 // algorithm is used in the Encrypt() function.
-var ContentEncryptionAlgorithm = EncryptionAlgorithmDESCBC
+var ContentEncryptionAlgorithm = EncryptionAlgorithmAES128CBC
 
 // ErrUnsupportedEncryptionAlgorithm is returned when attempting to encrypt
 // content with an unsupported algorithm.

pkcs7.go

@@ -158,6 +158,7 @@ func Parse(data []byte) (p7 *PKCS7, err error) {
 	}
 	var info contentInfo
 	der, err := ber2der(data)
+
 	if err != nil {
 		return nil, err
 	}

verify.go

@@ -53,6 +53,7 @@ func verifySignature(p7 *PKCS7, signer signerInfo, truststore *x509.CertPool) (e
 		h := hash.New()
 		h.Write(p7.Content)
 		computed := h.Sum(nil)
+
 		if subtle.ConstantTimeCompare(digest, computed) != 1 {
 			return &MessageDigestMismatchError{
 				ExpectedDigest: digest,
@@ -113,36 +114,53 @@ func (p7 *PKCS7) UnmarshalSignedAttribute(attributeType asn1.ObjectIdentifier, o
 func parseSignedData(data []byte) (*PKCS7, error) {
 	var sd signedData
 	asn1.Unmarshal(data, &sd)
+
 	certs, err := sd.Certificates.Parse()
 	if err != nil {
 		return nil, err
 	}
 	// fmt.Printf("--> Signed Data Version %d\n", sd.Version)
 
 	var compound asn1.RawValue
-	var content unsignedData
 
 	// The Content.Bytes maybe empty on PKI responses.
+
+	if rest, err := asn1.Unmarshal(sd.ContentInfo.Content.Bytes, &compound); err != nil {
+		return nil, err
+	} else if len(rest) > 0 {
+		return nil, errors.New("unexpected trailing data")
+	}
+
+	if compound.Class != asn1.ClassUniversal || compound.Tag != asn1.TagOctetString {
+		return nil, errors.New("bad tag or class")
+	}
+
 	if len(sd.ContentInfo.Content.Bytes) > 0 {
 		if _, err := asn1.Unmarshal(sd.ContentInfo.Content.Bytes, &compound); err != nil {
 			return nil, err
 		}
 	}
-	// Compound octet string
+
+	var value []byte
+
 	if compound.IsCompound {
-		if compound.Tag == 4 {
-			if _, err = asn1.Unmarshal(compound.Bytes, &content); err != nil {
+		rest := compound.Bytes
+		for len(rest) > 0 {
+			if rest, err = asn1.Unmarshal(rest, &compound); err != nil {
 				return nil, err
 			}
-		} else {
-			content = compound.Bytes
+			// Don't allow further constructed types.
+			if compound.Class != asn1.ClassUniversal || compound.Tag != asn1.TagOctetString || compound.IsCompound {
+				return nil, errors.New("bad class or tag")
+			}
+			value = append(value, compound.Bytes...)
 		}
 	} else {
-		// assuming this is tag 04
-		content = compound.Bytes
+		value = compound.Bytes
 	}
+
 	return &PKCS7{
-		Content:      content,
+		Content:      value,
 		Certificates: certs,
 		CRLs:         sd.CRLs,
 		Signers:      sd.SignerInfos,
@@ -199,13 +217,19 @@ func getSignatureAlgorithm(digestEncryption, digest pkix.AlgorithmIdentifier) (x
 		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA384),
 		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA512):
 		switch {
-		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1):
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1),
+			// Some Microsoft issued certificates use the general RSA algorithm
+			// for the encrypt OID and the digest+algorithm OID for the digest.
+			digest.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA1):
 			return x509.SHA1WithRSA, nil
-		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA256):
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA256),
+			digest.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA256):
 			return x509.SHA256WithRSA, nil
-		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA384):
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA384),
+			digest.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA384):
 			return x509.SHA384WithRSA, nil
-		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA512):
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA512),
+			digest.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA512):
 			return x509.SHA512WithRSA, nil
 		default:
 			return -1, fmt.Errorf("pkcs7: unsupported digest %q for encryption algorithm %q",
@@ -214,7 +238,8 @@ func getSignatureAlgorithm(digestEncryption, digest pkix.AlgorithmIdentifier) (x
 	case digestEncryption.Algorithm.Equal(OIDDigestAlgorithmDSA),
 		digestEncryption.Algorithm.Equal(OIDDigestAlgorithmDSASHA1):
 		switch {
-		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1):
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1),
+			digest.Algorithm.Equal(OIDDigestAlgorithmDSASHA1):
 			return x509.DSAWithSHA1, nil
 		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA256):
 			return x509.DSAWithSHA256, nil