1 files changed, 177 insertions, 0 deletions
diff --git a/vendor/go.mozilla.org/pkcs7/decrypt.go b/vendor/go.mozilla.org/pkcs7/decrypt.go
new file mode 100644
index 000000000..0d088d628
--- /dev/null
+++ b/vendor/go.mozilla.org/pkcs7/decrypt.go
@@ -0,0 +1,177 @@
+package pkcs7
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/des"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+)
+
+// ErrUnsupportedAlgorithm tells you when our quick dev assumptions have failed
+var ErrUnsupportedAlgorithm = errors.New("pkcs7: cannot decrypt data: only RSA, DES, DES-EDE3, AES-256-CBC and AES-128-GCM supported")
+
+// ErrNotEncryptedContent is returned when attempting to Decrypt data that is not encrypted data
+var ErrNotEncryptedContent = errors.New("pkcs7: content data is a decryptable data type")
+
+// Decrypt decrypts encrypted content info for recipient cert and private key
+func (p7 *PKCS7) Decrypt(cert *x509.Certificate, pkey crypto.PrivateKey) ([]byte, error) {
+	data, ok := p7.raw.(envelopedData)
+	if !ok {
+		return nil, ErrNotEncryptedContent
+	}
+	recipient := selectRecipientForCertificate(data.RecipientInfos, cert)
+	if recipient.EncryptedKey == nil {
+		return nil, errors.New("pkcs7: no enveloped recipient for provided certificate")
+	}
+	switch pkey := pkey.(type) {
+	case *rsa.PrivateKey:
+		var contentKey []byte
+		contentKey, err := rsa.DecryptPKCS1v15(rand.Reader, pkey, recipient.EncryptedKey)
+		if err != nil {
+			return nil, err
+		}
+		return data.EncryptedContentInfo.decrypt(contentKey)
+	}
+	return nil, ErrUnsupportedAlgorithm
+}
+
+// DecryptUsingPSK decrypts encrypted data using caller provided
+// pre-shared secret
+func (p7 *PKCS7) DecryptUsingPSK(key []byte) ([]byte, error) {
+	data, ok := p7.raw.(encryptedData)
+	if !ok {
+		return nil, ErrNotEncryptedContent
+	}
+	return data.EncryptedContentInfo.decrypt(key)
+}
+
+func (eci encryptedContentInfo) decrypt(key []byte) ([]byte, error) {
+	alg := eci.ContentEncryptionAlgorithm.Algorithm
+	if !alg.Equal(OIDEncryptionAlgorithmDESCBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmDESEDE3CBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES256CBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES128CBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES128GCM) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES256GCM) {
+		fmt.Printf("Unsupported Content Encryption Algorithm: %s\n", alg)
+		return nil, ErrUnsupportedAlgorithm
+	}
+
+	// EncryptedContent can either be constructed of multple OCTET STRINGs
+	// or _be_ a tagged OCTET STRING
+	var cyphertext []byte
+	if eci.EncryptedContent.IsCompound {
+		// Complex case to concat all of the children OCTET STRINGs
+		var buf bytes.Buffer
+		cypherbytes := eci.EncryptedContent.Bytes
+		for {
+			var part []byte
+			cypherbytes, _ = asn1.Unmarshal(cypherbytes, &part)
+			buf.Write(part)
+			if cypherbytes == nil {
+				break
+			}
+		}
+		cyphertext = buf.Bytes()
+	} else {
+		// Simple case, the bytes _are_ the cyphertext
+		cyphertext = eci.EncryptedContent.Bytes
+	}
+
+	var block cipher.Block
+	var err error
+
+	switch {
+	case alg.Equal(OIDEncryptionAlgorithmDESCBC):
+		block, err = des.NewCipher(key)
+	case alg.Equal(OIDEncryptionAlgorithmDESEDE3CBC):
+		block, err = des.NewTripleDESCipher(key)
+	case alg.Equal(OIDEncryptionAlgorithmAES256CBC), alg.Equal(OIDEncryptionAlgorithmAES256GCM):
+		fallthrough
+	case alg.Equal(OIDEncryptionAlgorithmAES128GCM), alg.Equal(OIDEncryptionAlgorithmAES128CBC):
+		block, err = aes.NewCipher(key)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	if alg.Equal(OIDEncryptionAlgorithmAES128GCM) || alg.Equal(OIDEncryptionAlgorithmAES256GCM) {
+		params := aesGCMParameters{}
+		paramBytes := eci.ContentEncryptionAlgorithm.Parameters.Bytes
+
+		_, err := asn1.Unmarshal(paramBytes, &params)
+		if err != nil {
+			return nil, err
+		}
+
+		gcm, err := cipher.NewGCM(block)
+		if err != nil {
+			return nil, err
+		}
+
+		if len(params.Nonce) != gcm.NonceSize() {
+			return nil, errors.New("pkcs7: encryption algorithm parameters are incorrect")
+		}
+		if params.ICVLen != gcm.Overhead() {
+			return nil, errors.New("pkcs7: encryption algorithm parameters are incorrect")
+		}
+
+		plaintext, err := gcm.Open(nil, params.Nonce, cyphertext, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		return plaintext, nil
+	}
+
+	iv := eci.ContentEncryptionAlgorithm.Parameters.Bytes
+	if len(iv) != block.BlockSize() {
+		return nil, errors.New("pkcs7: encryption algorithm parameters are malformed")
+	}
+	mode := cipher.NewCBCDecrypter(block, iv)
+	plaintext := make([]byte, len(cyphertext))
+	mode.CryptBlocks(plaintext, cyphertext)
+	if plaintext, err = unpad(plaintext, mode.BlockSize()); err != nil {
+		return nil, err
+	}
+	return plaintext, nil
+}
+
+func unpad(data []byte, blocklen int) ([]byte, error) {
+	if blocklen < 1 {
+		return nil, fmt.Errorf("invalid blocklen %d", blocklen)
+	}
+	if len(data)%blocklen != 0 || len(data) == 0 {
+		return nil, fmt.Errorf("invalid data len %d", len(data))
+	}
+
+	// the last byte is the length of padding
+	padlen := int(data[len(data)-1])
+
+	// check padding integrity, all bytes should be the same
+	pad := data[len(data)-padlen:]
+	for _, padbyte := range pad {
+		if padbyte != byte(padlen) {
+			return nil, errors.New("invalid padding")
+		}
+	}
+
+	return data[:len(data)-padlen], nil
+}
+
+func selectRecipientForCertificate(recipients []recipientInfo, cert *x509.Certificate) recipientInfo {
+	for _, recp := range recipients {
+		if isCertMatchForIssuerAndSerial(cert, recp.IssuerAndSerialNumber) {
+			return recp
+		}
+	}
+	return recipientInfo{}
+}