Adding PGP decrypt to auth package

Adding PGP decrypt function to auth.
This can be used by quorum client in its code for decryption

Issue-ID: AAF-165
Change-Id: I6d236c3164ccb93c11527ac8c2e725987236f9f0
Signed-off-by: Kiran Kamineni <kiran.k.kamineni@intel.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/sms-service/src/sms/auth/auth.go b/sms-service/src/sms/auth/auth.go
index 341f377..ad5afdc 100644
--- a/sms-service/src/sms/auth/auth.go
+++ b/sms-service/src/sms/auth/auth.go
@@ -22,6 +22,7 @@ import (
 	"crypto/x509"
 	"encoding/base64"
 	"golang.org/x/crypto/openpgp"
+	"golang.org/x/crypto/openpgp/packet"
 	"io/ioutil"
 
 	smslogger "sms/log"
@@ -93,3 +94,38 @@ func GeneratePGPKeyPair() (string, string, error) {
 
 	return pbkey, prkey, nil
 }
+
+// DecryptPGPBytes decrypts a PGP encoded input string and returns
+// a base64 representation of the decoded string
+func DecryptPGPBytes(data string, prKey string) (string, error) {
+	// Convert private key to bytes from base64
+	prKeyBytes, err := base64.StdEncoding.DecodeString(prKey)
+	if err != nil {
+		smslogger.WriteError("Error Decoding base64 private key: " + err.Error())
+		return "", err
+	}
+
+	dataBytes, err := base64.StdEncoding.DecodeString(data)
+	if err != nil {
+		smslogger.WriteError("Error Decoding base64 data: " + err.Error())
+		return "", err
+	}
+
+	prEntity, err := openpgp.ReadEntity(packet.NewReader(bytes.NewBuffer(prKeyBytes)))
+	if err != nil {
+		smslogger.WriteError("Error reading entity from PGP key: " + err.Error())
+		return "", err
+	}
+
+	prEntityList := &openpgp.EntityList{prEntity}
+	message, err := openpgp.ReadMessage(bytes.NewBuffer(dataBytes), prEntityList, nil, nil)
+	if err != nil {
+		smslogger.WriteError("Error Decrypting message: " + err.Error())
+		return "", err
+	}
+
+	var retBuf bytes.Buffer
+	retBuf.ReadFrom(message.UnverifiedBody)
+
+	return retBuf.String(), nil
+}