Updated keyScan to ignore trailing spaces in KEYINFO attributes

agent/conn.go

@@ -115,7 +115,14 @@ func (conn *Conn) Close() error {
 }
 
 func keyScan(key *Key, line string) error {
-	parts := strings.Split(line, " ")
+	unfilteredParts := strings.Split(line, " ")
+	parts := []string{}
+	for _, p := range unfilteredParts {
+		if p != "" {
+			parts = append(parts, p)
+		}
+	}
+
 	if len(parts) != 10 {
 		return fmt.Errorf("illegal format for KEYINFO line")
 	}
@@ -226,6 +233,60 @@ func (conn *Conn) Keys() ([]Key, error) {
 	return keyList, nil
 }
 
+// KeyGrips returns a list of available keygrips, indexed by CardID, by querying the card
+func (conn *Conn) KeyGrips() (map[string]string, error) {
+	grips := map[string]string{}
+
+	scan := func(key *Key, line string) error {
+		unfilteredParts := strings.Split(line, " ")
+		var parts []string
+		for _, p := range unfilteredParts {
+			if p != "" {
+				parts = append(parts, p)
+			}
+		}
+
+		if len(parts) < 3 {
+			return fmt.Errorf("illegal format for KEYINFO line: %s", line)
+		}
+
+		keygrip := parts[1]
+		cardID := parts[2]
+		if strings.HasPrefix(cardID, "OPENPGP.") &&  len(keygrip) == 40 {
+			// grips[cardID] = keygrip
+			grips[cardID] = keygrip
+		} else {
+			fmt.Printf("Warning: card ID or keygrip invalid, skipping: %s", line)
+		}
+
+
+		return nil
+	}
+
+	respFunc := func(respType, data string) error {
+		if respType != "S" || !strings.HasPrefix(data, "KEYPAIRINFO ") {
+			return nil
+		}
+
+		var key Key
+		if err := scan(&key, data); err != nil {
+			return err
+		}
+
+		return nil
+	}
+
+	conn.mu.Lock()
+	defer conn.mu.Unlock()
+
+	err := conn.Raw(respFunc, "scd LEARN --force")
+	if err != nil {
+		return nil, err
+	}
+
+	return grips, nil
+}
+
 // Raw executes a command and pipes its results to the specified ResponseFunc
 // parameter.
 func (conn *Conn) Raw(f ResponseFunc, format string, a ...interface{}) error {

agent/key.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"bytes"
 	"crypto"
 	"crypto/rsa"
 	"encoding/hex"
@@ -119,8 +120,22 @@ func (key Key) Sign(rand io.Reader, msg []byte, opts crypto.SignerOpts) (signatu
 			return internalrsa.SignPSS(rand, priv, pssOpts.Hash, msg, pssOpts)
 		}
 
-		return key.signPKCS1v15(msg, opts.HashFunc())
+		sig, err := key.signPKCS1v15(msg, opts.HashFunc())
+		if err != nil {
+			return nil, err
+		}
+
+		if diff := len(sig) - pub.Size(); diff > 0 {
+			// It seems sometimes the signature can have leading zero bytes such that its over the keysize
+			leadingZeros := bytes.Repeat([]byte{00}, diff)
+			if !bytes.HasPrefix(sig, leadingZeros) {
+				return nil, errors.New("github.com/prep/gpg/agent: signature length too large with nonzero leading bytes")
+			}
+			// We trim the leading zeros
+			sig = bytes.TrimPrefix(sig, leadingZeros)
+		}
 
+		return sig, nil
 	default:
 		return nil, errors.New("github.com/prep/gpg/agent: unknown public key")
 	}