pgp: add attach key command

Add compose command ("attach-key") to attach the public key associated
with the sending account. Public key is attached in ascii armor format,
with the mimetype set according to RFC 3156 ("application/pgp-keys").

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Tested-by: Koni Marti <koni.marti@gmail.com>

2 files changed, 26 insertions, 1 deletions

diff --git a/lib/crypto/gpg/gpg.go b/lib/crypto/gpg/gpg.go
index fe32468c..00125ba6 100644
--- a/lib/crypto/gpg/gpg.go
+++ b/lib/crypto/gpg/gpg.go
@@ -59,6 +59,10 @@ func (m *Mail) GetKeyId(s string) (string, error) {
 	return gpgbin.GetKeyId(s)
 }
 
+func (m *Mail) ExportKey(k string) (io.Reader, error) {
+	return gpgbin.ExportPublicKey(k)
+}
+
 func handleSignatureError(e string) models.SignatureValidity {
 	if e == "gpg: missing public key" {
 		return models.UnknownEntity
diff --git a/lib/crypto/gpg/gpgbin/keys.go b/lib/crypto/gpg/gpgbin/keys.go
index 9c8b233f..bef90cf6 100644
--- a/lib/crypto/gpg/gpgbin/keys.go
+++ b/lib/crypto/gpg/gpgbin/keys.go
@@ -1,6 +1,12 @@
 package gpgbin
 
-import "fmt"
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os/exec"
+	"strings"
+)
 
 // GetPrivateKeyId runs gpg --list-secret-keys s
 func GetPrivateKeyId(s string) (string, error) {
@@ -21,3 +27,18 @@ func GetKeyId(s string) (string, error) {
 	}
 	return id, nil
 }
+
+// ExportPublicKey exports the public key identified by k in armor format
+func ExportPublicKey(k string) (io.Reader, error) {
+	cmd := exec.Command("gpg", "--export", "--armor", k)
+
+	var outbuf bytes.Buffer
+	var stderr strings.Builder
+	cmd.Stdout = &outbuf
+	cmd.Stderr = &stderr
+	cmd.Run()
+	if strings.Contains(stderr.String(), "gpg") {
+		return nil, fmt.Errorf("gpg: error exporting key")
+	}
+	return &outbuf, nil
+}