feat: add gpg integration

This commit adds gpg system integration. This is done through two new
packages: gpgbin, which handles the system calls and parsing; and gpg
which is mostly a copy of emersion/go-pgpmail with modifications to
interface with package gpgbin. gpg includes tests for many cases, and
by it's nature also tests package gpgbin. I separated these in case an
external dependency is ever used for the gpg sys-calls/parsing (IE we
mirror how go-pgpmail+openpgp currently are dependencies)

Two new config options are introduced:
* pgp-provider. If it is not explicitly set to "gpg", aerc will default to
it's internal pgp provider
* pgp-key-id: (Optionally) specify a key by short or long keyId

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 62 insertions, 0 deletions

diff --git a/lib/crypto/gpg/gpg.go b/lib/crypto/gpg/gpg.go
new file mode 100644
index 00000000..66cd3725
--- /dev/null
+++ b/lib/crypto/gpg/gpg.go
@@ -0,0 +1,62 @@
+package gpg
+
+import (
+	"bytes"
+	"io"
+	"log"
+	"os/exec"
+
+	"git.sr.ht/~rjarry/aerc/lib/crypto/gpg/gpgbin"
+	"git.sr.ht/~rjarry/aerc/models"
+	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/emersion/go-message/mail"
+)
+
+// Mail satisfies the PGPProvider interface in aerc
+type Mail struct {
+	logger *log.Logger
+}
+
+func (m *Mail) Init(l *log.Logger) error {
+	m.logger = l
+	_, err := exec.LookPath("gpg")
+	return err
+}
+
+func (m *Mail) Decrypt(r io.Reader, decryptKeys openpgp.PromptFunction) (*models.MessageDetails, error) {
+	gpgReader, err := Read(r)
+	if err != nil {
+		return nil, err
+	}
+	md := gpgReader.MessageDetails
+	md.SignatureValidity = models.Valid
+	if md.SignatureError != "" {
+		md.SignatureValidity = handleSignatureError(md.SignatureError)
+	}
+	return md, nil
+}
+
+func (m *Mail) ImportKeys(r io.Reader) error {
+	return gpgbin.Import(r)
+}
+
+func (m *Mail) Encrypt(buf *bytes.Buffer, rcpts []string, signer string, decryptKeys openpgp.PromptFunction, header *mail.Header) (io.WriteCloser, error) {
+
+	return Encrypt(buf, header.Header.Header, rcpts, signer)
+}
+
+func (m *Mail) Sign(buf *bytes.Buffer, signer string, decryptKeys openpgp.PromptFunction, header *mail.Header) (io.WriteCloser, error) {
+	return Sign(buf, header.Header.Header, signer)
+}
+
+func (m *Mail) Close() {}
+
+func handleSignatureError(e string) models.SignatureValidity {
+	if e == "gpg: missing public key" {
+		return models.UnknownEntity
+	}
+	if e == "gpg: header hash does not match actual sig hash" {
+		return models.MicalgMismatch
+	}
+	return models.UnknownValidity
+}