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>

2 files changed, 11 insertions, 1 deletions

diff --git a/config/aerc.conf b/config/aerc.conf
index 00c6c49..1a3c1f4 100644
--- a/config/aerc.conf
+++ b/config/aerc.conf
@@ -3,6 +3,12 @@
 
 [general]
 #
+# If set to "gpg", aerc will use system gpg binary and keystore for all crypto
+# operations. Otherwise, the internal openpgp implemenation will be used.
+#
+# Default: internal
+pgp-provider=internal
+
 # By default, the file permissions of accounts.conf must be restrictive and
 # only allow reading by the file owner (0600). Set this option to true to
 # ignore this permission check. Use this with care as it may expose your
diff --git a/config/config.go b/config/config.go
index 0c9a40f..8480f10 100644
--- a/config/config.go
+++ b/config/config.go
@@ -104,6 +104,7 @@ type AccountConfig struct {
 	SignatureCmd      string
 	EnableFoldersSort bool     `ini:"enable-folders-sort"`
 	FoldersSort       []string `ini:"folders-sort" delim:","`
+	PgpKeyId          string   `ini:"pgp-key-id"`
 }
 
 type BindingConfig struct {
@@ -248,6 +249,8 @@ func loadAccountConfig(path string) ([]AccountConfig, error) {
 				account.Archive = val
 			} else if key == "enable-folders-sort" {
 				account.EnableFoldersSort, _ = strconv.ParseBool(val)
+			} else if key == "pgp-key-id" {
+				account.PgpKeyId = val
 			} else if key != "name" {
 				account.Params[key] = val
 			}
@@ -582,13 +585,14 @@ func validateBorderChars(section *ini.Section, config *UIConfig) error {
 
 func validatePgpProvider(section *ini.Section) error {
 	m := map[string]bool{
+		"gpg":      true,
 		"internal": true,
 	}
 	for key, val := range section.KeysHash() {
 		switch key {
 		case "pgp-provider":
 			if !m[strings.ToLower(val)] {
-				return fmt.Errorf("%v must be 'internal'", key)
+				return fmt.Errorf("%v must be either 'gpg' or 'internal'", key)
 			}
 		}
 	}