config: keep cache of resolved credential commands

outgoing-cred-cmd is used to retrieve the password from a password
manager such as UNIX pass or bitwarden CLI. These tools often prompt for
a passphrase to secure the passwords and it is annoying having to enter
it every time sending an email with aerc.

Add a new option outgoing-cred-cmd-cache (default to true) to control
whether aerc will keep a cache of the password or run outgoing-cred-cmd
every time an email needs to be sent.

NB: If the cached password is incorrect, the only way to change it is to
restart aerc.

Fixes: ca90343850 ("outgoing-cred-cmd: delay execution until an email needs to be sent")
Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Moritz Poldrack <moritz@poldrack.dev>

CHANGELOG.md

@@ -5,6 +5,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased](https://git.sr.ht/~rjarry/aerc/log/master)
 
+### Fixed
+
+- `outgoing-cred-cmd` will no longer be executed every time an email needs to
+  be sent. The output will be stored until aerc is shut down. This behaviour
+  can be disabled by setting `outgoing-cred-cmd-cache=false` in
+  `accounts.conf`.
+
 ## [0.12.0](https://git.sr.ht/~rjarry/aerc/refs/0.12.0) - 2022-09-01
 
 ### Added

config/config.go

@@ -98,13 +98,15 @@ const (
 type RemoteConfig struct {
 	Value       string
 	PasswordCmd string
+	CacheCmd    bool
+	cache       string
 }
 
-func (c RemoteConfig) parseValue() (*url.URL, error) {
+func (c *RemoteConfig) parseValue() (*url.URL, error) {
 	return url.Parse(c.Value)
 }
 
-func (c RemoteConfig) ConnectionString() (string, error) {
+func (c *RemoteConfig) ConnectionString() (string, error) {
 	if c.Value == "" || c.PasswordCmd == "" {
 		return c.Value, nil
 	}
@@ -124,18 +126,23 @@ func (c RemoteConfig) ConnectionString() (string, error) {
 		return c.Value, nil
 	}
 
+	pw := c.cache
+
+	if pw == "" {
 		cmd := exec.Command("sh", "-c", c.PasswordCmd)
 		cmd.Stdin = os.Stdin
 		output, err := cmd.Output()
 		if err != nil {
 			return "", fmt.Errorf("failed to read password: %w", err)
 		}
-
-	pw := strings.TrimSpace(string(output))
+		pw = strings.TrimSpace(string(output))
+	}
 	u.User = url.UserPassword(u.User.Username(), pw)
-	c.Value = u.String()
+	if c.CacheCmd {
+		c.cache = pw
+	}
 
-	return c.Value, nil
+	return u.String(), nil
 }
 
 type AccountConfig struct {
@@ -314,6 +321,13 @@ func loadAccountConfig(path string, accts []string) ([]AccountConfig, error) {
 				account.Outgoing.Value = val
 			case "outgoing-cred-cmd":
 				account.Outgoing.PasswordCmd = val
+			case "outgoing-cred-cmd-cache":
+				cache, err := strconv.ParseBool(val)
+				if err != nil {
+					return nil, fmt.Errorf(
+						"%s=%s %w", key, val, err)
+				}
+				account.Outgoing.CacheCmd = cache
 			case "from":
 				account.From = val
 			case "aliases":

doc/aerc-config.5.scd

@@ -657,6 +657,13 @@ Note that many of these configuration options are written for you, such as
 
 	Default: none
 
+*outgoing-cred-cmd-cache*
+	By default, the credentials returned by the command will be cached until
+	aerc is shut down. If set to false, *outgoing-cred-cmd* will be executed
+	every time an email is to be sent.
+
+	Default: true
+
 *pgp-auto-sign*
 	If true, all outgoing emails from this account will be signed (if a signing
 	key is available)