cmd/age: automatically load default SSH key paths

cmd/age/age.go

@@ -12,6 +12,7 @@ import (
 	"flag"
 	"fmt"
 	"io"
+	"io/ioutil"
 	_log "log"
 	"os"
 	"runtime/debug"
@@ -292,8 +293,26 @@ func decrypt(keys []string, in io.Reader, out io.Writer) {
 		&LazyScryptIdentity{passphrasePrompt},
 	}
 
-	// TODO: check the default SSH location if no arguments are provided
-	// (~/.ssh/id_rsa, ~/.ssh/id_ed25519).
+	// If they exist and are well-formed, load the default SSH keys. If they are
+	// passphrase protected, the passphrase will only be requested if the
+	// identity matches a recipient stanza.
+	for _, path := range []string{
+		os.ExpandEnv("$HOME/.ssh/id_rsa"),
+		os.ExpandEnv("$HOME/.ssh/id_ed25519"),
+	} {
+		content, err := ioutil.ReadFile(path)
+		if err != nil {
+			continue
+		}
+		ids, err := parseSSHIdentity(path, content)
+		if err != nil {
+			// If the key is explicitly requested, this error will be caught
+			// below, otherwise ignore it silently.
+			continue
+		}
+		identities = append(identities, ids...)
+	}
+
 	for _, name := range keys {
 		ids, err := parseIdentitiesFile(name)
 		if err != nil {