Allow specifying full private key

sbotc.1

@@ -19,7 +19,7 @@
 |
 .Op Fl c Ar cap
 .Op Fl k Ar key
-.Op Fl K Ar keypair_seed
+.Op Fl K Ar keypair
 .Oc
 .
 .Oo
@@ -91,8 +91,8 @@ and
 .It Fl k Ar key
 The key to connect to. Default is your public key, as read from your
 private key file.
-.It Fl K Ar keypair_seed
-Private key seed to use for secret-handshake. Default is to use the private key
+.It Fl K Ar keypair
+Private key or private key seed to use for secret-handshake. Default is to use the private key
 from your
 .Pa ~/.ssb/secret
 file or other secret file according to the environmental variables described in

sbotc.c

@@ -394,6 +394,15 @@ static int pubkey_decode(const char *key_str, unsigned char key[32]) {
 	return base64_decode(key_str, 44, key, 32);
 }
 
+static int seckey_decode(const char *key_str, unsigned char key[64]) {
+	if (!key_str) { errno = EPROTO; return -1; }
+	if (!*key_str) { errno = EPROTO; return -1; }
+	if (*key_str == '@') key_str++;
+	size_t len = strlen(key_str);
+	if (len > 8 && memcmp(key_str + len - 8, ".ed25519", 8) == 0) len -= 8;
+	return base64_decode(key_str, len, key, 64);
+}
+
 static jsmntok_t *json_lookup(const char *buf, jsmntok_t *tok, const char *prop, size_t prop_len) {
 	jsmntok_t *end = tok + tok->size + 1;
 	if (tok->type != JSMN_OBJECT) { errno = EPROTO; return NULL; }
@@ -1134,7 +1143,14 @@ int main(int argc, char *argv[]) {
 		if (rc < 0) errx(0, "unable to convert method name");
 	}
 
-	if (keypair_seed_str) {
+	if (keypair_seed_str == NULL) {
+		read_private_key(app_dir, private_key);
+		memcpy(public_key, private_key+32, 32);
+	} else if (strlen(keypair_seed_str) > 55) {
+		rc = seckey_decode(keypair_seed_str, private_key);
+		if (rc < 0) err(1, "unable to decode private key");
+		memcpy(public_key, private_key+32, 32);
+	} else if (keypair_seed_str) {
 		unsigned char seed[crypto_sign_SEEDBYTES];
 		unsigned char ed25519_skpk[crypto_sign_ed25519_SECRETKEYBYTES];
 
@@ -1144,9 +1160,6 @@ int main(int argc, char *argv[]) {
 		if (rc < 0) err(1, "unable to convert private key to seed");
 		rc = crypto_sign_seed_keypair(public_key, private_key, seed);
 		if (rc < 0) err(1, "unable to generate keypair from seed");
-	} else {
-		read_private_key(app_dir, private_key);
-		memcpy(public_key, private_key+32, 32);
 	}
 
 	if (key) {