package/dropbear/0001-only-advertise-single-server-ecdsa-key-when-R-is-used.patch

# HG changeset patch
# User Matt Johnston <matt@ucc.asn.au>
# Date 1520519133 -28800
# Node ID 0dc3103a5900971d1d06d9101e062ddbd1112436
# Parent  0f149d63068d90705db7fb52c8dea15ff32eedd7
Only advertise a single server ecdsa key when -R (generate as required) is
specified. Fixes -R now that default ecdsa key size has changed.

Upstream-URL: https://secure.ucc.asn.au/hg/dropbear/rev/0dc3103a5900
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
diff -r 0f149d63068d -r 0dc3103a5900 svr-runopts.c
--- a/svr-runopts.c	Thu Mar 08 22:22:11 2018 +0800
+++ b/svr-runopts.c	Thu Mar 08 22:25:33 2018 +0800
@@ -526,8 +526,10 @@
 
 void load_all_hostkeys() {
 	int i;
-	int disable_unset_keys = 1;
 	int any_keys = 0;
+#ifdef DROPBEAR_ECDSA
+	int loaded_any_ecdsa = 0;
+#endif
 
 	svr_opts.hostkey = new_sign_key();
 
@@ -552,14 +554,8 @@
 #endif
 	}
 
-#if DROPBEAR_DELAY_HOSTKEY
-	if (svr_opts.delay_hostkey) {
-		disable_unset_keys = 0;
-	}
-#endif
-
 #if DROPBEAR_RSA
-	if (disable_unset_keys && !svr_opts.hostkey->rsakey) {
+	if (!svr_opts.delay_hostkey && !svr_opts.hostkey->rsakey) {
 		disablekey(DROPBEAR_SIGNKEY_RSA);
 	} else {
 		any_keys = 1;
@@ -567,39 +563,54 @@
 #endif
 
 #if DROPBEAR_DSS
-	if (disable_unset_keys && !svr_opts.hostkey->dsskey) {
+	if (!svr_opts.delay_hostkey && !svr_opts.hostkey->dsskey) {
 		disablekey(DROPBEAR_SIGNKEY_DSS);
 	} else {
 		any_keys = 1;
 	}
 #endif
 
+#if DROPBEAR_ECDSA
+	/* We want to advertise a single ecdsa algorithm size.
+	- If there is a ecdsa hostkey at startup we choose that that size.
+	- If we generate at runtime we choose the default ecdsa size.
+	- Otherwise no ecdsa keys will be advertised */
 
-#if DROPBEAR_ECDSA
+	/* check if any keys were loaded at startup */
+	loaded_any_ecdsa = 
+		0
 #if DROPBEAR_ECC_256
-	if ((disable_unset_keys || ECDSA_DEFAULT_SIZE != 256)
-		&& !svr_opts.hostkey->ecckey256) {
+		|| svr_opts.hostkey->ecckey256
+#endif
+#if DROPBEAR_ECC_384
+		|| svr_opts.hostkey->ecckey384
+#endif
+#if DROPBEAR_ECC_521
+		|| svr_opts.hostkey->ecckey521
+#endif
+		;
+	any_keys |= loaded_any_ecdsa;
+
+	/* Or an ecdsa key could be generated at runtime */
+	any_keys |= svr_opts.delay_hostkey;
+
+	/* At most one ecdsa key size will be left enabled */
+#if DROPBEAR_ECC_256
+	if (!svr_opts.hostkey->ecckey256
+		&& (!svr_opts.delay_hostkey || loaded_any_ecdsa || ECDSA_DEFAULT_SIZE != 256 )) {
 		disablekey(DROPBEAR_SIGNKEY_ECDSA_NISTP256);
-	} else {
-		any_keys = 1;
 	}
 #endif
-
 #if DROPBEAR_ECC_384
-	if ((disable_unset_keys || ECDSA_DEFAULT_SIZE != 384)
-		&& !svr_opts.hostkey->ecckey384) {
+	if (!svr_opts.hostkey->ecckey384
+		&& (!svr_opts.delay_hostkey || loaded_any_ecdsa || ECDSA_DEFAULT_SIZE != 384 )) {
 		disablekey(DROPBEAR_SIGNKEY_ECDSA_NISTP384);
-	} else {
-		any_keys = 1;
 	}
 #endif
-
 #if DROPBEAR_ECC_521
-	if ((disable_unset_keys || ECDSA_DEFAULT_SIZE != 521)
-		&& !svr_opts.hostkey->ecckey521) {
+	if (!svr_opts.hostkey->ecckey521
+		&& (!svr_opts.delay_hostkey || loaded_any_ecdsa || ECDSA_DEFAULT_SIZE != 521 )) {
 		disablekey(DROPBEAR_SIGNKEY_ECDSA_NISTP521);
-	} else {
-		any_keys = 1;
 	}
 #endif
 #endif /* DROPBEAR_ECDSA */