[PATCH v2 1/4] network: add support for SAE password identifiers

[James Prestwood <prestwoj@gmail.com>]

Adds a new network profile setting [Security].PasswordIdentifier.
When set (and the BSS enables SAE password identifiers) the network
and handshake object will read this and use it for the SAE
exchange.

Loading the PSK will fail if there is no password identifier set
and the BSS sets the "exclusive" bit. If a password identifier is
set and the BSS doesn't indicate support the setting will be ignored
(with a debug print).
---
 src/network.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/src/network.c b/src/network.c
index 79f964b2..70a5434b 100644
--- a/src/network.c
+++ b/src/network.c
@@ -70,6 +70,7 @@ struct network {
 	struct network_info *info;
 	unsigned char *psk;
 	char *passphrase;
+	char *password_identifier;
 	struct l_ecc_point *sae_pt_19; /* SAE PT for Group 19 */
 	struct l_ecc_point *sae_pt_20; /* SAE PT for Group 20 */
 	unsigned int agent_request;
@@ -124,6 +125,13 @@ static void network_reset_passphrase(struct network *network)
 		network->passphrase = NULL;
 	}
 
+	if (network->password_identifier) {
+		explicit_bzero(network->password_identifier,
+				strlen(network->password_identifier));
+		l_free(network->password_identifier);
+		network->password_identifier = NULL;
+	}
+
 	if (network->sae_pt_19) {
 		l_ecc_point_free(network->sae_pt_19);
 		network->sae_pt_19 = NULL;
@@ -317,7 +325,8 @@ static struct l_ecc_point *network_generate_sae_pt(struct network *network,
 	l_debug("Generating PT for Group %u", group);
 
 	pt = crypto_derive_sae_pt_ecc(group, network->ssid,
-						network->passphrase, NULL);
+						network->passphrase,
+						network->password_identifier);
 	if (!pt)
 		l_warn("SAE PT generation for Group %u failed", group);
 
@@ -462,6 +471,10 @@ static int network_set_handshake_secrets_psk(struct network *network,
 
 		handshake_state_set_passphrase(hs, network->passphrase);
 
+		if (network->password_identifier)
+			handshake_state_set_password_identifier(hs,
+						network->password_identifier);
+
 		if (ie_rsnxe_capable(hs->authenticator_rsnxe,
 							IE_RSNX_SAE_H2E)) {
 			l_debug("Authenticator is SAE H2E capable");
@@ -631,6 +644,9 @@ static int network_load_psk(struct network *network, struct scan_bss *bss)
 	_auto_(l_free) char *passphrase =
 			l_settings_get_string(network->settings,
 						"Security", "Passphrase");
+	_auto_(l_free) char *password_id =
+			l_settings_get_string(network->settings, "Security",
+						"PasswordIdentifier");
 	_auto_(l_free) char *path =
 		storage_get_network_file_path(security, ssid);
 
@@ -641,6 +657,31 @@ static int network_load_psk(struct network *network, struct scan_bss *bss)
 		psk_len = 0;
 	}
 
+	if (is_sae) {
+		/*
+		 * Fail if:
+		 *   - the BSS exclusively uses password IDs and the profile
+		 *     does not have one set.
+		 *   - the BSS does not use password IDs and the profile has
+		 *     one set.
+		 *
+		 * In theory you could have a network with a mix of BSS's that
+		 * use IDs and those that don't, but this is a strange
+		 * configuration (arguably broken).
+		 */
+		if (bss->sae_pw_id_exclusive && !password_id) {
+			l_error("[Security].PasswordIdentifier is not set but "
+				"BSS requires SAE password identifiers");
+			return -ENOKEY;
+		}
+
+		if (!bss->sae_pw_id_used && password_id) {
+			l_debug("[Security].PasswordIdentifier set but BSS "
+				"does not not use password identifiers");
+			return -ENOKEY;
+		}
+	}
+
 	/* PSK can be generated from the passphrase but not the other way */
 	if (!psk || is_sae) {
 		if (!passphrase)
@@ -655,6 +696,7 @@ static int network_load_psk(struct network *network, struct scan_bss *bss)
 	network_reset_passphrase(network);
 	network_reset_psk(network);
 	network->passphrase = l_steal_ptr(passphrase);
+	network->password_identifier = l_steal_ptr(password_id);
 
 	if (network_settings_load_pt_ecc(network, path,
 						19, &network->sae_pt_19) > 0)
@@ -726,6 +768,11 @@ static void network_settings_save(struct network *network,
 		l_settings_set_string(settings, "Security", "Passphrase",
 					network->passphrase);
 
+	if (network->password_identifier)
+		l_settings_set_string(settings, "Security",
+					"PasswordIdentifier",
+					network->password_identifier);
+
 	if (network->sae_pt_19)
 		network_settings_save_sae_pt_ecc(settings, network->sae_pt_19);
 
-- 
2.34.1