net: nfc: Propagate ISO14443 type A target ATS to userspace via netlink

Add a 20-byte field ats to struct nfc_target and expose it as
NFC_ATTR_TARGET_ATS via the netlink interface. The payload contains
'historical bytes' that help to distinguish cards from one another.
The information is commonly used to assemble an emulated ATR similar
to that reported by smart cards with contacts.

Add a 20-byte field target_ats to struct nci_dev to hold the payload
obtained in nci_rf_intf_activated_ntf_packet() and copy it to over to
nfc_target.ats in nci_activate_target(). The approach is similar
to the handling of 'general bytes' within ATR_RES.

Replace the hard-coded size of rats_res within struct
activation_params_nfca_poll_iso_dep by the equal constant NFC_ATS_MAXSIZE
now defined in nfc.h

Within NCI, the information corresponds to the 'RATS Response' activation
parameter that omits the initial length byte TL. This loses no
information and is consistent with our handling of SENSB_RES that
also drops the first (constant) byte.

Tested with nxp_nci_i2c on a few type A targets including an
ICAO 9303 compliant passport.

I refrain from the corresponding change to digital_in_recv_ats()
to have the few drivers based on digital.h fill nfc_target.ats,
as I have no way to test it. That class of drivers appear not to set
NFC_ATTR_TARGET_SENSB_RES either. Consider a separate patch to propagate
(all) the parameters.

Signed-off-by: Juraj Šarinay <juraj@sarinay.com>
Link: https://patch.msgid.link/20241103124525.8392-1-juraj@sarinay.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

3 files changed, 48 insertions, 2 deletions

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index f456a5911e7d..1ec5955fe469 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -757,6 +757,14 @@ int nci_core_conn_close(struct nci_dev *ndev, u8 conn_id)
 }
 EXPORT_SYMBOL(nci_core_conn_close);
 
+static void nci_set_target_ats(struct nfc_target *target, struct nci_dev *ndev)
+{
+	if (ndev->target_ats_len > 0) {
+		target->ats_len = ndev->target_ats_len;
+		memcpy(target->ats, ndev->target_ats, target->ats_len);
+	}
+}
+
 static int nci_set_local_general_bytes(struct nfc_dev *nfc_dev)
 {
 	struct nci_dev *ndev = nfc_get_drvdata(nfc_dev);
@@ -939,8 +947,11 @@ static int nci_activate_target(struct nfc_dev *nfc_dev,
 				 msecs_to_jiffies(NCI_RF_DISC_SELECT_TIMEOUT));
 	}
 
-	if (!rc)
+	if (!rc) {
 		ndev->target_active_prot = protocol;
+		if (protocol == NFC_PROTO_ISO14443)
+			nci_set_target_ats(target, ndev);
+	}
 
 	return rc;
 }
diff --git a/net/nfc/nci/ntf.c b/net/nfc/nci/ntf.c
index 994a0a1efb58..a818eff27e6b 100644
--- a/net/nfc/nci/ntf.c
+++ b/net/nfc/nci/ntf.c
@@ -402,7 +402,7 @@ static int nci_extract_activation_params_iso_dep(struct nci_dev *ndev,
 	switch (ntf->activation_rf_tech_and_mode) {
 	case NCI_NFC_A_PASSIVE_POLL_MODE:
 		nfca_poll = &ntf->activation_params.nfca_poll_iso_dep;
-		nfca_poll->rats_res_len = min_t(__u8, *data++, 20);
+		nfca_poll->rats_res_len = min_t(__u8, *data++, NFC_ATS_MAXSIZE);
 		pr_debug("rats_res_len %d\n", nfca_poll->rats_res_len);
 		if (nfca_poll->rats_res_len > 0) {
 			memcpy(nfca_poll->rats_res,
@@ -531,6 +531,28 @@ static int nci_store_general_bytes_nfc_dep(struct nci_dev *ndev,
 	return NCI_STATUS_OK;
 }
 
+static int nci_store_ats_nfc_iso_dep(struct nci_dev *ndev,
+				     const struct nci_rf_intf_activated_ntf *ntf)
+{
+	ndev->target_ats_len = 0;
+
+	if (ntf->activation_params_len <= 0)
+		return NCI_STATUS_OK;
+
+	if (ntf->activation_params.nfca_poll_iso_dep.rats_res_len > NFC_ATS_MAXSIZE) {
+		pr_debug("ATS too long\n");
+		return NCI_STATUS_RF_PROTOCOL_ERROR;
+	}
+
+	if (ntf->activation_params.nfca_poll_iso_dep.rats_res_len > 0) {
+		ndev->target_ats_len = ntf->activation_params.nfca_poll_iso_dep.rats_res_len;
+		memcpy(ndev->target_ats, ntf->activation_params.nfca_poll_iso_dep.rats_res,
+		       ndev->target_ats_len);
+	}
+
+	return NCI_STATUS_OK;
+}
+
 static void nci_rf_intf_activated_ntf_packet(struct nci_dev *ndev,
 					     const struct sk_buff *skb)
 {
@@ -660,6 +682,14 @@ exit:
 			if (err != NCI_STATUS_OK)
 				pr_err("unable to store general bytes\n");
 		}
+
+		/* store ATS to be reported later in nci_activate_target */
+		if (ntf.rf_interface == NCI_RF_INTERFACE_ISO_DEP &&
+		    ntf.activation_rf_tech_and_mode == NCI_NFC_A_PASSIVE_POLL_MODE) {
+			err = nci_store_ats_nfc_iso_dep(ndev, &ntf);
+			if (err != NCI_STATUS_OK)
+				pr_err("unable to store ATS\n");
+		}
 	}
 
 	if (!(ntf.activation_rf_tech_and_mode & NCI_RF_TECH_MODE_LISTEN_MASK)) {
diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index dd2ce73a24fb..6a40b8d0350d 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -96,6 +96,11 @@ static int nfc_genl_send_target(struct sk_buff *msg, struct nfc_target *target,
 			goto nla_put_failure;
 	}
 
+	if (target->ats_len > 0 &&
+	    nla_put(msg, NFC_ATTR_TARGET_ATS, target->ats_len,
+		    target->ats))
+		goto nla_put_failure;
+
 	genlmsg_end(msg, hdr);
 	return 0;