[PATCH 02/13] ie: add ie_parse_owe_transition_from_data

[PATCH 02/13] ie: add ie_parse_owe_transition_from_data

[James Prestwood]

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This is a parser for the WFA OWE Transition element. For now the
optional band/channel bytes will not be parsed as hostapd does not
yet support these and would also require the 802.11 appendix E-1
to be added to IWD. Because of this OWE Transition networks are
assumed to be on the same channel as their open counterpart.
---
 src/ie.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 src/ie.h |  3 +++
 2 files changed, 46 insertions(+)

diff --git a/src/ie.c b/src/ie.c
index 1ce1d8a5..286b6a49 100644
--- a/src/ie.c
+++ b/src/ie.c
@@ -1343,6 +1343,8 @@ bool is_ie_wfa_ie(const uint8_t *data, uint8_t len, uint8_t oi_type)
 		return false;
 	else if (oi_type == IE_WFA_OI_HS20_INDICATION && len != 5 && len != 7)
 		return false;
+	else if (oi_type == IE_WFA_OI_OWE_TRANSITION && len < 12)
+		return false;
 	else if (len < 4) /* OI not handled, but at least check length */
 		return false;
 
@@ -2492,3 +2494,44 @@ int ie_parse_network_cost(const void *data, size_t len,
 	*flags = l_get_le16(ie + 8);
 	return 0;
 }
+
+int ie_parse_owe_transition(const void *data, size_t len, uint8_t *bssid,
+				char ssid[33])
+{
+	const uint8_t *ie = data;
+	size_t slen;
+
+	if (len < 14 || ie[0] != IE_TYPE_VENDOR_SPECIFIC)
+		return -ENOMSG;
+
+	if (!is_ie_wfa_ie(ie + 2, len - 2, IE_WFA_OI_OWE_TRANSITION))
+		return -ENOMSG;
+
+	slen = l_get_u8(ie + 12);
+	if (slen > 32)
+		return -ENOMSG;
+
+	/*
+	 * WFA OWE Specification 2.3.1
+	 *
+	 * "Band Info and Channel Info are optional fields. If configured,
+	 * both fields shall be included in an OWE Transition Mode element"
+	 *
+	 * TODO: Support Band/Channel bytes:
+	 * For the time being the OWE transition AP is assumed to be on the same
+	 * channel as the open AP. This means there should be no band/channel
+	 * bytes at the end of the IE. Currently hostapd has no support for this
+	 * so it can be skipped. In addition 802.11 Appendix E-1 needs to be
+	 * encoded as a table to map Country/operating class to channels to make
+	 * any sense of it.
+	 */
+	if (len != slen + 13)
+		return -ENOMSG;
+
+	memcpy(bssid, ie + 6, 6);
+
+	memcpy(ssid, ie + 13, slen);
+	ssid[slen] = '\0';
+
+	return 0;
+}
diff --git a/src/ie.h b/src/ie.h
index 4e1c5433..fdd7f34c 100644
--- a/src/ie.h
+++ b/src/ie.h
@@ -630,3 +630,6 @@ void ie_build_fils_ip_addr_response(
 
 int ie_parse_network_cost(const void *data, size_t len,
 				uint16_t *flags, uint16_t *level);
+
+int ie_parse_owe_transition(const void *data, size_t len, uint8_t *bssid,
+				char ssid[33]);
-- 
2.31.1

Re: [PATCH 02/13] ie: add ie_parse_owe_transition_from_data

[Denis Kenzior]

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> See [1] for reasons why
> 

Whoops, I guess I forgot to include [1].  Here it is:
https://hamberg.no/erlend/posts/2013-02-18-static-array-indices.html

Regards,
-Denis

Re: [PATCH 02/13] ie: add ie_parse_owe_transition_from_data

[Denis Kenzior]

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Hi James,

On 9/15/21 12:36 PM, James Prestwood wrote:
> This is a parser for the WFA OWE Transition element. For now the
> optional band/channel bytes will not be parsed as hostapd does not
> yet support these and would also require the 802.11 appendix E-1
> to be added to IWD. Because of this OWE Transition networks are
> assumed to be on the same channel as their open counterpart.
> ---
>   src/ie.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>   src/ie.h |  3 +++
>   2 files changed, 46 insertions(+)
> 

<snip>

> +
> +int ie_parse_owe_transition(const void *data, size_t len, uint8_t *bssid,
> +				char ssid[33])

Can we change the signature as follows:
int ie_parse_owe_transition(const void *data,
		size_t len,
		uint8_t out_bssid[static 6],
		char out_ssid[static 33])

See [1] for reasons why

> +{
> +	const uint8_t *ie = data;
> +	size_t slen;
> +
> +	if (len < 14 || ie[0] != IE_TYPE_VENDOR_SPECIFIC)
> +		return -ENOMSG;
> +
> +	if (!is_ie_wfa_ie(ie + 2, len - 2, IE_WFA_OI_OWE_TRANSITION))
> +		return -ENOMSG;
> +
> +	slen = l_get_u8(ie + 12);
> +	if (slen > 32)
> +		return -ENOMSG;
> +
> +	/*
> +	 * WFA OWE Specification 2.3.1
> +	 *
> +	 * "Band Info and Channel Info are optional fields. If configured,
> +	 * both fields shall be included in an OWE Transition Mode element"
> +	 *
> +	 * TODO: Support Band/Channel bytes:
> +	 * For the time being the OWE transition AP is assumed to be on the same
> +	 * channel as the open AP. This means there should be no band/channel
> +	 * bytes at the end of the IE. Currently hostapd has no support for this
> +	 * so it can be skipped. In addition 802.11 Appendix E-1 needs to be
> +	 * encoded as a table to map Country/operating class to channels to make
> +	 * any sense of it.
> +	 */
> +	if (len != slen + 13)
> +		return -ENOMSG;
> +
> +	memcpy(bssid, ie + 6, 6);
> +
> +	memcpy(ssid, ie + 13, slen);
> +	ssid[slen] = '\0';

So we have to be careful here since ssid is not guaranteed to be utf8.  This is 
why the scan_bss and handshake_state structures store ssid + length.  For 
anything user-visible we enforce SSID to be UTF8, but in the case of OWE Hidden 
BSS it should be acceptable to have an SSID that isn't.

Regards,
-Denis