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anqp: rework NAI Realm parsing 

The initial ANQP parser design did not work well with how the hotspot
implementation was turning out. For one, much care was taken into parsing
the EAP credentials which are not really required. The assumption is
that any hotspot network will already be provisioned, so checking that
the EAP parameters match is a bit overkill. Instead only the NAI Realms
will be checked. This greatly simplifies the NAI realm parser, as now it
can just return a string list of realms instead of the full EAP
credential info.
This commit is contained in:
James Prestwood 2019-06-26 12:20:32 -07:00 committed by Denis Kenzior
parent a5f2710d05
commit 537fcd12ca
2 changed files with 15 additions and 182 deletions
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182
src/anqp.c
View File

@ -128,167 +128,9 @@ bool anqp_iter_is_hs20(const struct anqp_iter *iter, uint8_t *stype,
return true;
}
static bool parse_eap_params(const unsigned char *anqp, unsigned int len,
uint8_t *method, uint8_t *non_eap_inner,
uint8_t *eap_inner, uint8_t *credential,
uint8_t *tunneled_credential)
{
uint8_t param_count;
if (len < 2)
return false;
*method = *anqp++;
param_count = *anqp++;
len -= 2;
*non_eap_inner = 0;
*eap_inner = 0;
*credential = 0;
*tunneled_credential = 0;
while (param_count--) {
uint8_t ap_id;
uint8_t ap_len;
if (len < 2)
return false;
ap_id = *anqp++;
ap_len = *anqp++;
len -= 2;
if (len < ap_len)
return false;
switch (ap_id) {
case ANQP_AP_NON_INNER_AUTH_EAP:
*non_eap_inner = *anqp;
break;
case ANQP_AP_INNER_AUTH_EAP:
*eap_inner = *anqp;
break;
case ANQP_AP_CREDENTIAL:
*credential = *anqp;
break;
case ANQP_AP_TUNNELED_EAP_CREDENTIAL:
*tunneled_credential = *anqp;
break;
case ANQP_AP_EXPANDED_EAP_METHOD:
case ANQP_AP_EXPANDED_INNER_EAP_METHOD:
case ANQP_AP_VENDOR_SPECIFIC:
break;
}
anqp += ap_len;
len -= ap_len;
}
return true;
}
/*
* Parses an EAP ANQP list.
*/
static bool parse_eap(const unsigned char *anqp, unsigned int len,
const char *nai, bool hs20,
struct anqp_eap_method *method_out)
{
uint8_t eap_count;
if (len < 1)
return false;
eap_count = *anqp++;
len--;
while (eap_count--) {
uint8_t eap_len;
uint8_t method;
uint8_t non_eap_inner;
uint8_t eap_inner;
uint8_t credential;
uint8_t tunneled_credential;
if (len < 1)
return false;
eap_len = *anqp++;
len--;
if (!parse_eap_params(anqp, eap_len,
&method, &non_eap_inner,
&eap_inner, &credential,
&tunneled_credential))
return false;
if (hs20) {
/*
* TODO: Support EAP-SIM/AKA/AKA' with Hotspot
*/
if (method != EAP_TYPE_TTLS) {
l_debug("EAP method %u not supported", method);
goto next;
}
/* MSCHAPv2 */
if (non_eap_inner != 4) {
l_debug("Non-EAP inner %u not supported",
non_eap_inner);
goto next;
}
/* username/password */
if (credential != 7) {
l_debug("credential type %u not supported",
credential);
goto next;
}
} else {
/* can't use methods without user/password */
if (credential != 7 && tunneled_credential != 7)
goto next;
}
method_out->method = method;
/* nai is guarenteed to NULL terminate and be < 256 bytes */
l_strlcpy(method_out->realm, nai, sizeof(method_out->realm));
method_out->non_eap_inner = non_eap_inner;
method_out->eap_inner = eap_inner;
method_out->credential = credential;
method_out->tunneled_credential = tunneled_credential;
return true;
next:
if (len < eap_len)
return false;
anqp += eap_len;
len -= eap_len;
}
return false;
}
/*
* Parses NAI Realm ANQP-element. The code here parses the NAI Realm until an
* acceptable EAP method is found. Once a method is found it is returned via
* method_out. The structure of NAI realm is such that it does not allow for a
* convenient static structure (several nested lists). Since we can only handle
* EAP methods with user/password credentials anyways it makes sense to just
* return the first EAP method found that meets our criteria. In addition, this
* is only being used for Hotspot 2.0, which mandates EAP-TLS/TTLS/SIM/AKA,
* meaning TTLS is the only contender for this parsing.
*
* @param hs20 true if this parsing is for a Hotspot 2.0 network. This will
* restrict what EAP method info is chosen as to comply with the
* Hotspot 2.0 spec (i.e. EAP-TTLS w/ MSCHAPv2 or SIM/AKA/AKA').
*/
bool anqp_parse_nai_realm(const unsigned char *anqp, unsigned int len,
bool hs20, struct anqp_eap_method *method_out)
char **anqp_parse_nai_realms(const unsigned char *anqp, unsigned int len)
{
char **realms = NULL;
uint16_t count;
if (len < 2)
@ -299,6 +141,8 @@ bool anqp_parse_nai_realm(const unsigned char *anqp, unsigned int len,
anqp += 2;
len -= 2;
l_debug("");
while (count--) {
uint16_t realm_len;
uint8_t encoding;
@ -315,7 +159,7 @@ bool anqp_parse_nai_realm(const unsigned char *anqp, unsigned int len,
*/
if (len < 4)
return false;
goto failed;
realm_len = l_get_le16(anqp);
anqp += 2;
@ -326,7 +170,7 @@ bool anqp_parse_nai_realm(const unsigned char *anqp, unsigned int len,
nai_len = anqp[1];
if (len - 2 < nai_len)
return false;
goto failed;
memcpy(nai_realm, anqp + 2, nai_len);
@ -342,19 +186,21 @@ bool anqp_parse_nai_realm(const unsigned char *anqp, unsigned int len,
l_warn("Not verifying NAI encoding");
else if (!l_utf8_validate(nai_realm, nai_len, NULL)) {
l_warn("NAI is not UTF-8");
return false;
goto failed;
}
if (parse_eap(anqp + 2 + nai_len, realm_len - 2 - nai_len,
nai_realm, hs20, method_out))
return true;
realms = l_strv_append(realms, nai_realm);
if (len < realm_len)
return false;
goto failed;
anqp += realm_len;
len -= realm_len;
}
return false;
return realms;
failed:
l_strv_free(realms);
return NULL;
}

15
src/anqp.h
View File

@ -93,18 +93,6 @@ struct anqp_iter {
const unsigned char *data;
};
/*
* TODO: Support expanded EAP types
*/
struct anqp_eap_method {
char realm[256];
uint8_t method;
uint8_t non_eap_inner;
uint8_t eap_inner;
uint8_t credential;
uint8_t tunneled_credential;
};
void anqp_iter_init(struct anqp_iter *iter, const unsigned char *anqp,
unsigned int len);
bool anqp_iter_next(struct anqp_iter *iter, uint16_t *id, uint16_t *len,
@ -113,5 +101,4 @@ bool anqp_iter_is_hs20(const struct anqp_iter *iter, uint8_t *stype,
unsigned int *len, const unsigned char **data);
bool anqp_hs20_parse_osu_provider_nai(const unsigned char *anqp,
unsigned int len, const char **nai_out);
bool anqp_parse_nai_realm(const unsigned char *anqp, unsigned int len,
bool hs20, struct anqp_eap_method *method);
char **anqp_parse_nai_realms(const unsigned char *anqp, unsigned int len);