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Add HMAC/IP support for different remote IP's through proxies & Cloud… #49

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Add HMAC/IP support for different remote IP's through proxies & Cloud… #49

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38 changes: 32 additions & 6 deletions src/AntiCSRF.php
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Original file line number Diff line number Diff line change
Expand Up @@ -280,9 +280,7 @@ public function getTokenArray(string $lockTo = ''): array
$token = Base64UrlSafe::encode(
\hash_hmac(
$this->hashAlgo,
isset($this->server['REMOTE_ADDR'])
? (string) $this->server['REMOTE_ADDR']
: '127.0.0.1',
$this->getRemoteIP(),
(string) Base64UrlSafe::decode($token),
true
)
Expand Down Expand Up @@ -407,9 +405,7 @@ public function validateRequestOrThrow()
$expected = Base64UrlSafe::encode(
\hash_hmac(
$this->hashAlgo,
isset($this->server['REMOTE_ADDR'])
? (string) $this->server['REMOTE_ADDR']
: '127.0.0.1',
$this->getRemoteIP(),
(string) Base64UrlSafe::decode((string) $stored['token']),
true
)
Expand Down Expand Up @@ -548,4 +544,34 @@ protected static function noHTML(string $untrusted): string
{
return \htmlentities($untrusted, ENT_QUOTES, 'UTF-8');
}

/**
* Wrapper to support different sources of remote IP addresses.
*
* @return string
*/
protected function getRemoteIP(): string
{
if (isset($this->server["HTTP_CF_CONNECTING_IP"]) && filter_var($this->server["HTTP_CF_CONNECTING_IP"], FILTER_VALIDATE_IP))
{
return $this->server["HTTP_CF_CONNECTING_IP"];
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What if an attacker specifies a fake header here after discovering the server's real IP?

What if an attacker specifies this header for a non-CloudFlare IP?

Etc.

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Would you suggest validating against the REMOTE_ADDR to the CloudFlare IP ranges? https://www.cloudflare.com/ips/

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Yes, and this can be hard-coded. We can update it in the future if their list of IPs widens.

}

if (isset($this->server["HTTP_X_FORWARDED_FOR"]) && filter_var($this->server["HTTP_X_FORWARDED_FOR"], FILTER_VALIDATE_IP))
{
return $this->server["HTTP_X_FORWARDED_FOR"];
}
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Attackers can lie about X-Forwarded-For. This should be guarded by a configuration setting.

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What would you suggest? A configuration setting as in hmac_ip_allow_x_forwarded_for? Or something more general that would include both this option as well as CloudFlare for example?

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Yes, a configuration setting would be a good idea. Let people opt into this behavior.


if (isset($this->server["HTTP_CLIENT_IP"]) && filter_var($this->server["HTTP_CLIENT_IP"], FILTER_VALIDATE_IP))
{
return $this->server["HTTP_CLIENT_IP"];
}

if (isset($this->server['REMOTE_ADDR']))
{
return $this->server['REMOTE_ADDR'];
}

return '127.0.0.1';
}
}