flywp / includes / MagicLoginToken.php

MagicLoginToken.php in FlyWP Helper – Page Cache, Page Optimization, Emails for FlyWP Server Control Panel 1.7.0, at includes/MagicLoginToken.php

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1	<?php
2
3	namespace FlyWP;
4
5	/**
6	* Verifier for the signed, single-use tokens the FlyWP control plane mints for magic login.
7	*
8	* The format is a contract shared with the control plane, so it lives in one place with no
9	* WordPress dependency and can be tested on its own.
10	*
11	* flywp-ed25519.<b64url(payload_json)>.<b64url(ed25519_signature)>
12	*
13	* Two rules when changing this: the prefix is part of the signed material, and the signature is
14	* verified against the payload bytes as received, never against a re-encoding of the claims.
15	*
16	* @since 1.7.0
17	*/
18	class MagicLoginToken {
19
20	/**
21	* Token version. Part of the signed material.
22	*/
23	const VERSION = 'flywp-ed25519';
24
25	/**
26	* Longest token accepted, in bytes. Bounds the work done before the signature check.
27	*/
28	const MAX_LENGTH = 4096;
29
30	/**
31	* Longest lifetime a token may claim for itself, in seconds.
32	*/
33	const MAX_LIFETIME = 600;
34
35	/**
36	* Clock drift tolerated between the control plane and this site, in seconds.
37	*/
38	const DEFAULT_SKEW = 60;
39
40	/**
41	* Verify a token and return the claims it carries.
42	*
43	* @param string $token Raw token as it arrived in the request.
44	* @param string $public_key This site's FLYWP_LOGIN_PUBLIC_KEY (base64).
45	* @param int $now Current unix timestamp.
46	* @param int $skew Clock drift to tolerate, in seconds.
47	*
48	* @return array\|null The claims, or null when the token is not acceptable for any reason.
49	*/
50	public static function parse( $token, $public_key, $now, $skew = self::DEFAULT_SKEW ) {
51	if ( ! is_string( $token ) \|\| $token === '' \|\| strlen( $token ) > self::MAX_LENGTH ) {
52	return null;
53	}
54
55	$parts = explode( '.', $token );
56
57	if ( count( $parts ) !== 3 \|\| $parts[0] !== self::VERSION ) {
58	return null;
59	}
60
61	// Verify before reading any claim.
62	if ( ! self::verify( $parts[0] . '.' . $parts[1], $parts[2], $public_key ) ) {
63	return null;
64	}
65
66	$payload = self::base64url_decode( $parts[1] );
67	$claims = $payload === null ? null : json_decode( $payload, true );
68
69	if ( ! is_array( $claims ) \|\| ! self::has_valid_claims( $claims ) ) {
70	return null;
71	}
72
73	return self::is_fresh( $claims, (int) $now, (int) $skew ) ? $claims : null;
74	}
75
76	/**
77	* Whether this site's key vouches for the signature over $signed_material.
78	*
79	* Lengths are checked before the libsodium call, which throws on a wrong-size key or
80	* signature. Keep those checks.
81	*
82	* @param string $signed_material Bytes the signature is supposed to cover.
83	* @param string $encoded_signature Signature segment, base64url.
84	* @param string $public_key This site's FLYWP_LOGIN_PUBLIC_KEY (base64).
85	*
86	* @return bool
87	*/
88	private static function verify( $signed_material, $encoded_signature, $public_key ) {
89	// A host can be built without sodium; refuse rather than skip the check.
90	if ( ! function_exists( 'sodium_crypto_sign_verify_detached' ) ) {
91	return false;
92	}
93
94	if ( ! is_string( $public_key ) \|\| $public_key === '' ) {
95	return false;
96	}
97
98	$signature = self::base64url_decode( $encoded_signature );
99
100	// phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode
101	$raw_public_key = base64_decode( $public_key, true );
102
103	if ( $signature === null \|\| strlen( $signature ) !== SODIUM_CRYPTO_SIGN_BYTES ) {
104	return false;
105	}
106
107	if ( $raw_public_key === false \|\| strlen( $raw_public_key ) !== SODIUM_CRYPTO_SIGN_PUBLICKEYBYTES ) {
108	return false;
109	}
110
111	return sodium_crypto_sign_verify_detached( $signature, $signed_material, $raw_public_key );
112	}
113
114	/**
115	* Whether every claim is present and of the right type.
116	*
117	* @param array $claims Decoded claims.
118	*
119	* @return bool
120	*/
121	private static function has_valid_claims( array $claims ) {
122	foreach ( [ 'sub', 'sid', 'iat', 'exp', 'jti', 'flywp_user_id' ] as $claim ) {
123	if ( ! array_key_exists( $claim, $claims ) ) {
124	return false;
125	}
126	}
127
128	if ( ! is_string( $claims['sub'] ) \|\| $claims['sub'] === '' ) {
129	return false;
130	}
131
132	if ( ! is_int( $claims['sid'] ) \|\| ! is_int( $claims['iat'] ) \|\| ! is_int( $claims['exp'] ) \|\| ! is_int( $claims['flywp_user_id'] ) ) {
133	return false;
134	}
135
136	return is_string( $claims['jti'] ) && preg_match( '/^[a-f0-9]{32}$/', $claims['jti'] ) === 1;
137	}
138
139	/**
140	* Whether the token is inside its stated lifetime, and that lifetime is plausible.
141	*
142	* @param array $claims Decoded claims.
143	* @param int $now Current unix timestamp.
144	* @param int $skew Clock drift to tolerate, in seconds.
145	*
146	* @return bool
147	*/
148	private static function is_fresh( array $claims, $now, $skew ) {
149	$lifetime = $claims['exp'] - $claims['iat'];
150
151	if ( $lifetime <= 0 \|\| $lifetime > self::MAX_LIFETIME ) {
152	return false;
153	}
154
155	if ( $now + $skew < $claims['iat'] ) {
156	return false;
157	}
158
159	return $now <= ( $claims['exp'] + $skew );
160	}
161
162	/**
163	* Decode base64url, rejecting anything outside the alphabet.
164	*
165	* @param string $value Encoded segment.
166	*
167	* @return string\|null Raw bytes, or null when the segment is not base64url.
168	*/
169	private static function base64url_decode( $value ) {
170	if ( ! is_string( $value ) \|\| preg_match( '/^[A-Za-z0-9\-_]+$/', $value ) !== 1 ) {
171	return null;
172	}
173
174	$padded = strtr( $value, '-_', '+/' );
175	$remainder = strlen( $padded ) % 4;
176
177	if ( $remainder !== 0 ) {
178	$padded .= str_repeat( '=', 4 - $remainder );
179	}
180
181	// phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode
182	$decoded = base64_decode( $padded, true );
183
184	return $decoded === false ? null : $decoded;
185	}
186	}
187