PHP: OpenSSL changes in PHP 5.6.x

OpenSSL changes in PHP 5.6.x

Stream wrappers now verify peer certificates and host names by default when using SSL/TLS

All encrypted client streams now enable peer verification by default. By default, this will use OpenSSL's default CA bundle to verify the peer certificate. In most cases, no changes will need to be made to communicate with servers with valid SSL certificates, as distributors generally configure OpenSSL to use known good CA bundles.

The default CA bundle may be overridden on a global basis by setting either the openssl.cafile or openssl.capath configuration setting, or on a per request basis by using the cafile or capath context options.

While not recommended in general, it is possible to disable peer certificate verification for a request by setting the verify_peer context option to false, and to disable peer name validation by setting the verify_peer_name context option to false.

Certificate fingerprints

Support has been added for extracting and verifying certificate fingerprints. openssl_x509_fingerprint() has been added to extract a fingerprint from an X.509 certificate, and two SSL stream context options have been added: capture_peer_cert to capture the peer's X.509 certificate, and peer_fingerprint to assert that the peer's certificate should match the given fingerprint.

Default ciphers updated

The default ciphers used by PHP have been updated to a more secure list based on the » Mozilla cipher recommendations, with two additional exclusions: anonymous Diffie-Hellman ciphers, and RC4.

This list can be accessed via the new OPENSSL_DEFAULT_STREAM_CIPHERS constant, and can be overridden (as in previous PHP versions) by setting the ciphers context option.

Compression disabled by default

SSL/TLS compression has been disabled by default to mitigate the CRIME attack. PHP 5.4.13 added a disable_compression context option to allow compression to be disabled: this is now set to true (that is, compression is disabled) by default.

Allow servers to prefer their cipher order

The honor_cipher_order SSL context option has been added to allow encrypted stream servers to mitigate BEAST vulnerabilities by preferring the server's ciphers to the client's.

Access the negotiated protocol and cipher

The protocol and cipher that were negotiated for an encrypted stream can now be accessed via stream_get_meta_data() or stream_context_get_options() when the capture_session_meta SSL context option is set to true.

<?php
$ctx = stream_context_create(['ssl' => [
    'capture_session_meta' => TRUE
]]);
 
$html = file_get_contents('https://google.com/', FALSE, $ctx);
$meta = stream_context_get_options($ctx)['ssl']['session_meta'];
var_dump($meta);
?>

The above example will output:

array(4) {
  ["protocol"]=>
  string(5) "TLSv1"
  ["cipher_name"]=>
  string(20) "ECDHE-RSA-AES128-SHA"
  ["cipher_bits"]=>
  int(128)
  ["cipher_version"]=>
  string(11) "TLSv1/SSLv3"
}

New options for perfect forward secrecy in encrypted stream servers

Encrypted client streams already support perfect forward secrecy, as it is generally controlled by the server. PHP encrypted server streams using certificates capable of perfect forward secrecy do not need to take any additional action to enable PFS; however a number of new SSL context options have been added to allow more control over PFS and deal with any compatibility issues that may arise.

ecdh_curve

This option allows the selection of a specific curve for use with ECDH ciphers. If not specified, prime256v1 will be used.

dh_param

A path to a file containing parametrs for Diffie-Hellman key exchange, such as that created by the following command:

openssl dhparam -out /path/to/my/certs/dh-2048.pem 2048

single_dh_use

If set to true, a new key pair will be created when using Diffie-Hellman parameters, thereby improving forward secrecy.

single_ecdh_use

If set to true, a new key pair will always be generated when ECDH cipher suites are negotiated. This improves forward secrecy.

SSL/TLS version selection

It is now possible to select specific versions of SSL and TLS via the crypto_method SSL context option or by specifying a specific transport when creating a stream wrapper (for example, by calling stream_socket_client() or stream_socket_server()).

The crypto_method SSL context option accepts a bitmask enumerating the protocols that are permitted, as does the crypto_type of stream_socket_enable_crypto().

**Selected protocol versions and corresponding options**
Protocol(s)	Client flag	Server flag	Transport
Any TLS or SSL version	`STREAM_CRYPTO_METHOD_ANY_CLIENT`	`STREAM_CRYPTO_METHOD_ANY_SERVER`	`ssl://`
Any TLS version	`STREAM_CRYPTO_METHOD_TLS_CLIENT`	`STREAM_CRYPTO_METHOD_TLS_SERVER`	`tls://`
TLS 1.0	`STREAM_CRYPTO_METHOD_TLSv1_0_CLIENT`	`STREAM_CRYPTO_METHOD_TLSv1_0_SERVER`	`tlsv1.0://`
TLS 1.1	`STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT`	`STREAM_CRYPTO_METHOD_TLSv1_1_SERVER`	`tlsv1.1://`
TLS 1.2	`STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT`	`STREAM_CRYPTO_METHOD_TLSv1_2_SERVER`	`tlsv1.2://`
SSL 3	`STREAM_CRYPTO_METHOD_SSLv3_CLIENT`	`STREAM_CRYPTO_METHOD_SSLv3_SERVER`	`sslv3://`

<?php

// Requiring TLS 1.0 or better when using file_get_contents():
$ctx = stream_context_create([
    'ssl' => [
        'crypto_method' => STREAM_CRYPTO_METHOD_TLS_CLIENT,
    ],
]);
$html = file_get_contents('https://google.com/', false, $ctx);

// Requiring TLS 1.1 or 1.2:
$ctx = stream_context_create([
    'ssl' => [
        'crypto_method' => STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT |
                           STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT,
    ],
]);
$html = file_get_contents('https://google.com/', false, $ctx);

// Connecting using the tlsv1.2:// stream socket transport.
$sock = stream_socket_client('tlsv1.2://google.com:443/');

?>

openssl_get_cert_locations() added

The openssl_get_cert_locations() function has been added: it returns the default locations PHP will search when looking for CA bundles.

<?php
var_dump(openssl_get_cert_locations());
?>

The above example will output:

array(8) {
  ["default_cert_file"]=>
  string(21) "/etc/pki/tls/cert.pem"
  ["default_cert_file_env"]=>
  string(13) "SSL_CERT_FILE"
  ["default_cert_dir"]=>
  string(18) "/etc/pki/tls/certs"
  ["default_cert_dir_env"]=>
  string(12) "SSL_CERT_DIR"
  ["default_private_dir"]=>
  string(20) "/etc/pki/tls/private"
  ["default_default_cert_area"]=>
  string(12) "/etc/pki/tls"
  ["ini_cafile"]=>
  string(0) ""
  ["ini_capath"]=>
  string(0) ""
}

SPKI support

Support has been added for generating, extracting and verifying signed public key and challenges (SPKAC). openssl_spki_new(), openssl_spki_verify(), openssl_spki_export_challenge(), and openssl_spki_export() have been added to create, verify export PEM public key and associated challenge from SPKAC's generated from a KeyGen HTML5 element.

openssl_spki_new

Generates a new SPKAC using private key, challenge string and hashing algorithm.

<?php
$pkey = openssl_pkey_new();
openssl_pkey_export($pkey, 'secret passphrase');

$spkac = openssl_spki_new($pkey, 'challenge string');
?>

The above example will output:

SPKAC=MIIBXjCByDCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEA3L0IfUijj7+A8CPC8EmhcdNoe5fUAog7OrBdhn7EkxFButUp40P7+LiYiygYG1TmoI/a5EgsLU3s9twEz3hmgY9mYIqb/rb+SF8qlD/K6KVyUORC7Wlz1Df4L8O3DuRGzx6/+3jIW6cPBpfgH1sVuYS1vDBsP/gMMIxwTsKJ4P0CAwEAARYkYjViMzYxMTktNjY5YS00ZDljLWEyYzctMGZjNGFhMjVlMmE2MA0GCSqGSIb3DQEBAwUAA4GBAF7hu0ifzmjonhAak2FhhBRsKFDzXdKIkrWxVNe8e0bZzMrWOxFM/rqBgeH3/gtOUDRS5Fnzyq425UsTYbjfiKzxGeCYCQJb1KJ2V5Ij/mIJHZr53WYEXHQTNMGR8RPm7IxwVXVSHIgAfXsXZ9IXNbFbcaLRiSTr9/N4U+MXUWL7

openssl_spki_verify

Verifies provided SPKAC.

<?php
$pkey = openssl_pkey_new();
openssl_pkey_export($pkey, 'secret passphrase');

$spkac = openssl_spki_new($pkey, 'challenge string');
var_dump(openssl_spki_verify($spkac));
?>

openssl_spki_export_challenge

Exports associated challenge from provided SPKAC.

<?php
$pkey = openssl_pkey_new();
openssl_pkey_export($pkey, 'secret passphrase');

$spkac = openssl_spki_new($pkey, 'challenge string');
$challenge = openssl_spki_export_challenge($spkac);
echo $challenge;
?>

The above example will output:

challenge string

openssl_spki_export

Exports the PEM formatted RSA public key from SPKAC.

<?php
$pkey = openssl_pkey_new();
openssl_pkey_export($pkey, 'secret passphrase');

$spkac = openssl_spki_new($pkey, 'challenge string');
echo openssl_spki_export($spkac);
?>

The above example will output:

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