OpenSSL changes in PHP 5.6.x

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

ENTITY

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 ENTITY (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 ENTITY.

<?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);
?>

   

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 parameters 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 ENTITY, a new key pair will be created when using Diffie-Hellman parameters, thereby improving forward secrecy.

single_ecdh_use
If set to ENTITY, 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.

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());
?>

   

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');
?>

      

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;
?>

      

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);
?>