This module uses the functions of OpenSSL for generation and verification
of signatures and for sealing (encrypting) and opening (decrypting)
data. OpenSSL offers many features that this module currently doesn't
support. Some of these may be added in the future.
In order to use the OpenSSL functions you need to install the OpenSSL package.
PHP between versions 4.0.5 and 4.3.1 will work with OpenSSL >= 0.9.5.
Other versions (PHP <=4.0.4pl1 and >= 4.3.2) require OpenSSL >=
0.9.6.
Warning
You are strongly encouraged to use the most recent OpenSSL version,
otherwise your web server could be vulnerable to attack.
To use PHP's OpenSSL support you must also compile PHP --with-openssl[=DIR].
Note to Win32 Users:
In order to enable this module on a Windows environment, you must copy
libeay32.dll from the DLL folder of the PHP/Win32 binary
package to the SYSTEM32 folder of your windows machine. (Ex:
C:\WINNT\SYSTEM32
or C:\WINDOWS\SYSTEM32)
Additionally, if you are planning to use the key generation and certificate
signing functions, you will need to install a valid openssl.cnf
on your system. As of PHP 4.3.0, we include a sample
configuration file in the openssl
folder of our win32 binary distribution. If you are using PHP 4.2.0 or
later and are missing the file, you can obtain it from
the OpenSSL home page or by
downloading the PHP 4.3.0 release and using the configuration file from
there.
Note to Win32 Users:
PHP will search for the openssl.cnf using the
following logic:
the OPENSSL_CONF environmental variable, if
set, will be used as the path (including filename) of the configuration
file.
the SSLEAY_CONF environmental variable, if
set, will be used as the path (including filename) of the configuration
file.
The file openssl.cnf will be assumed to be
found in the default certificate area, as configured at the time that
the openssl DLL was compiled. This is usually means that the default
filename is c:\usr\local\ssl\openssl.cnf.
In your installation, you need to decide whether to install the
configuration file at c:\usr\local\ssl\openssl.cnf or
whether to install it someplace else and use environmental variables
(possibly on a per-virtual-host basis) to locate the configuration file.
Note that it is possible to override the default path from the script using
the configargs of the functions that require a
configuration file.
Quite a few of the openssl functions require a key or a certificate
parameter. PHP 4.0.5 and earlier have to use a key or certificate
resource returned by one of the openssl_get_xxx functions.
Later versions may use one of the following methods:
A string having the format
file://path/to/file.pem - the named file must
contain a PEM encoded certificate/private key (it may contain both)
A string containing the content of a certificate/key, PEM encoded
For private keys, you may also use the syntax
array($key, $passphrase) where $key represents a
key specified using the file:// or textual content notation above, and
$passphrase represents a string containing the passphrase for that
private key
When calling a function that will verify a signature/certificate, the
cainfo parameter is an array containing file and
directory names that specify the locations of trusted CA files. If a
directory is specified, then it must be a correctly formed hashed
directory as the openssl command would use.
The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.
The S/MIME functions make use of flags which are specified using a
bitfield which can include one or more of the following values:
Table 1. PKCS7 CONSTANTS
Constant
Description
PKCS7_TEXT
Adds text/plain content type headers to encrypted/signed
message. If decrypting or verifying, it strips those headers from
the output - if the decrypted or verified message is not of MIME type
text/plain then an error will occur.
PKCS7_BINARY
Normally the input message is converted to "canonical" format
which is effectively using CR and LF as end of line: as required by
the S/MIME specification. When this options is present, no
translation occurs. This is useful when handling binary data which
may not be in MIME format.
PKCS7_NOINTERN
When verifying a message, certificates (if
any) included in the message are normally searched for the
signing certificate. With this option only the
certificates specified in the extracerts
parameter of openssl_pkcs7_verify() are
used. The supplied certificates can still be used as
untrusted CAs however.
PKCS7_NOVERIFY
Do not verify the signers certificate of a signed
message.
PKCS7_NOCHAIN
Do not chain verification of signers certificates: that is
don't use the certificates in the signed message as untrusted CAs.
PKCS7_NOCERTS
When signing a message the signer's certificate is normally
included - with this option it is excluded. This will reduce the
size of the signed message but the verifier must have a copy of the
signers certificate available locally (passed using the
extracerts to
openssl_pkcs7_verify() for example).
PKCS7_NOATTR
Normally when a message is signed, a set of attributes are
included which include the signing time and the supported symmetric
algorithms. With this option they are not included.
PKCS7_DETACHED
When signing a message, use cleartext signing with the MIME
type multipart/signed. This is the default
if you do not specify any flags to
openssl_pkcs7_sign().
If you turn this option off, the message will be signed using
opaque signing, which is more resistant to translation by mail relays
but cannot be read by mail agents that do not support S/MIME.
