International PHP Conference Munich 2021

openssl_pkcs7_verify

(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)

openssl_pkcs7_verifyVerifies the signature of an S/MIME signed message

Description

openssl_pkcs7_verify(
    string $input_filename,
    int $flags,
    string|null $signers_certificates_filename = null,
    array $ca_info = [],
    string|null $untrusted_certificates_filename = null,
    string|null $content = null,
    string|null $output_filename = null
): bool|int

openssl_pkcs7_verify() reads the S/MIME message contained in the given file and examines the digital signature.

Parameters

input_filename

Path to the message.

flags

flags can be used to affect how the signature is verified - see PKCS7 constants for more information.

signers_certificates_filename

If the signers_certificates_filename is specified, it should be a string holding the name of a file into which the certificates of the persons that signed the messages will be stored in PEM format.

ca_info

If the ca_info is specified, it should hold information about the trusted CA certificates to use in the verification process - see certificate verification for more information about this parameter.

untrusted_certificates_filename

If the untrusted_certificates_filename is specified, it is the filename of a file containing a bunch of certificates to use as untrusted CAs.

content

You can specify a filename with content that will be filled with the verified data, but with the signature information stripped.

output_filename

Return Values

Returns true if the signature is verified, false if it is not correct (the message has been tampered with, or the signing certificate is invalid), or -1 on error.

Changelog

Version Description
8.0.0 signers_certificates_filename, untrusted_certificates_filename, content and output_filename are nullable now.
7.2.0 The output_filename parameter was added.

Notes

Note: As specified in RFC 2045, lines may not be longer than 76 characters in the input_filename parameter.

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User Contributed Notes 2 notes

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5
reg1barclay at REMOVETHIS dot live dot it
2 years ago
To verify a .p7m file with openssl_pkcs7_verify() you must convert it to S/MIME format. For example...
<?php
function der2smime($file)
{
   
$to=<<<TXT
MIME-Version: 1.0
Content-Disposition: attachment; filename="smime.p7m"
Content-Type: application/x-pkcs7-mime; smime-type=signed-data; name="smime.p7m"
Content-Transfer-Encoding: base64
\n
TXT;
   
$from=file_get_contents($file);
   
$to.=chunk_split(base64_encode($from));
    return
file_put_contents($file,$to);
}
?>
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-2
Krzychu
7 years ago
To read signed message in base64 (not encrypted with priv&pub key):

You can just decode content by "base64_decode" or "imap_base64" functions and then erase by hand(regexp) sign from bottom of mail. Unfortunately  in my case (mail from Outlook) that  message (decoded by "base64_decode") has some additional special chars in some places (ie. before every attachment encoded base_64) what make message e-mail unable to parse.

After couple of hours I solved this:
It's needed to save single e-mail and use 2x "openssl_pkcs7_verify" function in row on original email (with headers and content in base64 ):
  1st use - extract sign (certificate) from e-mail and save to file *.cert
  2nd use - extract (with use that *.cert file) decoded message to  file*.out

Code:
  $handle  =  imap_open('mailbox.eml', '', '');

  $msg = 'home/john/tmp/email1.eml';
  imap_savebody($handle, $msg,  1);

  openssl_pkcs7_verify($msg, 0, $msg . '.cert');
  openssl_pkcs7_verify($msg, 0, $msg . '.cert', array(), $msg . '.cert', $msg.'.out');

  $email_content = file_get_contents($msg . '.out');
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