openssl_cms_decrypt

(PHP 8)

openssl_cms_decrypt — Decrypt a CMS message

Description

openssl_cms_decrypt(
    string $input_filename,
    string $output_filename,
    #[\SensitiveParameter] OpenSSLCertificate|string $certificate,
    #[\SensitiveParameter] OpenSSLAsymmetricKey|OpenSSLCertificate|array|string|null $private_key = null,
    int $encoding = OPENSSL_ENCODING_SMIME
): bool

Decrypts a CMS message.

Parameters

input_filename: The name of a file containing encrypted content.
output_filename: The name of the file to deposit the decrypted content.
certificate: The name of the file containing a certificate of the recipient.
private_key: The name of the file containing a PKCS#8 key.
encoding: The encoding of the input file. One of OPENSSL_ENCODING_SMIME, OPENSSL_ENCODING_DER or OPENSSL_ENCODING_PEM.

Return Values

Returns true on success or false on failure.

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User Contributed Notes 1 note

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Sebastian ¶

3 years ago

It took me a while to find out the correct way how to decrypt and verify data with these functions.
I needed that to communicate with German Health Insurance Providers as part of a DiGA. Maybe someone finds that useful.

<?php
function decryptAndVerify($signedAndEncryptedRawData): string
{
    $tempDir = __DIR__ . '/tmp';
    $originalFile = tempnam($tempDir, 'original');
    $decryptedFile = tempnam($tempDir, 'decrypted');
    $verifiedFile = tempnam($tempDir, 'verified');

    file_put_contents($originalFile, $signedAndEncryptedRawData);
    
    // One file with all possible certificates one after the other
    // -----BEGIN CERTIFICATE----- ...-----END CERTIFICATE-----
    $allPossibleSenderCertificates = __DIR__ . '/untrusted.pem';

    // Certificate:
    //    Data:
    //        Version: 3 (0x2)...
    $myCertificate = file_get_contents(__DIR__ . '/my.crt');
    $myPrivateKey = openssl_pkey_get_private(
    // -----BEGIN RSA PRIVATE KEY----- ... -----END RSA PRIVATE KEY-----
        file_get_contents(__DIR__ . '/my.prv.key.pem')
    );
    
    openssl_cms_decrypt(
        input_filename: $originalFile,
        output_filename: $decryptedFile,
        certificate: $myCertificate,
        private_key: $myPrivateKey,
        encoding: OPENSSL_ENCODING_DER
    );

    openssl_cms_verify(
        input_filename: $decryptedFile,
        flags: OPENSSL_CMS_BINARY | OPENSSL_CMS_NOSIGS | OPENSSL_CMS_NOVERIFY,
        ca_info: [],
        untrusted_certificates_filename: $allPossibleSenderCertificates,
        content: $verifiedFile,
        encoding: OPENSSL_ENCODING_DER
    );
    return file_get_contents($verifiedFile);
}

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