man Crypt::SMIME (3): S/MIME message signing, verification, encryption and decryption

SYNOPSIS

use Crypt::SMIME;
my $plain = <<'EOF';
From: [email protected]
To: [email protected]
Subject: Crypt::SMIME test
This is a test mail. Please ignore...
EOF
my $smime = Crypt::SMIME->new();
$smime->setPrivateKey($privkey, $crt);
# $smime->setPublicKey([$icacert]); # if need be.
my $signed = $smime->sign($plain);
print $signed;

DESCRIPTION

This module provides a class for handling S/MIME messages. It can sign, verify, encrypt and decrypt messages. It requires libcrypto (<http://www.openssl.org>).

EXPORTS

No symbols are exported by default. The following symbols can optionally be exported:

"NO_CHECK_CERTIFICATE": See ``check()''.
"FORMAT_SMIME"
"FORMAT_ASN1"
"FORMAT_PEM": See ``extractCertificates()''.
":constants": Export all of the above.

METHODS

new()

  my $smime = Crypt::SMIME->new();

The constructor takes no arguments.

setPrivateKey()

  $smime->setPrivateKey($key, $crt);
  $smime->setPrivateKey($key, $crt, $password);

Store a private key and its X.509 certificate into the instance. The private key will be used for signing and decryption. Note that this method takes a PEM string, not a name of a file which contains a key or a certificate.

The private key and certificate must be encoded in PEM format. The method dies if it fails to load the key.

setPublicKey()

  $smime->setPublicKey($crt);
  $smime->setPublicKey([$crt1, $crt2, ...]);

Store one or more X.509 certificates into the instance. The public keys will be used for signing, verification and encryption.

The certificates must be encoded in PEM format. The method dies if it fails to load the certificates.

setPublicKeyStore()

  $smime->setPublicKeyStore($path, ...);

Set the paths of file or directory containing trusted certificates. The certificate stores will be used for verification.

The method dies if it fails to load the certificate stores.

sign()

  $signed_mime = $smime->sign($raw_mime);

Sign a MIME message and return an S/MIME message. The signature is always detached.

Any headers except "Content-*", "MIME-*" and "Subject" will be moved to the top-level of the MIME message. "Subject" header will be copied to both of the plain text part and the top-level for mail clients which can't properly handle S/MIME messages.

The resulting message will be tainted if any of the original MIME message, the private key or its certificate is tainted.

signonly()

  $sign = $smime->signonly($prepared_mime);

Generate a signature from a MIME message. The resulting signature is encoded in Base64. The MIME message to be passed to this method should be preprocessed beforehand by the prepareSmimeMessage() method. You would rarely need to call this method directly.

The resulting signature will be tainted if any of the original MIME message, the private key or its certificate is tainted.

prepareSmimeMessage()

  ($prepared_mime, $outer_header)
      = $smime->prepareSmimeMessage($source_mime);

Preprocess a MIME message to be signed. $prepared_mime will be a string containing the processed MIME message, and $outer_header will be a string that is a list of headers to be moved to the top-level of MIME message. You would rarely need to call this method directly.

The entity body of $source_mime will be directly copied to $prepared_mime. Any headers of $source_mime except "Content-*", "MIME-*" and "Subject" will be copied to $prepared_mime, and those excluded headers will be copied to $outer_header. Note that the "Subject" header will be copied to both side exceptionally.

check()

  use Crypt::SMIME qw(:constants);
  $source_mime = $smime->check($signed_mime);
  $source_mime = $smime->check($signed_mime, $flags);

Verify a signature of S/MIME message and return a MIME message. The method dies if it fails to verify it.

When the option "Crypt::SMIME::NO_CHECK_CERTIFICATE" is given as $flags, the signer's certificate chain is not verified. The default value for $flags is 0, which performs all the verifications.

The resulting message will be tainted if the original S/MIME message, the $flags, or at least one public key is tainted.

encrypt()

  $encrypted_mime = $smime->encrypt($raw_mime);

Encrypt a MIME message and return a S/MIME message.

The resulting message will be tainted if the original MIME message or at least one public key is tainted.

decrypt()

  $decrypted_mime = $smime->decrypt($encrypted_mime);

Decrypt an S/MIME and return a MIME message. This method dies if it fails to decrypt it.

The resulting message will be tainted if any of the original S/MIME message, the private key or its certificate is tainted.

isSigned()

  $is_signed = $smime->isSigned($mime);

Return true if the given string is a signed S/MIME message. Note that if the message was encrypted after signing, this method returns false because in that case the signature is hidden in the encrypted message.

isEncrypted()

  $is_encrypted = $smime->isEncrypted($mime);

Return true if the given string is an encrypted S/MIME message. Note that if the message was signed with non-detached signature after encryption, this method returns false because in that case the encrypted message is hidden in the signature.

FUNCTIONS

extractCertificates()

  use Crypt::SMIME qw(:constants);
  @certs = @{Crypt::SMIME::extractCertificates($data)};
  @certs = @{Crypt::SMIME::extractCertificates($data, FORMAT_SMIME)};

Get all X.509 certificates (and CRLs, if any) included in S/MIME message or PKCS#7 object $data. Optional $type parameter may specify type of data: "Crypt::SMIME::FORMAT_SMIME" (default) for S/MIME message; "Crypt::SMIME::FORMAT_ASN1" for binary format; "Crypt::SMIME::FORMAT_PEM" for PEM format.

getSigners()

  @certs = @{Crypt::SMIME::getSigners($data)};
  @certs = @{Crypt::SMIME::getSigners($data, $type)};

Get X.509 certificates of signers included in S/MIME message or PKCS#7 object. Optional $type parameter may specify type of data.

Note that any public keys returned by this function are not verified. check() should be executed to ensure public keys are valid.

AUTHOR

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself