NAME

Crypt::OpenSSL::RSA - RSA encoding and decoding, using the openSSL libraries

SYNOPSIS

use Crypt::OpenSSL::Random;
use Crypt::OpenSSL::RSA;

# not necessary if we have /dev/random:
Crypt::OpenSSL::Random::random_seed($good_entropy);
Crypt::OpenSSL::RSA->import_random_seed();
$rsa_pub = Crypt::OpenSSL::RSA->new_public_key($key_string);
$ciphertext = $rsa->encrypt($plaintext);

$rsa_priv = Crypt::OpenSSL::RSA->new_private_key($key_string);
$plaintext = $rsa->decrypt($ciphertext);

$rsa = Crypt::OpenSSL::RSA->generate_key(1024); # or
$rsa = Crypt::OpenSSL::RSA->generate_key(1024, $prime);

print "private key is:\n", $rsa->get_private_key_string();
print "public key (in PKCS1 format) is:\n",
      $rsa->get_public_key_string();
print "public key (in X509 format) is:\n",
      $rsa->get_public_key_x509_string();

$rsa_priv->use_md5_hash(); # insecure. use_sha256_hash or use_sha1_hash are the default
$signature = $rsa_priv->sign($plaintext);
print "Signed correctly\n" if ($rsa->verify($plaintext, $signature));

SECURITY

Version 0.35 makes the use of PKCS#1 v1.5 padding a fatal error. It is very difficult to implement PKCS#1 v1.5 padding securely. If you are still using RSA in in general, you should be looking at alternative encryption algorithms. Version 0.36 implements RSA-PSS padding (PKCS#1 v2.1) and makes setting an invalid padding a fatal error. Note, PKCS1_OAEP can only be used for encryption and PKCS1_PSS can only be used for signing.

DESCRIPTION

Crypt::OpenSSL::RSA provides the ability to RSA encrypt strings which are somewhat shorter than the block size of a key. It also allows for decryption, signatures and signature verification.

NOTE: Many of the methods in this package can croak, so use eval, or Error.pm's try/catch mechanism to capture errors. Also, while some methods from earlier versions of this package return true on success, this (never documented) behavior is no longer the case.

Class Methods

• new_public_key

  Create a new Crypt::OpenSSL::RSA object by loading a public key in from a string containing Base64/DER-encoding of either the PKCS1 or X.509 representation of the key. The string should include the -----BEGIN...----- and -----END...----- lines.

  The padding is set to PKCS1_OAEP, but can be changed with the use_xxx_padding methods.

  Note, PKCS1_OAEP can only be used for encryption. You must specifically call use_pkcs1_pss_padding (or use_pkcs1_pss_padding) prior to signing operations.

• new_private_key

  Create a new Crypt::OpenSSL::RSA object by loading a private key in from an string containing the Base64/DER encoding of the PKCS1 representation of the key. The string should include the -----BEGIN...----- and -----END...----- lines. The padding is set to PKCS1_OAEP, but can be changed with use_xxx_padding.

  An optional parameter can be passed for passphase protected private key:

  • passphase

    The passphase which protects the private key.

• generate_key

  Create a new Crypt::OpenSSL::RSA object by constructing a private/public key pair. The first (mandatory) argument is the key size, while the second optional argument specifies the public exponent (the default public exponent is 65537). The padding is set to PKCS1_OAEP, but can be changed with use_xxx_padding methods.

• new_key_from_parameters

  Given Crypt::OpenSSL::Bignum objects for n, e, and optionally d, p, and q, where p and q are the prime factors of n, e is the public exponent and d is the private exponent, create a new Crypt::OpenSSL::RSA object using these values. If p and q are provided and d is undef, d is computed. Note that while p and q are not necessary for a private key, their presence will speed up computation.

• import_random_seed

  Import a random seed from Crypt::OpenSSL::Random, since the OpenSSL libraries won't allow sharing of random structures across perl XS modules.

Instance Methods

• DESTROY

  Clean up after ourselves. In particular, erase and free the memory occupied by the RSA key structure.

• get_public_key_string

  Return the Base64/DER-encoded PKCS1 representation of the public key. This string has header and footer lines:

    -----BEGIN RSA PUBLIC KEY------
    -----END RSA PUBLIC KEY------
  

• get_public_key_x509_string

  Return the Base64/DER-encoded representation of the "subject public key", suitable for use in X509 certificates. This string has header and footer lines:

    -----BEGIN PUBLIC KEY------
    -----END PUBLIC KEY------
  

  and is the format that is produced by running openssl rsa -pubout.

• get_private_key_string

  Return the Base64/DER-encoded PKCS1 representation of the private key. This string has header and footer lines:

    -----BEGIN RSA PRIVATE KEY------
    -----END RSA PRIVATE KEY------
  

  2 optional parameters can be passed for passphase protected private key string:

  • passphase

    The passphase which protects the private key.

  • cipher name

    The cipher algorithm used to protect the private key. Default to 'des3'.

• encrypt

  Encrypt a binary "string" using the public (portion of the) key.

• decrypt

  Decrypt a binary "string". Croaks if the key is public only.

• private_encrypt

  Encrypt a binary "string" using the private key. Croaks if the key is public only.

• public_decrypt

  Decrypt a binary "string" using the public (portion of the) key.

• sign

  Sign a string using the secret (portion of the) key.

• verify

  Check the signature on a text.

Padding Methods

Versions prior to 0.35 allowed using pkcs1 padding for both encryption and signature operations but has been disabled for security reasons.

While use_no_padding can be used for encryption or signature operations use_pkcs1_pss_padding is used for signature operations and use_pkcs1_oaep_padding is used for encryption operations.

Version 0.38 sets the appropriate padding for each operation unless use_no_padding is called before either operation.

Note: while "pkcs1-pss" is the effective replacement for "pkcs1" your use case may require some additional steps. JSON Web Tokens (JWT) for instance require the algorithm to be changed from "RS256" for "pkcs1" (SHA1256) to "PS256" for "pkcs1-pss" (SHA-256 and MGF1 with SHA-256)

• use_no_padding

  Use raw RSA encryption. This mode should only be used to implement cryptographically sound padding modes in the application code. Encrypting user data directly with RSA is insecure.

• use_pkcs1_padding

  PKCS #1 v1.5 padding has been disabled as it is nearly impossible to use this padding method in a secure manner. It is known to be vulnerable to timing based side channel attacks. use_pkcs1_padding() results in a fatal error.

  Marvin Attack

• use_pkcs1_oaep_padding

  Use EME-OAEP padding as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty encoding parameter. This mode of padding is recommended for all new applications. It is the default mode used by Crypt::OpenSSL::RSA but is only valid for encryption/decryption.

• use_pkcs1_pss_padding

  Use RSA-PSS padding as defined in PKCS#1 v2.1. In general, RSA-PSS should be used as a replacement for RSA-PKCS#1 v1.5. The module specifies the message digest being requested and the appropriate mgf1 setting and salt length for the digest.

  Note: RSA-PSS cannot be used for encryption/decryption and results in a fatal error. Call use_pkcs1_oaep_padding for encryption operations.

• use_sslv23_padding

  Use PKCS #1 v1.5 padding with an SSL-specific modification that denotes that the server is SSL3 capable.

  Not available since OpenSSL 3.

Hash/Digest Methods

• use_md5_hash

  Use the RFC 1321 MD5 hashing algorithm by Ron Rivest when signing and verifying messages.

  Note that this is considered insecure.

• use_sha1_hash

  Use the RFC 3174 Secure Hashing Algorithm (FIPS 180-1) when signing and verifying messages. This is the default, when use_sha256_hash is not available.

• use_sha224_hash, use_sha256_hash, use_sha384_hash, use_sha512_hash

  These FIPS 180-2 hash algorithms, for use when signing and verifying messages, are only available with newer openssl versions (>= 0.9.8).

  use_sha256_hash is the default hash mode when available.

• use_ripemd160_hash

  Dobbertin, Bosselaers and Preneel's RIPEMD hashing algorithm when signing and verifying messages.

• use_whirlpool_hash

  Vincent Rijmen und Paulo S. L. M. Barreto ISO/IEC 10118-3:2004 WHIRLPOOL hashing algorithm when signing and verifying messages.

• size

  Returns the size, in bytes, of the key. All encrypted text will be of this size, and depending on the padding mode used, the length of the text to be encrypted should be:

  • pkcs1_oaep_padding

    at most 42 bytes less than this size.

  • pkcs1_padding or sslv23_padding

    at most 11 bytes less than this size.

  • no_padding

    exactly this size.

• check_key

  This function validates the RSA key, returning a true value if the key is valid, and a false value otherwise. Croaks if the key is public only.

• get_key_parameters

  Return Crypt::OpenSSL::Bignum objects representing the values of n, e, d, p, q, d mod (p-1), d mod (q-1), and 1/q mod p, where p and q are the prime factors of n, e is the public exponent and d is the private exponent. Some of these values may return as undef; only n and e will be defined for a public key. The Crypt::OpenSSL::Bignum module must be installed for this to work.

• is_private

  Return true if this is a private key, and false if it is private only.

BUGS

There is a small memory leak when generating new keys of more than 512 bits.

AUTHOR

Ian Robertson, [email protected]. For support, please email [email protected].

ACKNOWLEDGEMENTS

LICENSE

Copyright (c) 2001-2011 Ian Robertson. Crypt::OpenSSL::RSA is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

perl(1), Crypt::OpenSSL::Random, Crypt::OpenSSL::Bignum, rsa(3), RSA_new(3), RSA_public_encrypt(3), RSA_size(3), RSA_generate_key(3), RSA_check_key(3)