=pod =head1 NAME RSA_padding_add_PKCS1_type_1, RSA_padding_check_PKCS1_type_1, RSA_padding_add_PKCS1_type_2, RSA_padding_check_PKCS1_type_2, RSA_padding_add_PKCS1_OAEP, RSA_padding_check_PKCS1_OAEP, RSA_padding_add_PKCS1_OAEP_mgf1, RSA_padding_check_PKCS1_OAEP_mgf1, RSA_padding_add_SSLv23, RSA_padding_check_SSLv23, RSA_padding_add_none, RSA_padding_check_none - asymmetric encryption padding =head1 SYNOPSIS #include int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen, const unsigned char *f, int fl); int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen, const unsigned char *f, int fl, int rsa_len); int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen, const unsigned char *f, int fl); int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, const unsigned char *f, int fl, int rsa_len); int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen, const unsigned char *f, int fl, const unsigned char *p, int pl); int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen, const unsigned char *f, int fl, int rsa_len, const unsigned char *p, int pl); int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, const unsigned char *f, int fl, const unsigned char *p, int pl, const EVP_MD *md, const EVP_MD *mgf1md); int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, const unsigned char *f, int fl, int rsa_len, const unsigned char *p, int pl, const EVP_MD *md, const EVP_MD *mgf1md); int RSA_padding_add_SSLv23(unsigned char *to, int tlen, const unsigned char *f, int fl); int RSA_padding_check_SSLv23(unsigned char *to, int tlen, const unsigned char *f, int fl, int rsa_len); int RSA_padding_add_none(unsigned char *to, int tlen, const unsigned char *f, int fl); int RSA_padding_check_none(unsigned char *to, int tlen, const unsigned char *f, int fl, int rsa_len); =head1 DESCRIPTION The RSA_padding_xxx_xxx() functions are called from the RSA encrypt, decrypt, sign and verify functions. Normally they should not be called from application programs. However, they can also be called directly to implement padding for other asymmetric ciphers. RSA_padding_add_PKCS1_OAEP() and RSA_padding_check_PKCS1_OAEP() may be used in an application combined with B in order to implement OAEP with an encoding parameter. RSA_padding_add_xxx() encodes B bytes from B so as to fit into B bytes and stores the result at B. An error occurs if B does not meet the size requirements of the encoding method. The following encoding methods are implemented: =over 4 =item PKCS1_type_1 PKCS #1 v2.0 EMSA-PKCS1-v1_5 (PKCS #1 v1.5 block type 1); used for signatures =item PKCS1_type_2 PKCS #1 v2.0 EME-PKCS1-v1_5 (PKCS #1 v1.5 block type 2) =item PKCS1_OAEP PKCS #1 v2.0 EME-OAEP =item SSLv23 PKCS #1 EME-PKCS1-v1_5 with SSL-specific modification =item none simply copy the data =back The random number generator must be seeded prior to calling RSA_padding_add_xxx(). RSA_padding_check_xxx() verifies that the B bytes at B contain a valid encoding for a B byte RSA key in the respective encoding method and stores the recovered data of at most B bytes (for B: of size B) at B. For RSA_padding_xxx_OAEP(), B

points to the encoding parameter of length B. B

may be B if B is 0. For RSA_padding_xxx_OAEP_mgf1(), B points to the md hash, if B is B that means md=sha1, and B points to the mgf1 hash, if B is B that means mgf1md=md. =head1 RETURN VALUES The RSA_padding_add_xxx() functions return 1 on success, 0 on error. The RSA_padding_check_xxx() functions return the length of the recovered data, -1 on error. Error codes can be obtained by calling L. =head1 WARNING The result of RSA_padding_check_PKCS1_type_2() is a very sensitive information which can potentially be used to mount a Bleichenbacher padding oracle attack. This is an inherent weakness in the PKCS #1 v1.5 padding design. Prefer PKCS1_OAEP padding. If that is not possible, the result of RSA_padding_check_PKCS1_type_2() should be checked in constant time if it matches the expected length of the plaintext and additionally some application specific consistency checks on the plaintext need to be performed in constant time. If the plaintext is rejected it must be kept secret which of the checks caused the application to reject the message. Do not remove the zero-padding from the decrypted raw RSA data which was computed by RSA_private_decrypt() with B, as this would create a small timing side channel which could be used to mount a Bleichenbacher attack against any padding mode including PKCS1_OAEP. =head1 SEE ALSO L, L, L, L =head1 COPYRIGHT Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved. Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut