Provided by: libssl-doc_3.0.8-1ubuntu1_all 
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_none, RSA_padding_check_none -
asymmetric encryption padding
SYNOPSIS
#include <openssl/rsa.h>
The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely
by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):
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_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);
DESCRIPTION
All of the functions described on this page are deprecated. Applications should instead
use the EVP PKEY APIs.
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 RSA_NO_PADDING in order to implement OAEP with an encoding
parameter.
RSA_padding_add_xxx() encodes fl bytes from f so as to fit into tlen bytes and stores the
result at to. An error occurs if fl does not meet the size requirements of the encoding
method.
The following encoding methods are implemented:
PKCS1_type_1
PKCS #1 v2.0 EMSA-PKCS1-v1_5 (PKCS #1 v1.5 block type 1); used for signatures
PKCS1_type_2
PKCS #1 v2.0 EME-PKCS1-v1_5 (PKCS #1 v1.5 block type 2)
PKCS1_OAEP
PKCS #1 v2.0 EME-OAEP
none
simply copy the data
The random number generator must be seeded prior to calling RSA_padding_add_xxx(). If the
automatic seeding or reseeding of the OpenSSL CSPRNG fails due to external circumstances
(see RAND(7)), the operation will fail.
RSA_padding_check_xxx() verifies that the fl bytes at f contain a valid encoding for a
rsa_len byte RSA key in the respective encoding method and stores the recovered data of at
most tlen bytes (for RSA_NO_PADDING: of size tlen) at to.
For RSA_padding_xxx_OAEP(), p points to the encoding parameter of length pl. p may be NULL
if pl is 0.
For RSA_padding_xxx_OAEP_mgf1(), md points to the md hash, if md is NULL that means
md=sha1, and mgf1md points to the mgf1 hash, if mgf1md is NULL that means mgf1md=md.
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 ERR_get_error(3).
WARNINGS
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 RSA_NO_PADDING, 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.
SEE ALSO
RSA_public_encrypt(3), RSA_private_decrypt(3), RSA_sign(3), RSA_verify(3), RAND(7)
HISTORY
All of these functions were deprecated in OpenSSL 3.0.
COPYRIGHT
Copyright 2000-2021 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 <https://www.openssl.org/source/license.html>.