Updated: 2021/Apr/14


RSA_padding_add_PKCS1_type_1(3)     OpenSSL    RSA_padding_add_PKCS1_type_1(3)



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

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/rsa.h>

        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);

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 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

       SSLv23
           PKCS #1 EME-PKCS1-v1_5 with SSL-specific modification

       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)

COPYRIGHT
       Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.



1.1.1i                            2020-01-23   RSA_padding_add_PKCS1_type_1(3)