RSA_padding_check_none(3)

NAME

       RSA_padding_add_PKCS1_type_1, RSA_padding_check_PKCS1_type_1, RSA_pad-
       ding_add_PKCS1_type_2, RSA_padding_check_PKCS1_type_2, RSA_pad-
       ding_add_PKCS1_OAEP, RSA_padding_check_PKCS1_OAEP, RSA_pad-
       ding_add_SSLv23, RSA_padding_check_SSLv23, RSA_padding_add_none,
       RSA_padding_check_none - asymmetric encryption padding

SYNOPSIS

        #include <openssl/rsa.h>

        int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
           unsigned char *f, int fl);

        int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
           unsigned char *f, int fl, int rsa_len);

        int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,
           unsigned char *f, int fl);

        int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
           unsigned char *f, int fl, int rsa_len);

        int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
           unsigned char *f, int fl, unsigned char *p, int pl);

        int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
           unsigned char *f, int fl, int rsa_len, unsigned char *p, int pl);

        int RSA_padding_add_SSLv23(unsigned char *to, int tlen,
           unsigned char *f, int fl);

        int RSA_padding_check_SSLv23(unsigned char *to, int tlen,
           unsigned char *f, int fl, int rsa_len);

        int RSA_padding_add_none(unsigned char *to, int tlen,
           unsigned char *f, int fl);

        int RSA_padding_check_none(unsigned char *to, int tlen,
           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_pad-
       ding_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_pad-
       ding_add_xxx().

       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_PAD-
       DING: 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.

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 recov-
       ered data, -1 on error. Error codes can be obtained by calling
       ERR_get_error(3).

WARNING

       The RSA_padding_check_PKCS1_type_2() padding check leaks timing infor-
       mation 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. Otherwise it can be recommended to
       pass zero-padded f, so that fl equals to rsa_len, and if fixed by pro-
       tocol, tlen being set to the expected length. In such case leakage
       would be minimal, it would take attacker's ability to observe memory
       access pattern with byte granilarity as it occurs, post-factum timing
       analysis won't do.

SEE ALSO

       RSA_public_encrypt(3), RSA_private_decrypt(3), RSA_sign(3), RSA_ver-
       ify(3)

HISTORY

       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_SSLv23(), RSA_padding_check_SSLv23(), RSA_pad-
       ding_add_none() and RSA_padding_check_none() appeared in SSLeay 0.9.0.

       RSA_padding_add_PKCS1_OAEP() and RSA_padding_check_PKCS1_OAEP() were
       added in OpenSSL 0.9.2b.

1.0.2t                            2019-09-10   RSA_padding_add_PKCS1_type_1(3)