RSA_PADDING_ADD_PKCS1_TYPE_1(3)                       Library Functions Manual

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_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_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
     These 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_*() 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

     RSA_padding_check_*() 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_*_OAEP(), p points to the encoding parameter of length
     pl.  p may be NULL if pl is 0.

RETURN VALUES
     The RSA_padding_add_*() functions return 1 on success or 0 on error.  The
     RSA_padding_check_*() functions return the length of the recovered data
     or -1 on error.  Error codes can be obtained by calling ERR_get_error(3).

SEE ALSO
     RSA_new(3), RSA_private_decrypt(3), RSA_public_encrypt(3), RSA_sign(3),
     RSA_verify(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_none(), and RSA_padding_check_none() first appeared in
     SSLeay 0.9.0 and have been available since OpenBSD 2.4.

     RSA_padding_add_PKCS1_OAEP() and RSA_padding_check_PKCS1_OAEP() first
     appeared in OpenSSL 0.9.2b and have been available since OpenBSD 2.6.

BUGS
     The RSA_padding_check_PKCS1_type_2() padding check leaks timing
     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.

Linux 6.8.2-arch2-1             March 21, 2018             Linux 6.8.2-arch2-1