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_none, RSA_padding_check_none - asymmetric encryption padding

SYNOPSIS
libcrypto
#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.