5 RSA_padding_add_PKCS1_type_1, RSA_padding_check_PKCS1_type_1,
6 RSA_padding_add_PKCS1_type_2, RSA_padding_check_PKCS1_type_2,
7 RSA_padding_add_PKCS1_OAEP, RSA_padding_check_PKCS1_OAEP,
8 RSA_padding_add_PKCS1_OAEP_mgf1, RSA_padding_check_PKCS1_OAEP_mgf1,
9 RSA_padding_add_none, RSA_padding_check_none - asymmetric encryption
14 #include <openssl/rsa.h>
16 The following functions have been deprecated since OpenSSL 3.0, and can be
17 hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
18 see L<openssl_user_macros(7)>:
20 int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
21 const unsigned char *f, int fl);
23 int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
24 const unsigned char *f, int fl, int rsa_len);
26 int RSA_padding_add_PKCS1_type_2(unsigned char *to, int tlen,
27 const unsigned char *f, int fl);
29 int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
30 const unsigned char *f, int fl, int rsa_len);
32 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
33 const unsigned char *f, int fl,
34 const unsigned char *p, int pl);
36 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
37 const unsigned char *f, int fl, int rsa_len,
38 const unsigned char *p, int pl);
40 int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
41 const unsigned char *f, int fl,
42 const unsigned char *p, int pl,
43 const EVP_MD *md, const EVP_MD *mgf1md);
45 int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
46 const unsigned char *f, int fl, int rsa_len,
47 const unsigned char *p, int pl,
48 const EVP_MD *md, const EVP_MD *mgf1md);
50 int RSA_padding_add_none(unsigned char *to, int tlen,
51 const unsigned char *f, int fl);
53 int RSA_padding_check_none(unsigned char *to, int tlen,
54 const unsigned char *f, int fl, int rsa_len);
58 All of the functions described on this page are deprecated.
59 Applications should instead use the EVP PKEY APIs.
61 The RSA_padding_xxx_xxx() functions are called from the RSA encrypt,
62 decrypt, sign and verify functions. Normally they should not be called
63 from application programs.
65 However, they can also be called directly to implement padding for other
66 asymmetric ciphers. RSA_padding_add_PKCS1_OAEP() and
67 RSA_padding_check_PKCS1_OAEP() may be used in an application combined
68 with B<RSA_NO_PADDING> in order to implement OAEP with an encoding
71 RSA_padding_add_xxx() encodes B<fl> bytes from B<f> so as to fit into
72 B<tlen> bytes and stores the result at B<to>. An error occurs if B<fl>
73 does not meet the size requirements of the encoding method.
75 The following encoding methods are implemented:
81 PKCS #1 v2.0 EMSA-PKCS1-v1_5 (PKCS #1 v1.5 block type 1); used for signatures
85 PKCS #1 v2.0 EME-PKCS1-v1_5 (PKCS #1 v1.5 block type 2)
97 The random number generator must be seeded prior to calling
98 RSA_padding_add_xxx().
99 If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
100 external circumstances (see L<RAND(7)>), the operation will fail.
102 RSA_padding_check_xxx() verifies that the B<fl> bytes at B<f> contain
103 a valid encoding for a B<rsa_len> byte RSA key in the respective
104 encoding method and stores the recovered data of at most B<tlen> bytes
105 (for B<RSA_NO_PADDING>: of size B<tlen>)
108 For RSA_padding_xxx_OAEP(), B<p> points to the encoding parameter
109 of length B<pl>. B<p> may be B<NULL> if B<pl> is 0.
111 For RSA_padding_xxx_OAEP_mgf1(), B<md> points to the md hash,
112 if B<md> is B<NULL> that means md=sha1, and B<mgf1md> points to
113 the mgf1 hash, if B<mgf1md> is B<NULL> that means mgf1md=md.
117 The RSA_padding_add_xxx() functions return 1 on success, 0 on error.
118 The RSA_padding_check_xxx() functions return the length of the
119 recovered data, -1 on error. Error codes can be obtained by calling
124 The result of RSA_padding_check_PKCS1_type_2() is exactly the
125 information which is used to mount a classical Bleichenbacher
126 padding oracle attack. This is an inherent weakness in the PKCS #1
127 v1.5 padding design. Prefer PKCS1_OAEP padding. If that is not
128 possible, the result of RSA_padding_check_PKCS1_type_2() should be
129 checked in constant time if it matches the expected length of the
130 plaintext and additionally some application specific consistency
131 checks on the plaintext need to be performed in constant time.
132 If the plaintext is rejected it must be kept secret which of the
133 checks caused the application to reject the message.
134 Do not remove the zero-padding from the decrypted raw RSA data
135 which was computed by RSA_private_decrypt() with B<RSA_NO_PADDING>,
136 as this would create a small timing side channel which could be
137 used to mount a Bleichenbacher attack against any padding mode
138 including PKCS1_OAEP.
140 You should prefer the use of EVP PKEY APIs for PKCS#1 v1.5 decryption
141 as they implement the necessary workarounds internally.
145 L<RSA_public_encrypt(3)>,
146 L<RSA_private_decrypt(3)>,
147 L<RSA_sign(3)>, L<RSA_verify(3)>,
152 All of these functions were deprecated in OpenSSL 3.0.
156 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
158 Licensed under the Apache License 2.0 (the "License"). You may not use
159 this file except in compliance with the License. You can obtain a copy
160 in the file LICENSE in the source distribution or at
161 L<https://www.openssl.org/source/license.html>.