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There was recently an instance where a user was confused by the deprecation warnings in the docs. They believed the warning applied to the immediately preceding function declarations, when it fact it applied to the following function declarations. https://mta.openssl.org/pipermail/openssl-users/2021-December/014665.html We clarify the wording to make it clear that the warning applies to the following functions. Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/17180)
118 lines
4.0 KiB
Plaintext
118 lines
4.0 KiB
Plaintext
=pod
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=head1 NAME
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RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography
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=head1 SYNOPSIS
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#include <openssl/rsa.h>
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The following functions have been deprecated since OpenSSL 3.0, and can be
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hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
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see L<openssl_user_macros(7)>:
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int RSA_public_encrypt(int flen, const unsigned char *from,
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unsigned char *to, RSA *rsa, int padding);
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int RSA_private_decrypt(int flen, const unsigned char *from,
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unsigned char *to, RSA *rsa, int padding);
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=head1 DESCRIPTION
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Both of the functions described on this page are deprecated.
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Applications should instead use L<EVP_PKEY_encrypt_init_ex(3)>,
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L<EVP_PKEY_encrypt(3)>, L<EVP_PKEY_decrypt_init_ex(3)> and
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L<EVP_PKEY_decrypt(3)>.
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RSA_public_encrypt() encrypts the B<flen> bytes at B<from> (usually a
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session key) using the public key B<rsa> and stores the ciphertext in
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B<to>. B<to> must point to RSA_size(B<rsa>) bytes of memory.
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B<padding> denotes one of the following modes:
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=over 4
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=item RSA_PKCS1_PADDING
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PKCS #1 v1.5 padding. This currently is the most widely used mode.
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However, it is highly recommended to use RSA_PKCS1_OAEP_PADDING in
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new applications. SEE WARNING BELOW.
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=item RSA_PKCS1_OAEP_PADDING
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EME-OAEP as defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty
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encoding parameter. This mode is recommended for all new applications.
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=item RSA_NO_PADDING
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Raw RSA encryption. This mode should I<only> be used to implement
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cryptographically sound padding modes in the application code.
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Encrypting user data directly with RSA is insecure.
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=back
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B<flen> must not be more than RSA_size(B<rsa>) - 11 for the PKCS #1 v1.5
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based padding modes, not more than RSA_size(B<rsa>) - 42 for
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RSA_PKCS1_OAEP_PADDING and exactly RSA_size(B<rsa>) for RSA_NO_PADDING.
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When a padding mode other than RSA_NO_PADDING is in use, then
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RSA_public_encrypt() will include some random bytes into the ciphertext
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and therefore the ciphertext will be different each time, even if the
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plaintext and the public key are exactly identical.
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The returned ciphertext in B<to> will always be zero padded to exactly
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RSA_size(B<rsa>) bytes.
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B<to> and B<from> may overlap.
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RSA_private_decrypt() decrypts the B<flen> bytes at B<from> using the
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private key B<rsa> and stores the plaintext in B<to>. B<flen> should
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be equal to RSA_size(B<rsa>) but may be smaller, when leading zero
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bytes are in the ciphertext. Those are not important and may be removed,
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but RSA_public_encrypt() does not do that. B<to> must point
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to a memory section large enough to hold the maximal possible decrypted
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data (which is equal to RSA_size(B<rsa>) for RSA_NO_PADDING,
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RSA_size(B<rsa>) - 11 for the PKCS #1 v1.5 based padding modes and
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RSA_size(B<rsa>) - 42 for RSA_PKCS1_OAEP_PADDING).
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B<padding> is the padding mode that was used to encrypt the data.
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B<to> and B<from> may overlap.
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=head1 RETURN VALUES
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RSA_public_encrypt() returns the size of the encrypted data (i.e.,
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RSA_size(B<rsa>)). RSA_private_decrypt() returns the size of the
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recovered plaintext. A return value of 0 is not an error and
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means only that the plaintext was empty.
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On error, -1 is returned; the error codes can be
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obtained by L<ERR_get_error(3)>.
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=head1 WARNINGS
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Decryption failures in the RSA_PKCS1_PADDING mode leak information
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which can potentially be used to mount a Bleichenbacher padding oracle
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attack. This is an inherent weakness in the PKCS #1 v1.5 padding
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design. Prefer RSA_PKCS1_OAEP_PADDING.
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=head1 CONFORMING TO
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SSL, PKCS #1 v2.0
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=head1 SEE ALSO
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L<ERR_get_error(3)>, L<RAND_bytes(3)>,
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L<RSA_size(3)>
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=head1 HISTORY
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Both of these functions were deprecated in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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