| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | RSA_private_encrypt, RSA_public_decrypt - low-level signature operations
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/rsa.h>
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| 10 |
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| 11 | int RSA_private_encrypt(int flen, unsigned char *from,
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| 12 | unsigned char *to, RSA *rsa, int padding);
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| 13 |
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| 14 | int RSA_public_decrypt(int flen, unsigned char *from,
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| 15 | unsigned char *to, RSA *rsa, int padding);
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| 16 |
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| 17 | =head1 DESCRIPTION
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| 18 |
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| 19 | These functions handle RSA signatures at a low-level.
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| 20 |
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| 21 | RSA_private_encrypt() signs the B<flen> bytes at B<from> (usually a
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| 22 | message digest with an algorithm identifier) using the private key
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| 23 | B<rsa> and stores the signature in B<to>. B<to> must point to
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| 24 | B<RSA_size(rsa)> bytes of memory.
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| 25 |
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| 26 | B<padding> denotes one of the following modes:
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| 27 |
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| 28 | =over 4
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| 29 |
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| 30 | =item RSA_PKCS1_PADDING
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| 31 |
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| 32 | PKCS #1 v1.5 padding. This function does not handle the
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| 33 | B<algorithmIdentifier> specified in PKCS #1. When generating or
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| 34 | verifying PKCS #1 signatures, L<RSA_sign(3)> and L<RSA_verify(3)> should be
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| 35 | used.
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| 36 |
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| 37 | =item RSA_NO_PADDING
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| 38 |
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| 39 | Raw RSA signature. This mode should I<only> be used to implement
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| 40 | cryptographically sound padding modes in the application code.
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| 41 | Signing user data directly with RSA is insecure.
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| 42 |
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| 43 | =back
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| 44 |
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| 45 | RSA_public_decrypt() recovers the message digest from the B<flen>
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| 46 | bytes long signature at B<from> using the signer's public key
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| 47 | B<rsa>. B<to> must point to a memory section large enough to hold the
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| 48 | message digest (which is smaller than B<RSA_size(rsa) -
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| 49 | 11>). B<padding> is the padding mode that was used to sign the data.
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| 50 |
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| 51 | =head1 RETURN VALUES
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| 52 |
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| 53 | RSA_private_encrypt() returns the size of the signature (i.e.,
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| 54 | RSA_size(rsa)). RSA_public_decrypt() returns the size of the
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| 55 | recovered message digest.
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| 56 |
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| 57 | On error, -1 is returned; the error codes can be
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| 58 | obtained by L<ERR_get_error(3)>.
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| 59 |
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| 60 | =head1 SEE ALSO
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| 61 |
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| 62 | L<ERR_get_error(3)>,
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| 63 | L<RSA_sign(3)>, L<RSA_verify(3)>
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| 64 |
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| 65 | =head1 COPYRIGHT
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| 66 |
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| 67 | Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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| 68 |
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| 69 | Licensed under the OpenSSL license (the "License"). You may not use
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| 70 | this file except in compliance with the License. You can obtain a copy
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| 71 | in the file LICENSE in the source distribution or at
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| 72 | L<https://www.openssl.org/source/license.html>.
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| 73 |
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| 74 | =cut
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