| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key algorithm
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/evp.h>
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| 10 |
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| 11 | int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
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| 12 | int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,
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| 13 | unsigned char *out, size_t *outlen,
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| 14 | const unsigned char *in, size_t inlen);
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| 15 |
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| 16 | =head1 DESCRIPTION
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| 17 |
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| 18 | The EVP_PKEY_decrypt_init() function initializes a public key algorithm
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| 19 | context using key B<pkey> for a decryption operation.
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| 20 |
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| 21 | The EVP_PKEY_decrypt() function performs a public key decryption operation
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| 22 | using B<ctx>. The data to be decrypted is specified using the B<in> and
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| 23 | B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output
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| 24 | buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then
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| 25 | before the call the B<outlen> parameter should contain the length of the
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| 26 | B<out> buffer, if the call is successful the decrypted data is written to
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| 27 | B<out> and the amount of data written to B<outlen>.
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| 28 |
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| 29 | =head1 NOTES
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| 30 |
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| 31 | After the call to EVP_PKEY_decrypt_init() algorithm specific control
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| 32 | operations can be performed to set any appropriate parameters for the
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| 33 | operation.
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| 34 |
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| 35 | The function EVP_PKEY_decrypt() can be called more than once on the same
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| 36 | context if several operations are performed using the same parameters.
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| 37 |
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| 38 | =head1 RETURN VALUES
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| 39 |
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| 40 | EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success and 0
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| 41 | or a negative value for failure. In particular a return value of -2
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| 42 | indicates the operation is not supported by the public key algorithm.
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| 43 |
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| 44 | =head1 EXAMPLES
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| 45 |
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| 46 | Decrypt data using OAEP (for RSA keys):
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| 47 |
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| 48 | #include <openssl/evp.h>
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| 49 | #include <openssl/rsa.h>
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| 50 |
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| 51 | EVP_PKEY_CTX *ctx;
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| 52 | ENGINE *eng;
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| 53 | unsigned char *out, *in;
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| 54 | size_t outlen, inlen;
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| 55 | EVP_PKEY *key;
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| 56 |
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| 57 | /*
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| 58 | * NB: assumes key, eng, in, inlen are already set up
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| 59 | * and that key is an RSA private key
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| 60 | */
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| 61 | ctx = EVP_PKEY_CTX_new(key, eng);
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| 62 | if (!ctx)
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| 63 | /* Error occurred */
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| 64 | if (EVP_PKEY_decrypt_init(ctx) <= 0)
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| 65 | /* Error */
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| 66 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0)
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| 67 | /* Error */
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| 68 |
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| 69 | /* Determine buffer length */
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| 70 | if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0)
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| 71 | /* Error */
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| 72 |
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| 73 | out = OPENSSL_malloc(outlen);
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| 74 |
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| 75 | if (!out)
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| 76 | /* malloc failure */
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| 77 |
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| 78 | if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0)
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| 79 | /* Error */
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| 80 |
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| 81 | /* Decrypted data is outlen bytes written to buffer out */
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| 82 |
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| 83 | =head1 SEE ALSO
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| 84 |
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| 85 | L<EVP_PKEY_CTX_new(3)>,
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| 86 | L<EVP_PKEY_encrypt(3)>,
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| 87 | L<EVP_PKEY_sign(3)>,
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| 88 | L<EVP_PKEY_verify(3)>,
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| 89 | L<EVP_PKEY_verify_recover(3)>,
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| 90 | L<EVP_PKEY_derive(3)>
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| 91 |
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| 92 | =head1 HISTORY
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| 93 |
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| 94 | These functions were added in OpenSSL 1.0.0.
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| 95 |
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| 96 | =head1 COPYRIGHT
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| 97 |
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| 98 | Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.
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| 99 |
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| 100 | Licensed under the OpenSSL license (the "License"). You may not use
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| 101 | this file except in compliance with the License. You can obtain a copy
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| 102 | in the file LICENSE in the source distribution or at
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| 103 | L<https://www.openssl.org/source/license.html>.
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| 104 |
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| 105 | =cut
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