| 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_init_ex,
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| 6 | EVP_PKEY_decrypt - decrypt using a public key algorithm
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| 7 |
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| 8 | =head1 SYNOPSIS
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| 9 |
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| 10 | #include <openssl/evp.h>
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| 11 |
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| 12 | int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
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| 13 | int EVP_PKEY_decrypt_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]);
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| 14 | int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,
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| 15 | unsigned char *out, size_t *outlen,
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| 16 | const unsigned char *in, size_t inlen);
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| 17 |
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| 18 | =head1 DESCRIPTION
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| 19 |
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| 20 | The EVP_PKEY_decrypt_init() function initializes a public key algorithm
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| 21 | context using key I<pkey> for a decryption operation.
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| 22 |
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| 23 | The EVP_PKEY_decrypt_init_ex() function initializes a public key algorithm
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| 24 | context using key I<pkey> for a decryption operation and sets the
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| 25 | algorithm specific I<params>.
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| 26 |
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| 27 | The EVP_PKEY_decrypt() function performs a public key decryption operation
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| 28 | using I<ctx>. The data to be decrypted is specified using the I<in> and
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| 29 | I<inlen> parameters. If I<out> is NULL then the minimum required size of
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| 30 | the output buffer is written to the I<*outlen> parameter.
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| 31 |
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| 32 | If I<out> is not NULL then before the call the I<*outlen> parameter must
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| 33 | contain the length of the I<out> buffer. If the call is successful the
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| 34 | decrypted data is written to I<out> and the amount of the decrypted data
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| 35 | written to I<*outlen>, otherwise an error is returned.
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| 36 |
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| 37 | =head1 NOTES
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| 38 |
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| 39 | After the call to EVP_PKEY_decrypt_init() algorithm specific control
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| 40 | operations can be performed to set any appropriate parameters for the
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| 41 | operation. These operations can be included in the EVP_PKEY_decrypt_init_ex()
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| 42 | call.
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| 43 |
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| 44 | The function EVP_PKEY_decrypt() can be called more than once on the same
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| 45 | context if several operations are performed using the same parameters.
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| 46 |
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| 47 | =head1 RETURN VALUES
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| 48 |
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| 49 | EVP_PKEY_decrypt_init(), EVP_PKEY_decrypt_init_ex() and EVP_PKEY_decrypt()
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| 50 | return 1 for success and 0 or a negative value for failure. In particular a
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| 51 | return value of -2 indicates the operation is not supported by the public key
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| 52 | algorithm.
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| 53 |
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| 54 | =head1 EXAMPLES
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| 55 |
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| 56 | Decrypt data using OAEP (for RSA keys):
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| 57 |
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| 58 | #include <openssl/evp.h>
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| 59 | #include <openssl/rsa.h>
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| 60 |
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| 61 | EVP_PKEY_CTX *ctx;
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| 62 | ENGINE *eng;
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| 63 | unsigned char *out, *in;
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| 64 | size_t outlen, inlen;
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| 65 | EVP_PKEY *key;
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| 66 |
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| 67 | /*
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| 68 | * NB: assumes key, eng, in, inlen are already set up
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| 69 | * and that key is an RSA private key
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| 70 | */
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| 71 | ctx = EVP_PKEY_CTX_new(key, eng);
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| 72 | if (!ctx)
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| 73 | /* Error occurred */
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| 74 | if (EVP_PKEY_decrypt_init(ctx) <= 0)
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| 75 | /* Error */
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| 76 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_OAEP_PADDING) <= 0)
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| 77 | /* Error */
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| 78 |
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| 79 | /* Determine buffer length */
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| 80 | if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0)
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| 81 | /* Error */
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| 82 |
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| 83 | out = OPENSSL_malloc(outlen);
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| 84 |
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| 85 | if (!out)
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| 86 | /* malloc failure */
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| 87 |
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| 88 | if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0)
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| 89 | /* Error */
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| 90 |
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| 91 | /* Decrypted data is outlen bytes written to buffer out */
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| 92 |
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| 93 | =head1 SEE ALSO
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| 94 |
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| 95 | L<EVP_PKEY_CTX_new(3)>,
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| 96 | L<EVP_PKEY_encrypt(3)>,
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| 97 | L<EVP_PKEY_sign(3)>,
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| 98 | L<EVP_PKEY_verify(3)>,
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| 99 | L<EVP_PKEY_verify_recover(3)>,
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| 100 | L<EVP_PKEY_derive(3)>
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| 101 |
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| 102 | =head1 HISTORY
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| 103 |
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| 104 | These functions were added in OpenSSL 1.0.0.
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| 105 |
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| 106 | =head1 COPYRIGHT
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| 107 |
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| 108 | Copyright 2006-2022 The OpenSSL Project Authors. All Rights Reserved.
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| 109 |
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| 110 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 111 | this file except in compliance with the License. You can obtain a copy
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| 112 | in the file LICENSE in the source distribution or at
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| 113 | L<https://www.openssl.org/source/license.html>.
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| 114 |
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| 115 | =cut
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