94 lines
2.6 KiB
Plaintext
94 lines
2.6 KiB
Plaintext
=pod
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=head1 NAME
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EVP_PKEY_decrypt_init, EVP_PKEY_decrypt - decrypt using a public key algorithm
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_PKEY_decrypt_init(EVP_PKEY_CTX *ctx);
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int EVP_PKEY_decrypt(EVP_PKEY_CTX *ctx,
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unsigned char *out, size_t *outlen,
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const unsigned char *in, size_t inlen);
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=head1 DESCRIPTION
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The EVP_PKEY_decrypt_init() function initializes a public key algorithm
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context using key B<pkey> for a decryption operation.
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The EVP_PKEY_decrypt() function performs a public key decryption operation
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using B<ctx>. The data to be decrypted is specified using the B<in> and
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B<inlen> parameters. If B<out> is B<NULL> then the maximum size of the output
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buffer is written to the B<outlen> parameter. If B<out> is not B<NULL> then
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before the call the B<outlen> parameter should contain the length of the
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B<out> buffer, if the call is successful the decrypted data is written to
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B<out> and the amount of data written to B<outlen>.
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=head1 NOTES
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After the call to EVP_PKEY_decrypt_init() algorithm specific control
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operations can be performed to set any appropriate parameters for the
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operation.
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The function EVP_PKEY_decrypt() can be called more than once on the same
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context if several operations are performed using the same parameters.
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=head1 RETURN VALUES
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EVP_PKEY_decrypt_init() and EVP_PKEY_decrypt() return 1 for success and 0
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or a negative value for failure. In particular a return value of -2
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indicates the operation is not supported by the public key algorithm.
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=head1 EXAMPLE
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Decrypt data using OAEP (for RSA keys):
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#include <openssl/evp.h>
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#include <openssl/rsa.h>
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EVP_PKEY_CTX *ctx;
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unsigned char *out, *in;
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size_t outlen, inlen;
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EVP_PKEY *key;
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/* NB: assumes key in, inlen are already set up
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* and that key is an RSA private key
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*/
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ctx = EVP_PKEY_CTX_new(key);
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if (!ctx)
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/* Error occurred */
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if (EVP_PKEY_decrypt_init(ctx) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_OAEP_PADDING) <= 0)
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/* Error */
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/* Determine buffer length */
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if (EVP_PKEY_decrypt(ctx, NULL, &outlen, in, inlen) <= 0)
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/* Error */
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out = OPENSSL_malloc(outlen);
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if (!out)
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/* malloc failure */
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if (EVP_PKEY_decrypt(ctx, out, &outlen, in, inlen) <= 0)
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/* Error */
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/* Decrypted data is outlen bytes written to buffer out */
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
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L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,
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L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
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L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>,
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L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>
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=head1 HISTORY
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These functions were first added to OpenSSL 1.0.0.
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=cut
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