NAME
EVP_PKEY_CTX_ctrl,
EVP_PKEY_CTX_ctrl_str,
EVP_PKEY_CTX_set_signature_md,
EVP_PKEY_CTX_set_rsa_padding,
EVP_PKEY_CTX_set_rsa_pss_saltlen,
EVP_PKEY_CTX_set_rsa_rsa_keygen_bits,
EVP_PKEY_CTX_set_rsa_keygen_pubexp,
EVP_PKEY_CTX_set_dsa_paramgen_bits,
EVP_PKEY_CTX_set_dh_paramgen_prime_len,
EVP_PKEY_CTX_set_dh_paramgen_generator,
EVP_PKEY_CTX_set_ec_paramgen_curve_nid —
algorithm specific control
operations
SYNOPSIS
#include
<openssl/evp.h>
int
EVP_PKEY_CTX_ctrl(EVP_PKEY_CTX
*ctx, int keytype, int
optype, int cmd, int p1,
void *p2);
int
EVP_PKEY_CTX_ctrl_str(EVP_PKEY_CTX
*ctx, const char *type, const
char *value);
#include
<openssl/rsa.h>
int
EVP_PKEY_CTX_set_signature_md(EVP_PKEY_CTX
*ctx, const EVP_MD *md);
int
EVP_PKEY_CTX_set_rsa_padding(EVP_PKEY_CTX
*ctx, int pad);
int
EVP_PKEY_CTX_set_rsa_pss_saltlen(EVP_PKEY_CTX
*ctx, int len);
int
EVP_PKEY_CTX_set_rsa_rsa_keygen_bits(EVP_PKEY_CTX
*ctx, int mbits);
int
EVP_PKEY_CTX_set_rsa_keygen_pubexp(EVP_PKEY_CTX
*ctx, BIGNUM *pubexp);
#include
<openssl/dsa.h>
int
EVP_PKEY_CTX_set_dsa_paramgen_bits(EVP_PKEY_CTX
*ctx, int nbits);
#include
<openssl/dh.h>
int
EVP_PKEY_CTX_set_dh_paramgen_prime_len(EVP_PKEY_CTX
*ctx, int len);
int
EVP_PKEY_CTX_set_dh_paramgen_generator(EVP_PKEY_CTX
*ctx, int gen);
#include
<openssl/ec.h>
int
EVP_PKEY_CTX_set_ec_paramgen_curve_nid(EVP_PKEY_CTX
*ctx, int nid);
DESCRIPTION
The function
EVP_PKEY_CTX_ctrl()
sends a control operation to the context ctx. The key
type used must match keytype if it is not -1. The
parameter optype is a mask indicating which operations
the control can be applied to. The control command is indicated in
cmd and any additional arguments in
p1 and p2.
Applications will not normally call
EVP_PKEY_CTX_ctrl()
directly but will instead call one of the algorithm specific macros
below.
The function
EVP_PKEY_CTX_ctrl_str()
allows an application to send an algorithm specific control operation to a
context ctx in string form. This is intended to be
used for options specified on the command line or in text files. The
commands supported are documented in the
openssl(1) utility command line pages for the option
-pkeyopt which is supported by the
pkeyutl, genpkey, and
req commands.
All the remaining "functions" are implemented as macros.
The
EVP_PKEY_CTX_set_signature_md()
macro sets the message digest type used in a signature. It can be used with
any public key algorithm supporting signature operations.
The macro
EVP_PKEY_CTX_set_rsa_padding()
sets the RSA padding mode for ctx. The
pad parameter can take the value
RSA_PKCS1_PADDING for PKCS#1 padding,
RSA_SSLV23_PADDING for SSLv23 padding,
RSA_NO_PADDING for no padding,
RSA_PKCS1_OAEP_PADDING for OAEP padding (encrypt and
decrypt only), RSA_X931_PADDING for X9.31 padding
(signature operations only) and
RSA_PKCS1_PSS_PADDING (sign and verify only).
Two RSA padding modes behave
differently if
EVP_PKEY_CTX_set_signature_md()
is used. If this macro is called for PKCS#1 padding, the plaintext buffer is
an actual digest value and is encapsulated in a
DigestInfo structure according to PKCS#1 when signing
and this structure is expected (and stripped off) when verifying. If this
control is not used with RSA and PKCS#1 padding then the supplied data is
used directly and not encapsulated. In the case of X9.31 padding for RSA the
algorithm identifier byte is added or checked and removed if this control is
called. If it is not called then the first byte of the plaintext buffer is
expected to be the algorithm identifier byte.
The
EVP_PKEY_CTX_set_rsa_pss_saltlen()
macro sets the RSA PSS salt length to len. As its name
implies, it is only supported for PSS padding. Two special values are
supported: -1 sets the salt length to the digest length. When signing -2
sets the salt length to the maximum permissible value. When verifying -2
causes the salt length to be automatically determined based on the PSS block
structure. If this macro is not called a salt length value of -2 is used by
default.
The
EVP_PKEY_CTX_set_rsa_rsa_keygen_bits()
macro sets the RSA key length for RSA key generation to
mbits. If not specified, 1024 bits is used.
The
EVP_PKEY_CTX_set_rsa_keygen_pubexp()
macro sets the public exponent value for RSA key generation to
pubexp. Currently, it should be an odd integer. The
pubexp pointer is used internally by this function, so
it should not be modified or freed after the call. If this macro is not
called, then 65537 is used.
The macro
EVP_PKEY_CTX_set_dsa_paramgen_bits()
sets the number of bits used for DSA parameter generation to
nbits. If not specified, 1024 is used.
The macro
EVP_PKEY_CTX_set_dh_paramgen_prime_len()
sets the length of the DH prime parameter len for DH
parameter generation. If this macro is not called, then 1024 is used.
The
EVP_PKEY_CTX_set_dh_paramgen_generator()
macro sets DH generator to gen for DH parameter
generation. If not specified, 2 is used.
The
EVP_PKEY_CTX_set_ec_paramgen_curve_nid()
sets the EC curve for EC parameter generation to nid.
For EC parameter generation, this macro must be called or an error occurs
because there is no default curve.
RETURN VALUES
EVP_PKEY_CTX_ctrl() and its macros return
a positive value for success and 0 or a negative value for failure. In
particular, a return value of -2 indicates the operation is not supported by
the public key algorithm.
SEE ALSO
EVP_PKEY_CTX_new(3), EVP_PKEY_decrypt(3), EVP_PKEY_derive(3), EVP_PKEY_encrypt(3), EVP_PKEY_get_default_digest_nid(3), EVP_PKEY_keygen(3), EVP_PKEY_sign(3), EVP_PKEY_verify(3), EVP_PKEY_verify_recover(3)
HISTORY
These functions were first added to OpenSSL 1.0.0.