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_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 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 genration to bits. 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 free
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 bits. If not specified 1024 is used.
The macro EVP_PKEY_CTX_set_dh_paramgen_prime_len() sets the length of
the DH prime parameter p 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.
