RSA_PKEY_CTX_CTRL(3)

NAME
RSA_pkey_ctx_ctrl, EVP_PKEY_CTX_set_rsa_padding, EVP_PKEY_CTX_get_rsa_padding, EVP_PKEY_CTX_set_rsa_keygen_bits, EVP_PKEY_CTX_set_rsa_keygen_pubexp, EVP_PKEY_CTX_set_rsa_mgf1_md, EVP_PKEY_CTX_get_rsa_mgf1_md, EVP_PKEY_CTX_set_rsa_oaep_md, EVP_PKEY_CTX_get_rsa_oaep_md, EVP_PKEY_CTX_set0_rsa_oaep_label, EVP_PKEY_CTX_get0_rsa_oaep_label, EVP_PKEY_CTX_set_rsa_pss_saltlen, EVP_PKEY_CTX_get_rsa_pss_saltlen, EVP_PKEY_CTX_set_rsa_pss_keygen_md, EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md, EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen - RSA private key control operations

SYNOPSIS
libcrypto
#include <openssl/rsa.h>
int
RSA_pkey_ctx_ctrl(EVP_PKEY_CTX *ctx, int optype, int cmd, int p1, void *p2);
int
EVP_PKEY_CTX_set_rsa_padding(EVP_PKEY_CTX *ctx, int pad);
int
EVP_PKEY_CTX_get_rsa_padding(EVP_PKEY_CTX *ctx, int *ppad);
int
EVP_PKEY_CTX_set_rsa_keygen_bits(EVP_PKEY_CTX *ctx, int mbits);
int
EVP_PKEY_CTX_set_rsa_keygen_pubexp(EVP_PKEY_CTX *ctx, BIGNUM *pubexp);
int
EVP_PKEY_CTX_set_rsa_mgf1_md(EVP_PKEY_CTX *ctx, const EVP_MD *md);
int
EVP_PKEY_CTX_get_rsa_mgf1_md(EVP_PKEY_CTX *ctx, const EVP_MD **pmd);
int
EVP_PKEY_CTX_set_rsa_oaep_md(EVP_PKEY_CTX *ctx, const EVP_MD *md);
int
EVP_PKEY_CTX_get_rsa_oaep_md(EVP_PKEY_CTX *ctx, const EVP_MD **pmd);
int
EVP_PKEY_CTX_set0_rsa_oaep_label(EVP_PKEY_CTX *ctx, unsigned char *label, int len);
int
EVP_PKEY_CTX_get0_rsa_oaep_label(EVP_PKEY_CTX *ctx, unsigned char **plabel);
int
EVP_PKEY_CTX_set_rsa_pss_saltlen(EVP_PKEY_CTX *ctx, int len);
int
EVP_PKEY_CTX_get_rsa_pss_saltlen(EVP_PKEY_CTX *ctx, int *plen);
int
EVP_PKEY_CTX_set_rsa_pss_keygen_md(EVP_PKEY_CTX *pctx, const EVP_MD *md);
int
EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md(EVP_PKEY_CTX *pctx, const EVP_MD *md);
int
EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen(EVP_PKEY_CTX *pctx, int saltlen);

DESCRIPTION
The function RSA_pkey_ctx_ctrl() is a shallow wrapper around EVP_PKEY_CTX_ctrl(3) which only succeeds if ctx matches either EVP_PKEY_RSA or EVP_PKEY_RSA_PSS.

All the remaining "functions" are implemented as macros.

The EVP_PKEY_CTX_set_rsa_padding() macro sets the RSA padding mode for ctx. The pad parameter can take the value RSA_PKCS1_PADDING for PKCS#1 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). Only the last one can be used with keys of the type EVP_PKEY_RSA_PSS.

Two RSA padding modes behave differently if EVP_PKEY_CTX_set_signature_md(3) 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_get_rsa_padding() macro retrieves the RSA padding mode for ctx.

The EVP_PKEY_CTX_set_rsa_keygen_bits() macro sets the RSA key length for RSA or RSA-PSS key generation to mbits. The smallest supported value is 512 bits. If not specified, 1024 bits is used.

The EVP_PKEY_CTX_set_rsa_keygen_pubexp() macro sets the public exponent value for RSA or RSA-PSS 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 EVP_PKEY_CTX_set_rsa_mgf1_md() macro sets the MGF1 digest for RSA padding schemes to md. Unless explicitly specified, the signing digest is used. The padding mode must have been set to RSA_PKCS1_OAEP_PADDING or RSA_PKCS1_PSS_PADDING. If the key is of the type EVP_PKEY_RSA_PSS and has usage restrictions, an error occurs if an attempt is made to set the digest to anything other than the restricted value.

The EVP_PKEY_CTX_get_rsa_mgf1_md() macro retrieves the MGF1 digest for ctx. Unless explicitly specified, the signing digest is used. The padding mode must have been set to RSA_PKCS1_OAEP_PADDING or RSA_PKCS1_PSS_PADDING.

  Optimal asymmetric encryption padding
The following macros require that the padding mode was set to RSA_PKCS1_OAEP_PADDING.

The EVP_PKEY_CTX_set_rsa_oaep_md() macro sets the message digest type used in RSA OAEP to md.

The EVP_PKEY_CTX_get_rsa_oaep_md() macro gets the message digest type used in RSA OAEP to *pmd.

The EVP_PKEY_CTX_set0_rsa_oaep_label() macro sets the RSA OAEP label to label and its length to len. If label is NULL or len is 0, the label is cleared. The library takes ownership of the label so the caller should not free the original memory pointed to by label.

The EVP_PKEY_CTX_get0_rsa_oaep_label() macro gets the RSA OAEP label to *plabel. The return value is the label length. The resulting pointer is owned by the library and should not be freed by the caller.

  Probabilistic signature scheme
The following macros require that the padding mode was set to RSA_PKCS1_PSS_PADDING.

The EVP_PKEY_CTX_set_rsa_pss_saltlen() macro sets the RSA PSS salt length to len. Three special values are supported: RSA_PSS_SALTLEN_DIGEST sets the salt length to the digest length. RSA_PSS_SALTLEN_MAX sets the salt length to the maximum permissible value. When signing, RSA_PSS_SALTLEN_AUTO sets the salt length to the maximum permissible value. When verifying, RSA_PSS_SALTLEN_AUTO 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 RSA_PSS_SALTLEN_AUTO is used by default.

If the key has usage restrictions and an attempt is made to set the salt length below the minimum value, an error occurs. Also, if the key has usage restrictions, RSA_PSS_SALTLEN_AUTO is not supported for verification.

The EVP_PKEY_CTX_get_rsa_pss_saltlen() macro retrieves the RSA PSS salt length for ctx.

Optional parameter restrictions can be specified when generating a PSS key. If any restrictions are set using the macros described below, then all parameters are restricted. For example, setting a minimum salt length also restricts the digest and MGF1 algorithms. If any restrictions are in place, then they are reflected in the corresponding parameters of the public key when (for example) a certificate request is signed.

EVP_PKEY_CTX_set_rsa_pss_keygen_md() restricts the digest algorithm the generated key can use to md.

EVP_PKEY_CTX_set_rsa_pss_keygen_mgf1_md() restricts the MGF1 algorithm the generated key can use to md.

EVP_PKEY_CTX_set_rsa_pss_keygen_saltlen() restricts the minimum salt length to saltlen.

RETURN VALUES
These functions return a positive value for success or 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_DigestInit(3), EVP_PKEY_CTX_ctrl(3), 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
The functions EVP_PKEY_CTX_set_rsa_padding(), EVP_PKEY_CTX_set_rsa_keygen_bits(), EVP_PKEY_CTX_set_rsa_keygen_pubexp(), and EVP_PKEY_CTX_set_rsa_pss_saltlen() first appeared in OpenSSL 1.0.0 and have been available since OpenBSD 4.9.

The functions EVP_PKEY_CTX_get_rsa_padding(), EVP_PKEY_CTX_set_rsa_mgf1_md(), EVP_PKEY_CTX_get_rsa_mgf1_md(), and EVP_PKEY_CTX_get_rsa_pss_saltlen() first appeared in OpenSSL 1.0.1 and have been available since OpenBSD 5.3.

The functions EVP_PKEY_CTX_set_rsa_oaep_md(), EVP_PKEY_CTX_get_rsa_oaep_md(), EVP_PKEY_CTX_set0_rsa_oaep_label(), and EVP_PKEY_CTX_get0_rsa_oaep_label() first appeared in OpenSSL 1.0.2 and have been available since OpenBSD 6.7.

The function RSA_pkey_ctx_ctrl() first appeared in OpenSSL 1.1.1 and has been available since OpenBSD 6.7.