doc/man3/EVP_DigestSignInit.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 EVP_DigestSignInit_ex, EVP_DigestSignInit, EVP_DigestSignUpdate,
 EVP_DigestSignFinal, EVP_DigestSign - EVP signing functions

 =head1 SYNOPSIS

  #include <openssl/evp.h>

  int EVP_DigestSignInit_ex(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
                            const char *mdname, OSSL_LIB_CTX *libctx,
                            const char *props, EVP_PKEY *pkey,
                            const OSSL_PARAM params[]);
  int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
                         const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
  int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
  int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);

  int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret,
                     size_t *siglen, const unsigned char *tbs,
                     size_t tbslen);

 =head1 DESCRIPTION

 The EVP signature routines are a high-level interface to digital signatures.
 Input data is digested first before the signing takes place.

 EVP_DigestSignInit_ex() sets up signing context I<ctx> to use a digest
 with the name I<mdname> and private key I<pkey>. The name of the digest to be
 used is passed to the provider of the signature algorithm in use. How that
 provider interprets the digest name is provider specific. The provider may
 implement that digest directly itself or it may (optionally) choose to fetch it
 (which could result in a digest from a different provider being selected). If the
 provider supports fetching the digest then it may use the I<props> argument for
 the properties to be used during the fetch. Finally, the passed parameters
 I<params>, if not NULL, are set on the context before returning.

 The I<pkey> algorithm is used to fetch a B<EVP_SIGNATURE> method implicitly, to
 be used for the actual signing. See L<provider(7)/Implicit fetch> for
 more information about implicit fetches.

 The OpenSSL default and legacy providers support fetching digests and can fetch
 those digests from any available provider. The OpenSSL fips provider also
 supports fetching digests but will only fetch digests that are themselves
 implemented inside the fips provider.

 I<ctx> must be created with EVP_MD_CTX_new() before calling this function. If
 I<pctx> is not NULL, the EVP_PKEY_CTX of the signing operation will be written
 to I<*pctx>: this can be used to set alternative signing options. Note that any
 existing value in I<*pctx> is overwritten. The EVP_PKEY_CTX value returned must
 not be freed directly by the application if I<ctx> is not assigned an
 EVP_PKEY_CTX value before being passed to EVP_DigestSignInit_ex()
 (which means the EVP_PKEY_CTX is created inside EVP_DigestSignInit_ex()
 and it will be freed automatically when the EVP_MD_CTX is freed). If the
 EVP_PKEY_CTX to be used is created by EVP_DigestSignInit_ex then it
 will use the B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
 specified in I<props>.

 The digest I<mdname> may be NULL if the signing algorithm supports it. The
 I<props> argument can always be NULL.

 No B<EVP_PKEY_CTX> will be created by EVP_DigestSignInit_ex() if the
 passed I<ctx> has already been assigned one via L<EVP_MD_CTX_set_pkey_ctx(3)>.
 See also L<SM2(7)>.

 Only EVP_PKEY types that support signing can be used with these functions. This
 includes MAC algorithms where the MAC generation is considered as a form of
 "signing". Built-in EVP_PKEY types supported by these functions are CMAC,
 Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.

 Not all digests can be used for all key types. The following combinations apply.

 =over 4

 =item DSA

 Supports SHA1, SHA224, SHA256, SHA384 and SHA512

 =item ECDSA

 Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3

 =item RSA with no padding

 Supports no digests (the digest I<type> must be NULL)

 =item RSA with X931 padding

 Supports SHA1, SHA256, SHA384 and SHA512

 =item All other RSA padding types

 Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
 SHA3-224, SHA3-256, SHA3-384, SHA3-512

 =item Ed25519 and Ed448

 Support no digests (the digest I<type> must be NULL)

 =item HMAC

 Supports any digest

 =item CMAC, Poly1305 and SipHash

 Will ignore any digest provided.

 =back

 If RSA-PSS is used and restrictions apply then the digest must match.

 EVP_DigestSignInit() works in the same way as EVP_DigestSignInit_ex()
 except that the I<mdname> parameter will be inferred from the supplied
 digest I<type>, and I<props> will be NULL. Where supplied the ENGINE I<e> will
 be used for the signing and digest algorithm implementations. I<e> may be NULL.

 EVP_DigestSignUpdate() hashes I<cnt> bytes of data at I<d> into the
 signature context I<ctx>. This function can be called several times on the
 same I<ctx> to include additional data.

 Unless I<sig> is NULL EVP_DigestSignFinal() signs the data in I<ctx>
 and places the signature in I<sig>.
 Otherwise the maximum necessary size of the output buffer is written to
 the I<siglen> parameter. If I<sig> is not NULL then before the call the
 I<siglen> parameter should contain the length of the I<sig> buffer. If the
 call is successful the signature is written to I<sig> and the amount of data
 written to I<siglen>.

 EVP_DigestSign() signs I<tbslen> bytes of data at I<tbs> and places the
 signature in I<sig> and its length in I<siglen> in a similar way to
 EVP_DigestSignFinal(). In the event of a failure EVP_DigestSign() cannot be
 called again without reinitialising the EVP_MD_CTX. If I<sig> is NULL before the
 call then I<siglen> will be populated with the required size for the I<sig>
 buffer. If I<sig> is non-NULL before the call then I<siglen> should contain the
 length of the I<sig> buffer.

 =head1 RETURN VALUES

 EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignFinal() and
 EVP_DigestSign() return 1 for success and 0 for failure.

 The error codes can be obtained from L<ERR_get_error(3)>.

 =head1 NOTES

 The B<EVP> interface to digital signatures should almost always be used in
 preference to the low-level interfaces. This is because the code then becomes
 transparent to the algorithm used and much more flexible.

 EVP_DigestSign() is a one shot operation which signs a single block of data
 in one function. For algorithms that support streaming it is equivalent to
 calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which
 do not support streaming (e.g. PureEdDSA) it is the only way to sign data.

 In previous versions of OpenSSL there was a link between message digest types
 and public key algorithms. This meant that "clone" digests such as EVP_dss1()
 needed to be used to sign using SHA1 and DSA. This is no longer necessary and
 the use of clone digest is now discouraged.

 For some key types and parameters the random number generator must be seeded.
 If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
 external circumstances (see L<RAND(7)>), the operation will fail.

 The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
 context. This means that calls to EVP_DigestSignUpdate() and
 EVP_DigestSignFinal() can be called later to digest and sign additional data.

 EVP_DigestSignInit() and EVP_DigestSignInit_ex() functions can be called
 multiple times on a context and the parameters set by previous calls should be
 preserved if the I<pkey> parameter is NULL. The call then just resets the state
 of the I<ctx>.

 The use of EVP_PKEY_get_size() with these functions is discouraged because some
 signature operations may have a signature length which depends on the
 parameters set. As a result EVP_PKEY_get_size() would have to return a value
 which indicates the maximum possible signature for any set of parameters.

 =head1 SEE ALSO

 L<EVP_DigestVerifyInit(3)>,
 L<EVP_DigestInit(3)>,
 L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
 L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
 L<SHA1(3)>, L<openssl-dgst(1)>,
 L<RAND(7)>

 =head1 HISTORY

 EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
 were added in OpenSSL 1.0.0.

 EVP_DigestSignInit_ex() was added in OpenSSL 3.0.

 EVP_DigestSignUpdate() was converted from a macro to a function in OpenSSL 3.0.

 =head1 COPYRIGHT

 Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.

 Licensed under the Apache License 2.0 (the "License").  You may not use
 this file except in compliance with the License.  You can obtain a copy
 in the file LICENSE in the source distribution or at
 L<https://www.openssl.org/source/license.html>.

 =cut
	=pod

	=head1 NAME

	EVP_DigestSignInit_ex, EVP_DigestSignInit, EVP_DigestSignUpdate,
	EVP_DigestSignFinal, EVP_DigestSign - EVP signing functions

	=head1 SYNOPSIS

	#include <openssl/evp.h>

	int EVP_DigestSignInit_ex(EVP_MD_CTX ctx, EVP_PKEY_CTX *pctx,
	const char mdname, OSSL_LIB_CTX libctx,
	const char props, EVP_PKEY pkey,
	const OSSL_PARAM params[]);
	int EVP_DigestSignInit(EVP_MD_CTX ctx, EVP_PKEY_CTX *pctx,
	const EVP_MD type, ENGINE e, EVP_PKEY *pkey);
	int EVP_DigestSignUpdate(EVP_MD_CTX ctx, const void d, size_t cnt);
	int EVP_DigestSignFinal(EVP_MD_CTX ctx, unsigned char sig, size_t *siglen);

	int EVP_DigestSign(EVP_MD_CTX ctx, unsigned char sigret,
	size_t siglen, const unsigned char tbs,
	size_t tbslen);

	=head1 DESCRIPTION

	The EVP signature routines are a high-level interface to digital signatures.
	Input data is digested first before the signing takes place.

	EVP_DigestSignInit_ex() sets up signing context I<ctx> to use a digest
	with the name I<mdname> and private key I<pkey>. The name of the digest to be
	used is passed to the provider of the signature algorithm in use. How that
	provider interprets the digest name is provider specific. The provider may
	implement that digest directly itself or it may (optionally) choose to fetch it
	(which could result in a digest from a different provider being selected). If the
	provider supports fetching the digest then it may use the I<props> argument for
	the properties to be used during the fetch. Finally, the passed parameters
	I<params>, if not NULL, are set on the context before returning.

	The I<pkey> algorithm is used to fetch a B<EVP_SIGNATURE> method implicitly, to
	be used for the actual signing. See L<provider(7)/Implicit fetch> for
	more information about implicit fetches.

	The OpenSSL default and legacy providers support fetching digests and can fetch
	those digests from any available provider. The OpenSSL fips provider also
	supports fetching digests but will only fetch digests that are themselves
	implemented inside the fips provider.

	I<ctx> must be created with EVP_MD_CTX_new() before calling this function. If
	I<pctx> is not NULL, the EVP_PKEY_CTX of the signing operation will be written
	to I<*pctx>: this can be used to set alternative signing options. Note that any
	existing value in I<*pctx> is overwritten. The EVP_PKEY_CTX value returned must
	not be freed directly by the application if I<ctx> is not assigned an
	EVP_PKEY_CTX value before being passed to EVP_DigestSignInit_ex()
	(which means the EVP_PKEY_CTX is created inside EVP_DigestSignInit_ex()
	and it will be freed automatically when the EVP_MD_CTX is freed). If the
	EVP_PKEY_CTX to be used is created by EVP_DigestSignInit_ex then it
	will use the B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
	specified in I<props>.

	The digest I<mdname> may be NULL if the signing algorithm supports it. The
	I<props> argument can always be NULL.

	No B<EVP_PKEY_CTX> will be created by EVP_DigestSignInit_ex() if the
	passed I<ctx> has already been assigned one via L<EVP_MD_CTX_set_pkey_ctx(3)>.
	See also L<SM2(7)>.

	Only EVP_PKEY types that support signing can be used with these functions. This
	includes MAC algorithms where the MAC generation is considered as a form of
	"signing". Built-in EVP_PKEY types supported by these functions are CMAC,
	Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.

	Not all digests can be used for all key types. The following combinations apply.

	=over 4

	=item DSA

	Supports SHA1, SHA224, SHA256, SHA384 and SHA512

	=item ECDSA

	Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3

	=item RSA with no padding

	Supports no digests (the digest I<type> must be NULL)

	=item RSA with X931 padding

	Supports SHA1, SHA256, SHA384 and SHA512

	=item All other RSA padding types

	Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
	SHA3-224, SHA3-256, SHA3-384, SHA3-512

	=item Ed25519 and Ed448

	Support no digests (the digest I<type> must be NULL)

	=item HMAC

	Supports any digest

	=item CMAC, Poly1305 and SipHash

	Will ignore any digest provided.

	=back

	If RSA-PSS is used and restrictions apply then the digest must match.

	EVP_DigestSignInit() works in the same way as EVP_DigestSignInit_ex()
	except that the I<mdname> parameter will be inferred from the supplied
	digest I<type>, and I<props> will be NULL. Where supplied the ENGINE I<e> will
	be used for the signing and digest algorithm implementations. I<e> may be NULL.

	EVP_DigestSignUpdate() hashes I<cnt> bytes of data at I<d> into the
	signature context I<ctx>. This function can be called several times on the
	same I<ctx> to include additional data.

	Unless I<sig> is NULL EVP_DigestSignFinal() signs the data in I<ctx>
	and places the signature in I<sig>.
	Otherwise the maximum necessary size of the output buffer is written to
	the I<siglen> parameter. If I<sig> is not NULL then before the call the
	I<siglen> parameter should contain the length of the I<sig> buffer. If the
	call is successful the signature is written to I<sig> and the amount of data
	written to I<siglen>.

	EVP_DigestSign() signs I<tbslen> bytes of data at I<tbs> and places the
	signature in I<sig> and its length in I<siglen> in a similar way to
	EVP_DigestSignFinal(). In the event of a failure EVP_DigestSign() cannot be
	called again without reinitialising the EVP_MD_CTX. If I<sig> is NULL before the
	call then I<siglen> will be populated with the required size for the I<sig>
	buffer. If I<sig> is non-NULL before the call then I<siglen> should contain the
	length of the I<sig> buffer.

	=head1 RETURN VALUES

	EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignFinal() and
	EVP_DigestSign() return 1 for success and 0 for failure.

	The error codes can be obtained from L<ERR_get_error(3)>.

	=head1 NOTES

	The B<EVP> interface to digital signatures should almost always be used in
	preference to the low-level interfaces. This is because the code then becomes
	transparent to the algorithm used and much more flexible.

	EVP_DigestSign() is a one shot operation which signs a single block of data
	in one function. For algorithms that support streaming it is equivalent to
	calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which
	do not support streaming (e.g. PureEdDSA) it is the only way to sign data.

	In previous versions of OpenSSL there was a link between message digest types
	and public key algorithms. This meant that "clone" digests such as EVP_dss1()
	needed to be used to sign using SHA1 and DSA. This is no longer necessary and
	the use of clone digest is now discouraged.

	For some key types and parameters the random number generator must be seeded.
	If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
	external circumstances (see L<RAND(7)>), the operation will fail.

	The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
	context. This means that calls to EVP_DigestSignUpdate() and
	EVP_DigestSignFinal() can be called later to digest and sign additional data.

	EVP_DigestSignInit() and EVP_DigestSignInit_ex() functions can be called
	multiple times on a context and the parameters set by previous calls should be
	preserved if the I<pkey> parameter is NULL. The call then just resets the state
	of the I<ctx>.

	The use of EVP_PKEY_get_size() with these functions is discouraged because some
	signature operations may have a signature length which depends on the
	parameters set. As a result EVP_PKEY_get_size() would have to return a value
	which indicates the maximum possible signature for any set of parameters.

	=head1 SEE ALSO

	L<EVP_DigestVerifyInit(3)>,
	L<EVP_DigestInit(3)>,
	L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
	L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
	L<SHA1(3)>, L<openssl-dgst(1)>,
	L<RAND(7)>

	=head1 HISTORY

	EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
	were added in OpenSSL 1.0.0.

	EVP_DigestSignInit_ex() was added in OpenSSL 3.0.

	EVP_DigestSignUpdate() was converted from a macro to a function in OpenSSL 3.0.

	=head1 COPYRIGHT

	Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved.

	Licensed under the Apache License 2.0 (the "License"). You may not use
	this file except in compliance with the License. You can obtain a copy
	in the file LICENSE in the source distribution or at
	L<https://www.openssl.org/source/license.html>.

	=cut