=head1 NAME
-EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal,
-EVP_DigestSign - EVP signing functions
+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, const char *props,
+ EVP_PKEY *pkey);
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);
=head1 DESCRIPTION
The EVP signature routines are a high level interface to digital signatures.
-
-EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from
-ENGINE B<e> and private key B<pkey>. B<ctx> must be created with
-EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL the
-EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can
-be used to set alternative signing options. The digest B<type> may be NULL if
-the signing algorithm supports it.
+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.
+
+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 implict 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).
+
+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,
+"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.
=item RSA with no padding
-Supports no digests (the digest B<type> must be NULL)
+Supports no digests (the digest I<type> must be NULL)
=item RSA with X931 padding
=item Ed25519 and Ed448
-Support no digests (the digest B<type> must be NULL)
+Support no digests (the digest I<type> must be NULL)
=item HMAC
If RSA-PSS is used and restrictions apply then the digest must match.
-EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the
-signature context B<ctx>. This function can be called several times on the
-same B<ctx> to include additional data. This function is currently implemented
-using a macro.
+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.
-EVP_DigestSignFinal() signs the data in B<ctx> places the signature in B<sig>.
-If B<sig> is B<NULL> then the maximum size of the output buffer is written to
-the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the
-B<siglen> parameter should contain the length of the B<sig> buffer, if the
-call is successful the signature is written to B<sig> and the amount of data
-written to B<siglen>.
+EVP_DigestSignFinal() signs the data in I<ctx> and places the signature in I<sig>.
+If I<sig> is NULL then the maximum 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 B<tbslen> bytes of data at B<tbs> and places the
-signature in B<sig> and its length in B<siglen> in a similar way to
+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().
=head1 RETURN VALUES
EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignaFinal() and
-EVP_DigestSign() return 1 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.
+EVP_DigestSign() return 1 for success and 0 for failure.
The error codes can be obtained from L<ERR_get_error(3)>.
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
-or the operation will fail.
+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.
-Since only a copy of the digest context is ever finalized the context must
+Since only a copy of the digest context is ever finalized, the context must
be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
will occur.
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<dgst(1)>
+L<SHA1(3)>, L<openssl-dgst(1)>,
+L<RAND(7)>
=head1 HISTORY
EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
-were first added to OpenSSL 1.0.0.
+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 2006-2018 The OpenSSL Project Authors. All Rights Reserved.
-Licensed under the OpenSSL license (the "License"). You may not use
+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>.
projects / openssl.git / blobdiff