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_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.
+be used to set alternative signing options. Note that any existing value in
+B<*pctx> is overwritten. The EVP_PKEY_CTX value returned must not be freed
+directly by the application if B<ctx> is not assigned an EVP_PKEY_CTX value before
+being passed to EVP_DigestSignInit() (which means the EVP_PKEY_CTX is created
+inside EVP_DigestSignInit() and it will be freed automatically when the
+EVP_MD_CTX is freed).
+
+The digest B<type> may be NULL if the signing algorithm supports it.
+
+No B<EVP_PKEY_CTX> will be created by EVP_DigestSignInit() if the passed B<ctx>
+has already been assigned one via L<EVP_MD_CTX_set_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 B<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 B<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_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_DigestSignFinal() signs the data in B<ctx> places the signature in B<sig>.
+EVP_DigestSignFinal() signs the data in B<ctx> and 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
+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_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
+particular, a return value of -2 indicates the operation is not supported by the
public key algorithm.
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<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.
=head1 COPYRIGHT
-Copyright 2006-2017 The OpenSSL Project Authors. All Rights Reserved.
+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