5 EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal,
6 EVP_DigestSign - EVP signing functions
10 #include <openssl/evp.h>
12 int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
13 const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
14 int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
15 int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);
17 int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret,
18 size_t *siglen, const unsigned char *tbs,
23 The EVP signature routines are a high-level interface to digital signatures.
25 EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from
26 ENGINE B<e> and private key B<pkey>. B<ctx> must be created with
27 EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL, the
28 EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can
29 be used to set alternative signing options. Note that any existing value in
30 B<*pctx> is overwritten. The EVP_PKEY_CTX value returned must not be freed
31 directly by the application if B<ctx> is not assigned an EVP_PKEY_CTX value before
32 being passed to EVP_DigestSignInit() (which means the EVP_PKEY_CTX is created
33 inside EVP_DigestSignInit() and it will be freed automatically when the
36 The digest B<type> may be NULL if the signing algorithm supports it.
38 No B<EVP_PKEY_CTX> will be created by EVP_DigestSignInit() if the passed B<ctx>
39 has already been assigned one via L<EVP_MD_CTX_set_pkey_ctx(3)>. See also L<SM2(7)>.
41 Only EVP_PKEY types that support signing can be used with these functions. This
42 includes MAC algorithms where the MAC generation is considered as a form of
43 "signing". Built-in EVP_PKEY types supported by these functions are CMAC,
44 Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.
46 Not all digests can be used for all key types. The following combinations apply.
52 Supports SHA1, SHA224, SHA256, SHA384 and SHA512
56 Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3
58 =item RSA with no padding
60 Supports no digests (the digest B<type> must be NULL)
62 =item RSA with X931 padding
64 Supports SHA1, SHA256, SHA384 and SHA512
66 =item All other RSA padding types
68 Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
69 SHA3-224, SHA3-256, SHA3-384, SHA3-512
71 =item Ed25519 and Ed448
73 Support no digests (the digest B<type> must be NULL)
79 =item CMAC, Poly1305 and SipHash
81 Will ignore any digest provided.
85 If RSA-PSS is used and restrictions apply then the digest must match.
87 EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the
88 signature context B<ctx>. This function can be called several times on the
89 same B<ctx> to include additional data. This function is currently implemented
92 EVP_DigestSignFinal() signs the data in B<ctx> and places the signature in B<sig>.
93 If B<sig> is B<NULL> then the maximum size of the output buffer is written to
94 the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the
95 B<siglen> parameter should contain the length of the B<sig> buffer. If the
96 call is successful the signature is written to B<sig> and the amount of data
99 EVP_DigestSign() signs B<tbslen> bytes of data at B<tbs> and places the
100 signature in B<sig> and its length in B<siglen> in a similar way to
101 EVP_DigestSignFinal().
105 EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignFinal() and
106 EVP_DigestSign() return 1 for success and 0 for failure.
108 The error codes can be obtained from L<ERR_get_error(3)>.
112 The B<EVP> interface to digital signatures should almost always be used in
113 preference to the low-level interfaces. This is because the code then becomes
114 transparent to the algorithm used and much more flexible.
116 EVP_DigestSign() is a one shot operation which signs a single block of data
117 in one function. For algorithms that support streaming it is equivalent to
118 calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which
119 do not support streaming (e.g. PureEdDSA) it is the only way to sign data.
121 In previous versions of OpenSSL there was a link between message digest types
122 and public key algorithms. This meant that "clone" digests such as EVP_dss1()
123 needed to be used to sign using SHA1 and DSA. This is no longer necessary and
124 the use of clone digest is now discouraged.
126 For some key types and parameters the random number generator must be seeded.
127 If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
128 external circumstances (see L<RAND(7)>), the operation will fail.
130 The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
131 context. This means that calls to EVP_DigestSignUpdate() and
132 EVP_DigestSignFinal() can be called later to digest and sign additional data.
134 Since only a copy of the digest context is ever finalized, the context must
135 be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
138 The use of EVP_PKEY_size() with these functions is discouraged because some
139 signature operations may have a signature length which depends on the
140 parameters set. As a result EVP_PKEY_size() would have to return a value
141 which indicates the maximum possible signature for any set of parameters.
145 L<EVP_DigestVerifyInit(3)>,
146 L<EVP_DigestInit(3)>,
147 L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
148 L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
149 L<SHA1(3)>, L<dgst(1)>,
154 EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
155 were added in OpenSSL 1.0.0.
159 Copyright 2006-2020 The OpenSSL Project Authors. All Rights Reserved.
161 Licensed under the OpenSSL license (the "License"). You may not use
162 this file except in compliance with the License. You can obtain a copy
163 in the file LICENSE in the source distribution or at
164 L<https://www.openssl.org/source/license.html>.