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 (it will be freed automatically when the EVP_MD_CTX
32 is freed). The digest B<type> may be NULL if the signing algorithm supports it.
34 Only EVP_PKEY types that support signing can be used with these functions. This
35 includes MAC algorithms where the MAC generation is considered as a form of
36 "signing". Built-in EVP_PKEY types supported by these functions are CMAC,
37 Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.
39 Not all digests can be used for all key types. The following combinations apply.
45 Supports SHA1, SHA224, SHA256, SHA384 and SHA512
49 Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3
51 =item RSA with no padding
53 Supports no digests (the digest B<type> must be NULL)
55 =item RSA with X931 padding
57 Supports SHA1, SHA256, SHA384 and SHA512
59 =item All other RSA padding types
61 Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
62 SHA3-224, SHA3-256, SHA3-384, SHA3-512
64 =item Ed25519 and Ed448
66 Support no digests (the digest B<type> must be NULL)
72 =item CMAC, Poly1305 and SipHash
74 Will ignore any digest provided.
78 If RSA-PSS is used and restrictions apply then the digest must match.
80 EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the
81 signature context B<ctx>. This function can be called several times on the
82 same B<ctx> to include additional data. This function is currently implemented
85 EVP_DigestSignFinal() signs the data in B<ctx> and places the signature in B<sig>.
86 If B<sig> is B<NULL> then the maximum size of the output buffer is written to
87 the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the
88 B<siglen> parameter should contain the length of the B<sig> buffer. If the
89 call is successful the signature is written to B<sig> and the amount of data
92 EVP_DigestSign() signs B<tbslen> bytes of data at B<tbs> and places the
93 signature in B<sig> and its length in B<siglen> in a similar way to
94 EVP_DigestSignFinal().
98 EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignaFinal() and
99 EVP_DigestSign() return 1 for success and 0 or a negative value for failure. In
100 particular, a return value of -2 indicates the operation is not supported by the
101 public key algorithm.
103 The error codes can be obtained from L<ERR_get_error(3)>.
107 The B<EVP> interface to digital signatures should almost always be used in
108 preference to the low level interfaces. This is because the code then becomes
109 transparent to the algorithm used and much more flexible.
111 EVP_DigestSign() is a one shot operation which signs a single block of data
112 in one function. For algorithms that support streaming it is equivalent to
113 calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which
114 do not support streaming (e.g. PureEdDSA) it is the only way to sign data.
116 In previous versions of OpenSSL there was a link between message digest types
117 and public key algorithms. This meant that "clone" digests such as EVP_dss1()
118 needed to be used to sign using SHA1 and DSA. This is no longer necessary and
119 the use of clone digest is now discouraged.
121 For some key types and parameters the random number generator must be seeded
122 or the operation will fail.
124 The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
125 context. This means that calls to EVP_DigestSignUpdate() and
126 EVP_DigestSignFinal() can be called later to digest and sign additional data.
128 Since only a copy of the digest context is ever finalized, the context must
129 be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
132 The use of EVP_PKEY_size() with these functions is discouraged because some
133 signature operations may have a signature length which depends on the
134 parameters set. As a result EVP_PKEY_size() would have to return a value
135 which indicates the maximum possible signature for any set of parameters.
139 L<EVP_DigestVerifyInit(3)>,
140 L<EVP_DigestInit(3)>,
141 L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
142 L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
143 L<SHA1(3)>, L<dgst(1)>
147 EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
148 were first added to OpenSSL 1.0.0.
152 Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved.
154 Licensed under the OpenSSL license (the "License"). You may not use
155 this file except in compliance with the License. You can obtain a copy
156 in the file LICENSE in the source distribution or at
157 L<https://www.openssl.org/source/license.html>.