5 EVP_DigestSignInit_ex, EVP_DigestSignInit, EVP_DigestSignUpdate,
6 EVP_DigestSignFinal, EVP_DigestSign - EVP signing functions
10 #include <openssl/evp.h>
12 int EVP_DigestSignInit_ex(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
13 const char *mdname, OSSL_LIB_CTX *libctx,
14 const char *props, EVP_PKEY *pkey);
15 int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
16 const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
17 int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
18 int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);
20 int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret,
21 size_t *siglen, const unsigned char *tbs,
26 The EVP signature routines are a high-level interface to digital signatures.
27 Input data is digested first before the signing takes place.
29 EVP_DigestSignInit_ex() sets up signing context I<ctx> to use a digest
30 with the name I<mdname> and private key I<pkey>. The name of the digest to be
31 used is passed to the provider of the signature algorithm in use. How that
32 provider interprets the digest name is provider specific. The provider may
33 implement that digest directly itself or it may (optionally) choose to fetch it
34 (which could result in a digest from a different provider being selected). If the
35 provider supports fetching the digest then it may use the I<props> argument for
36 the properties to be used during the fetch.
38 The I<pkey> algorithm is used to fetch a B<EVP_SIGNATURE> method implicitly, to
39 be used for the actual signing. See L<provider(7)/Implicit fetch> for
40 more information about implicit fetches.
42 The OpenSSL default and legacy providers support fetching digests and can fetch
43 those digests from any available provider. The OpenSSL fips provider also
44 supports fetching digests but will only fetch digests that are themselves
45 implemented inside the fips provider.
47 I<ctx> must be created with EVP_MD_CTX_new() before calling this function. If
48 I<pctx> is not NULL, the EVP_PKEY_CTX of the signing operation will be written
49 to I<*pctx>: this can be used to set alternative signing options. Note that any
50 existing value in I<*pctx> is overwritten. The EVP_PKEY_CTX value returned must
51 not be freed directly by the application if I<ctx> is not assigned an
52 EVP_PKEY_CTX value before being passed to EVP_DigestSignInit_ex()
53 (which means the EVP_PKEY_CTX is created inside EVP_DigestSignInit_ex()
54 and it will be freed automatically when the EVP_MD_CTX is freed). If the
55 EVP_PKEY_CTX to be used is created by EVP_DigestSignInit_ex then it
56 will use the B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
57 specified in I<props>.
59 The digest I<mdname> may be NULL if the signing algorithm supports it. The
60 I<props> argument can always be NULL.
62 No B<EVP_PKEY_CTX> will be created by EVP_DigestSignInit_ex() if the
63 passed I<ctx> has already been assigned one via L<EVP_MD_CTX_set_pkey_ctx(3)>.
66 Only EVP_PKEY types that support signing can be used with these functions. This
67 includes MAC algorithms where the MAC generation is considered as a form of
68 "signing". Built-in EVP_PKEY types supported by these functions are CMAC,
69 Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448.
71 Not all digests can be used for all key types. The following combinations apply.
77 Supports SHA1, SHA224, SHA256, SHA384 and SHA512
81 Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3
83 =item RSA with no padding
85 Supports no digests (the digest I<type> must be NULL)
87 =item RSA with X931 padding
89 Supports SHA1, SHA256, SHA384 and SHA512
91 =item All other RSA padding types
93 Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2,
94 SHA3-224, SHA3-256, SHA3-384, SHA3-512
96 =item Ed25519 and Ed448
98 Support no digests (the digest I<type> must be NULL)
104 =item CMAC, Poly1305 and SipHash
106 Will ignore any digest provided.
110 If RSA-PSS is used and restrictions apply then the digest must match.
112 EVP_DigestSignInit() works in the same way as EVP_DigestSignInit_ex()
113 except that the I<mdname> parameter will be inferred from the supplied
114 digest I<type>, and I<props> will be NULL. Where supplied the ENGINE I<e> will
115 be used for the signing and digest algorithm implementations. I<e> may be NULL.
117 EVP_DigestSignUpdate() hashes I<cnt> bytes of data at I<d> into the
118 signature context I<ctx>. This function can be called several times on the
119 same I<ctx> to include additional data.
121 Unless I<sig> is NULL EVP_DigestSignFinal() signs the data in I<ctx>
122 and places the signature in I<sig>.
123 Otherwise the maximum necessary size of the output buffer is written to
124 the I<siglen> parameter. If I<sig> is not NULL then before the call the
125 I<siglen> parameter should contain the length of the I<sig> buffer. If the
126 call is successful the signature is written to I<sig> and the amount of data
127 written to I<siglen>.
129 EVP_DigestSign() signs I<tbslen> bytes of data at I<tbs> and places the
130 signature in I<sig> and its length in I<siglen> in a similar way to
131 EVP_DigestSignFinal().
135 EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignFinal() and
136 EVP_DigestSign() return 1 for success and 0 for failure.
138 The error codes can be obtained from L<ERR_get_error(3)>.
142 The B<EVP> interface to digital signatures should almost always be used in
143 preference to the low-level interfaces. This is because the code then becomes
144 transparent to the algorithm used and much more flexible.
146 EVP_DigestSign() is a one shot operation which signs a single block of data
147 in one function. For algorithms that support streaming it is equivalent to
148 calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which
149 do not support streaming (e.g. PureEdDSA) it is the only way to sign data.
151 In previous versions of OpenSSL there was a link between message digest types
152 and public key algorithms. This meant that "clone" digests such as EVP_dss1()
153 needed to be used to sign using SHA1 and DSA. This is no longer necessary and
154 the use of clone digest is now discouraged.
156 For some key types and parameters the random number generator must be seeded.
157 If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to
158 external circumstances (see L<RAND(7)>), the operation will fail.
160 The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
161 context. This means that calls to EVP_DigestSignUpdate() and
162 EVP_DigestSignFinal() can be called later to digest and sign additional data.
164 Since only a copy of the digest context is ever finalized, the context must
165 be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
168 The use of EVP_PKEY_get_size() with these functions is discouraged because some
169 signature operations may have a signature length which depends on the
170 parameters set. As a result EVP_PKEY_get_size() would have to return a value
171 which indicates the maximum possible signature for any set of parameters.
175 L<EVP_DigestVerifyInit(3)>,
176 L<EVP_DigestInit(3)>,
177 L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
178 L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
179 L<SHA1(3)>, L<openssl-dgst(1)>,
184 EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
185 were added in OpenSSL 1.0.0.
187 EVP_DigestSignInit_ex() was added in OpenSSL 3.0.
189 EVP_DigestSignUpdate() was converted from a macro to a function in OpenSSL 3.0.
193 Copyright 2006-2020 The OpenSSL Project Authors. All Rights Reserved.
195 Licensed under the Apache License 2.0 (the "License"). You may not use
196 this file except in compliance with the License. You can obtain a copy
197 in the file LICENSE in the source distribution or at
198 L<https://www.openssl.org/source/license.html>.