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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
75394189 DSH |
5 | EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal, |
6 | EVP_DigestSign - EVP signing functions | |
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7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/evp.h> | |
11 | ||
12 | int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx, | |
1bc74519 | 13 | const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey); |
8bdce8d1 | 14 | int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); |
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15 | int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen); |
16 | ||
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17 | int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret, |
18 | size_t *siglen, const unsigned char *tbs, | |
19 | size_t tbslen); | |
20 | ||
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21 | =head1 DESCRIPTION |
22 | ||
23 | The EVP signature routines are a high level interface to digital signatures. | |
24 | ||
25 | EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from | |
0c714ba2 | 26 | ENGINE B<e> and private key B<pkey>. B<ctx> must be created with |
25191fff | 27 | EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL the |
29cf84c6 | 28 | EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can |
be93b0e8 MC |
29 | be used to set alternative signing options. The digest B<type> may be NULL if |
30 | the signing algorithm supports it. | |
31 | ||
32 | Only EVP_PKEY types that support signing can be used with these functions. This | |
33 | includes MAC algorithms where the MAC generation is considered as a form of | |
34 | "signing." Built-in EVP_PKEY types supported by these functions are CMAC, | |
c6378913 | 35 | Poly1305, DSA, ECDSA, HMAC, RSA, SipHash, Ed25519 and Ed448. |
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36 | |
37 | Not all digests can be used for all key types. The following combinations apply. | |
38 | ||
39 | =over 4 | |
40 | ||
41 | =item DSA | |
42 | ||
43 | Supports SHA1, SHA224, SHA256, SHA384 and SHA512 | |
44 | ||
45 | =item ECDSA | |
46 | ||
47 | Supports SHA1, SHA224, SHA256, SHA384, SHA512 and SM3 | |
48 | ||
49 | =item RSA with no padding | |
50 | ||
51 | Supports no digests (the digest B<type> must be NULL) | |
52 | ||
53 | =item RSA with X931 padding | |
54 | ||
55 | Supports SHA1, SHA256, SHA384 and SHA512 | |
56 | ||
57 | =item All other RSA padding types | |
58 | ||
59 | Support SHA1, SHA224, SHA256, SHA384, SHA512, MD5, MD5_SHA1, MD2, MD4, MDC2, | |
60 | SHA3-224, SHA3-256, SHA3-384, SHA3-512 | |
61 | ||
62 | =item Ed25519 and Ed448 | |
63 | ||
64 | Support no digests (the digest B<type> must be NULL) | |
65 | ||
66 | =item HMAC | |
67 | ||
68 | Supports any digest | |
69 | ||
70 | =item CMAC, Poly1305 and SipHash | |
71 | ||
72 | Will ignore any digest provided. | |
73 | ||
74 | =back | |
75 | ||
76 | If RSA-PSS is used and restrictions apply then the digest must match. | |
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77 | |
78 | EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the | |
79 | signature context B<ctx>. This function can be called several times on the | |
80 | same B<ctx> to include additional data. This function is currently implemented | |
186bb907 | 81 | using a macro. |
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82 | |
83 | EVP_DigestSignFinal() signs the data in B<ctx> places the signature in B<sig>. | |
84 | If B<sig> is B<NULL> then the maximum size of the output buffer is written to | |
85 | the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the | |
86 | B<siglen> parameter should contain the length of the B<sig> buffer, if the | |
87 | call is successful the signature is written to B<sig> and the amount of data | |
88 | written to B<siglen>. | |
89 | ||
75394189 | 90 | EVP_DigestSign() signs B<tbslen> bytes of data at B<tbs> and places the |
27b138e9 | 91 | signature in B<sig> and its length in B<siglen> in a similar way to |
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92 | EVP_DigestSignFinal(). |
93 | ||
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94 | =head1 RETURN VALUES |
95 | ||
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96 | EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignaFinal() and |
97 | EVP_DigestSign() return 1 for success and 0 or a negative value for failure. In | |
98 | particular a return value of -2 indicates the operation is not supported by the | |
99 | public key algorithm. | |
29cf84c6 | 100 | |
9b86974e | 101 | The error codes can be obtained from L<ERR_get_error(3)>. |
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102 | |
103 | =head1 NOTES | |
104 | ||
105 | The B<EVP> interface to digital signatures should almost always be used in | |
106 | preference to the low level interfaces. This is because the code then becomes | |
107 | transparent to the algorithm used and much more flexible. | |
108 | ||
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109 | EVP_DigestSign() is a one shot operation which signs a single block of data |
110 | in one function. For algorithms that support streaming it is equivalent to | |
111 | calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which | |
112 | do not support streaming (e.g. PureEdDSA) it is the only way to sign data. | |
75394189 | 113 | |
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114 | In previous versions of OpenSSL there was a link between message digest types |
115 | and public key algorithms. This meant that "clone" digests such as EVP_dss1() | |
116 | needed to be used to sign using SHA1 and DSA. This is no longer necessary and | |
117 | the use of clone digest is now discouraged. | |
118 | ||
119 | For some key types and parameters the random number generator must be seeded | |
1bc74519 | 120 | or the operation will fail. |
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121 | |
122 | The call to EVP_DigestSignFinal() internally finalizes a copy of the digest | |
123 | context. This means that calls to EVP_DigestSignUpdate() and | |
124 | EVP_DigestSignFinal() can be called later to digest and sign additional data. | |
125 | ||
126 | Since only a copy of the digest context is ever finalized the context must | |
c12a2d27 | 127 | be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak |
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128 | will occur. |
129 | ||
130 | The use of EVP_PKEY_size() with these functions is discouraged because some | |
131 | signature operations may have a signature length which depends on the | |
132 | parameters set. As a result EVP_PKEY_size() would have to return a value | |
133 | which indicates the maximum possible signature for any set of parameters. | |
134 | ||
135 | =head1 SEE ALSO | |
136 | ||
9b86974e | 137 | L<EVP_DigestVerifyInit(3)>, |
73fb82b7 | 138 | L<EVP_DigestInit(3)>, |
b97fdb57 RL |
139 | L<evp(7)>, L<HMAC(3)>, L<MD2(3)>, |
140 | L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>, | |
141 | L<SHA1(3)>, L<dgst(1)> | |
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142 | |
143 | =head1 HISTORY | |
144 | ||
1bc74519 | 145 | EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal() |
fb552ac6 | 146 | were first added to OpenSSL 1.0.0. |
29cf84c6 | 147 | |
e2f92610 RS |
148 | =head1 COPYRIGHT |
149 | ||
28428130 | 150 | Copyright 2006-2018 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 RS |
151 | |
152 | Licensed under the OpenSSL license (the "License"). You may not use | |
153 | this file except in compliance with the License. You can obtain a copy | |
154 | in the file LICENSE in the source distribution or at | |
155 | L<https://www.openssl.org/source/license.html>. | |
156 | ||
157 | =cut |