5 EVP_MAC, EVP_MAC_CTX, EVP_MAC_CTX_new, EVP_MAC_CTX_new_id, EVP_MAC_CTX_free,
6 EVP_MAC_CTX_copy, EVP_MAC_CTX_mac, EVP_MAC_size, EVP_MAC_init, EVP_MAC_update,
7 EVP_MAC_final, EVP_MAC_ctrl, EVP_MAC_vctrl, EVP_MAC_ctrl_str,
8 EVP_MAC_str2ctrl, EVP_MAC_hex2ctrl, EVP_MAC_nid, EVP_MAC_name,
9 EVP_get_macbyname, EVP_get_macbynid, EVP_get_macbyobj - EVP MAC routines
13 #include <openssl/evp.h>
15 typedef struct evp_mac_st EVP_MAC;
16 typedef struct evp_mac_ctx_st EVP_MAC_CTX;
18 EVP_MAC_CTX *EVP_MAC_CTX_new(const EVP_MAC *mac);
19 EVP_MAC_CTX *EVP_MAC_CTX_new_id(int nid);
20 void EVP_MAC_CTX_free(EVP_MAC_CTX *ctx);
21 int EVP_MAC_CTX_copy(EVP_MAC_CTX *dest, EVP_MAC_CTX *src);
22 const EVP_MAC *EVP_MAC_CTX_mac(EVP_MAC_CTX *ctx);
23 size_t EVP_MAC_size(EVP_MAC_CTX *ctx);
24 int EVP_MAC_init(EVP_MAC_CTX *ctx);
25 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
26 int EVP_MAC_final(EVP_MAC_CTX *ctx, unsigned char *out, size_t *poutlen);
27 int EVP_MAC_ctrl(EVP_MAC_CTX *ctx, int cmd, ...);
28 int EVP_MAC_vctrl(EVP_MAC_CTX *ctx, int cmd, va_list args);
29 int EVP_MAC_ctrl_str(EVP_MAC_CTX *ctx, const char *type, const char *value);
30 int EVP_MAC_str2ctrl(EVP_MAC_CTX *ctx, int cmd, const char *value);
31 int EVP_MAC_hex2ctrl(EVP_MAC_CTX *ctx, int cmd, const char *value);
32 int EVP_MAC_nid(const EVP_MAC *mac);
33 const char *EVP_MAC_name(const EVP_MAC *mac);
34 const EVP_MAC *EVP_get_macbyname(const char *name);
35 const EVP_MAC *EVP_get_macbynid(int nid);
36 const EVP_MAC *EVP_get_macbyobj(const ASN1_OBJECT *o);
40 These types and functions help the application to calculate MACs of
41 different types and with different underlying algorithms if there are
44 MACs are a bit complex insofar that some of them use other algorithms
45 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
46 Therefore, there are sometimes two contexts to keep track of, one for
47 the MAC algorithm itself and one for the underlying computation
48 algorithm if there is one.
50 To make things less ambiguous, this manual talks about a "context" or
51 "MAC context", which is to denote the MAC level context, and about a
52 "underlying context", or "computation context", which is to denote the
53 context for the underlying computation algorithm if there is one.
57 B<EVP_MAC> is a type that holds the implementation of a MAC.
59 B<EVP_MAC_CTX> is a context type that holds internal MAC information
60 as well as a reference to a computation context, for those MACs that
61 rely on an underlying computation algorithm.
63 =head2 Context manipulation functions
65 EVP_MAC_CTX_new() creates a new context for the MAC type C<mac>.
66 EVP_MAC_CTX_new_id() creates a new context for the numerical MAC
68 The created context can then be used with most other functions
71 EVP_MAC_CTX_free() frees the contents of the context, including an
72 underlying context if there is one, as well as the context itself.
73 B<NULL> is a valid parameter, for which this function is a no-op.
75 EVP_MAC_CTX_copy() makes a deep copy of the C<src> context to the
77 The C<dest> context I<must> have been created before calling this
80 EVP_MAC_CTX_mac() returns the B<EVP_MAC> associated with the context
83 =head2 Computing functions
85 EVP_MAC_init() sets up the underlying context with information given
86 through diverse controls.
87 This should be called before calling EVP_MAC_update() and
90 EVP_MAC_reset() resets the computation for the given context.
91 This may not be supported by the MAC implementation.
93 EVP_MAC_update() adds C<datalen> bytes from C<data> to the MAC input.
95 EVP_MAC_final() does the final computation and stores the result in
96 the memory pointed at by C<out>, and sets its size in the B<size_t>
97 the C<poutlen> points at.
98 If C<out> is B<NULL>, then no computation is made.
99 To figure out what the output length will be and allocate space for it
100 dynamically, simply call with C<out> being B<NULL> and C<poutlen>
101 pointing at a valid location, then allocate space and make a second
102 call with C<out> pointing at the allocated space.
104 EVP_MAC_ctrl() is used to manipulate or get information on aspects of
105 the MAC which may vary depending on the MAC algorithm or its
107 This includes the MAC key, and for MACs that use other algorithms to
108 do their computation, this is also the way to tell it which one to
110 This functions takes variable arguments, the exact expected arguments
112 EVP_MAC_ctrl() can be called both before and after EVP_MAC_init(), but
113 the effect will depend on what control is being use.
114 See </CONTROLS> below for a description of standard controls.
116 EVP_MAC_vctrl() is the variant of EVP_MAC_ctrl() that takes a
117 C<va_list> argument instead of variadic arguments.
119 EVP_MAC_ctrl_str() is an alternative to EVP_MAC_ctrl() to control the
120 MAC implementation as E<lt> C<type>, C<value> E<gt> pairs.
121 The MAC implementation documentation should specify what control type
122 strings are accepted.
124 EVP_MAC_str2ctrl() and EVP_MAC_hex2ctrl() are helper functions to
125 control the MAC implementation with raw strings or with strings
126 containing hexadecimal numbers.
127 The latter are decoded into bitstrings that are sent on to
130 =head2 Information functions
132 EVP_MAC_size() returns the MAC output size for the given context.
134 EVP_MAC_nid() returns the numeric identity of the given MAC implementation.
136 EVP_MAC_name() returns the name of the given MAC implementation.
138 =head2 Object database functions
140 EVP_get_macbyname() fetches a MAC implementation from the object
143 EVP_get_macbynid() fetches a MAC implementation from the object
144 database by numeric identity.
146 EVP_get_macbyobj() fetches a MAC implementation from the object
147 database by ASN.1 OBJECT (i.e. an encoded OID).
151 The standard controls are:
155 =item B<EVP_MAC_CTRL_SET_KEY>
157 This control expects two arguments: C<unsigned char *key>, C<size_t keylen>
159 These will set the MAC key from the given string of the given length.
160 The string may be any bitstring, and can contain NUL bytes.
162 For MACs that use an underlying computation algorithm, the algorithm
163 I<must> be set first, see B<EVP_MAC_CTRL_SET_ENGINE>,
164 B<EVP_MAC_CTRL_SET_MD> and B<EVP_MAC_CTRL_SET_CIPHER> below.
166 =item B<EVP_MAC_CTRL_SET_IV>
168 This control expects two arguments: C<unsigned char *key>, C<size_t keylen>
170 Some MAC implementations require an IV, this control sets the IV.
172 =item B<EVP_MAC_CTRL_SET_CUSTOM>
174 This control expects two arguments: C<unsigned char *key>, C<size_t keylen>
176 Some MAC implementations (KMAC) require an Customization String,
177 this control sets the Customization String. The default value is "".
179 =item B<EVP_MAC_CTRL_SET_XOF>
181 This control expects one argument: C<int xof>
183 This option is used by KMAC.
186 =item B<EVP_MAC_CTRL_SET_FLAGS>
188 This control expects one argument: C<unsigned long flags>
190 These will set the MAC flags to the given numbers.
191 Some MACs do not support this option.
193 =item B<EVP_MAC_CTRL_SET_ENGINE>
195 =item B<EVP_MAC_CTRL_SET_MD>
197 =item B<EVP_MAC_CTRL_SET_CIPHER>
199 For MAC implementations that use an underlying computation algorithm,
200 these controls set what the algorithm should be, and the engine that
201 implements the algorithm if needed.
203 B<EVP_MAC_CTRL_SET_ENGINE> takes one argument: C<ENGINE *>
205 B<EVP_MAC_CTRL_SET_MD> takes one argument: C<EVP_MD *>
207 B<EVP_MAC_CTRL_SET_CIPHER> takes one argument: C<EVP_CIPHER *>
209 =item B<EVP_MAC_CTRL_SET_SIZE>
211 For MAC implementations that support it, set the output size that
212 EVP_MAC_final() should produce.
213 The allowed sizes vary between MAC implementations.
217 All these control should be used before the calls to any of
218 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
220 Anything else may give undefined results.
224 EVP_get_macbynid(), EVP_get_macbyobj() and EVP_MAC_name() are
225 implemented as a macro.
229 EVP_MAC_CTX_new() and EVP_MAC_CTX_new_id() return a pointer to a newly
230 created EVP_MAC_CTX, or NULL if allocation failed.
232 EVP_MAC_CTX_free() returns nothing at all.
234 EVP_MAC_CTX_copy(), EVP_MAC_reset(), EVP_MAC_init(), EVP_MAC_update(),
235 and EVP_MAC_final() return 1 on success, 0 on error.
237 EVP_MAC_ctrl(), EVP_MAC_ctrl_str(), EVP_MAC_str2ctrl() and
238 EVP_MAC_hex2ctrl() return 1 on success and 0 or a negative value on
240 In particular, the value -2 indicates that the given control type
241 isn't supported by the MAC implementation.
243 EVP_MAC_size() returns the expected output size, or 0 if it isn't
245 If it isn't set, a call to EVP_MAC_init() should get it set.
247 EVP_MAC_nid() returns the numeric identity for the given C<mac>.
249 EVP_MAC_name() returns the name for the given C<mac>, if it has been
250 added to the object database.
252 EVP_add_mac() returns 1 if the given C<mac> was successfully added to
253 the object database, otherwise 0.
255 EVP_get_macbyname(), EVP_get_macbynid() and EVP_get_macbyobj() return
256 the request MAC implementation, if it exists in the object database,
267 #include <openssl/evp.h>
268 #include <openssl/err.h>
270 int ctrl_ign_unsupported(EVP_MAC_CTX *ctx, int cmd, ...)
276 rv = EVP_MAC_vctrl(ctx, cmd, args);
280 rv = 1; /* Ignore unsupported, pretend it worked fine */
287 EVP_get_macbyname(getenv("MY_MAC"));
288 const EVP_CIPHER *cipher =
289 EVP_get_cipherbyname(getenv("MY_MAC_CIPHER"));
290 const EVP_MD *digest =
291 EVP_get_digestbyname(getenv("MY_MAC_DIGEST"));
292 const char *key = getenv("MY_KEY");
293 EVP_MAC_CTX *ctx = NULL;
295 unsigned char buf[4096];
303 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
305 && !ctrl_ign_unsupported(ctx, EVP_MAC_CTRL_SET_CIPHER, cipher))
307 && !ctrl_ign_unsupported(ctx, EVP_MAC_CTRL_SET_MD, digest))
308 || EVP_MAC_ctrl(ctx, EVP_MAC_CTRL_SET_KEY, key, strlen(key)) <= 0)
311 if (!EVP_MAC_init(ctx))
314 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) < 0) {
315 if (!EVP_MAC_update(ctx, buf, read_l))
319 if (!EVP_MAC_final(ctx, buf, &final_l))
323 for (i = 0; i < final_l; i++)
324 printf("%02X", buf[i]);
327 EVP_MAC_CTX_free(ctx);
331 EVP_MAC_CTX_free(ctx);
332 fprintf(stderr, "Something went wrong\n");
333 ERR_print_errors_fp(stderr);
337 A run of this program, called with correct environment variables, can
340 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
341 LD_LIBRARY_PATH=. ./foo < foo.c
342 Result: ECCAAFF041B22A2299EB90A1B53B6D45
344 (in this example, that program was stored in F<foo.c> and compiled to
353 L<EVP_MAC_SIPHASH(7)>,
354 L<EVP_MAC_POLY1305(7)>
358 Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
360 Licensed under the Apache License 2.0 (the "License"). You may not use
361 this file except in compliance with the License. You can obtain a copy
362 in the file LICENSE in the source distribution or at
363 L<https://www.openssl.org/source/license.html>.