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_FLAGS>
168 This control expects one arguments: C<unsigned long flags>
170 These will set the MAC flags to the given numbers.
171 Some MACs do not support this option.
173 =item B<EVP_MAC_CTRL_SET_ENGINE>
175 =item B<EVP_MAC_CTRL_SET_MD>
177 =item B<EVP_MAC_CTRL_SET_CIPHER>
179 For MAC implementations that use an underlying computation algorithm,
180 these controls set what the algorithm should be, and the engine that
181 implements the algorithm if needed.
183 B<EVP_MAC_CTRL_SET_ENGINE> takes one argument: C<ENGINE *>
185 B<EVP_MAC_CTRL_SET_MD> takes one argument: C<EVP_MD *>
187 B<EVP_MAC_CTRL_SET_CIPHER> takes one argument: C<EVP_CIPHER *>
189 =item B<EVP_MAC_CTRL_SET_SIZE>
191 For MAC implementations that support it, set the output size that
192 EVP_MAC_final() should produce.
193 The allowed sizes vary between MAC implementations.
197 All these control should be used before the calls to any of
198 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
200 Anything else may give undefined results.
204 EVP_get_macbynid(), EVP_get_macbyobj() and EVP_MAC_name() are
205 implemented as a macro.
209 EVP_MAC_CTX_new() and EVP_MAC_CTX_new_id() return a pointer to a newly
210 created EVP_MAC_CTX, or NULL if allocation failed.
212 EVP_MAC_CTX_free() returns nothing at all.
214 EVP_MAC_CTX_copy(), EVP_MAC_reset(), EVP_MAC_init(), EVP_MAC_update(),
215 and EVP_MAC_final() return 1 on success, 0 on error.
217 EVP_MAC_ctrl(), EVP_MAC_ctrl_str(), EVP_MAC_str2ctrl() and
218 EVP_MAC_hex2ctrl() return 1 on success and 0 or a negative value on
220 In particular, the value -2 indicates that the given control type
221 isn't supported by the MAC implementation.
223 EVP_MAC_size() returns the expected output size, or 0 if it isn't
225 If it isn't set, a call to EVP_MAC_init() should get it set.
227 EVP_MAC_nid() returns the numeric identity for the given C<mac>.
229 EVP_MAC_name() returns the name for the given C<mac>, if it has been
230 added to the object database.
232 EVP_add_mac() returns 1 if the given C<mac> was successfully added to
233 the object database, otherwise 0.
235 EVP_get_macbyname(), EVP_get_macbynid() and EVP_get_macbyobj() return
236 the request MAC implementation, if it exists in the object database,
247 #include <openssl/evp.h>
248 #include <openssl/err.h>
250 int ctrl_ign_unsupported(EVP_MAC_CTX *ctx, int cmd, ...)
256 rv = EVP_MAC_vctrl(ctx, cmd, args);
260 rv = 1; /* Ignore unsupported, pretend it worked fine */
267 EVP_get_macbyname(getenv("MY_MAC"));
268 const EVP_CIPHER *cipher =
269 EVP_get_cipherbyname(getenv("MY_MAC_CIPHER"));
270 const EVP_MD *digest =
271 EVP_get_digestbyname(getenv("MY_MAC_DIGEST"));
272 const char *key = getenv("MY_KEY");
273 EVP_MAC_CTX *ctx = NULL;
275 unsigned char buf[4096];
283 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
285 && !ctrl_ign_unsupported(ctx, EVP_MAC_CTRL_SET_CIPHER, cipher))
287 && !ctrl_ign_unsupported(ctx, EVP_MAC_CTRL_SET_MD, digest))
288 || EVP_MAC_ctrl(ctx, EVP_MAC_CTRL_SET_KEY, key, strlen(key)) <= 0)
291 if (!EVP_MAC_init(ctx))
294 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) < 0) {
295 if (!EVP_MAC_update(ctx, buf, read_l))
299 if (!EVP_MAC_final(ctx, buf, &final_l))
303 for (i = 0; i < final_l; i++)
304 printf("%02X", buf[i]);
307 EVP_MAC_CTX_free(ctx);
311 EVP_MAC_CTX_free(ctx);
312 fprintf(stderr, "Something went wrong\n");
313 ERR_print_errors_fp(stderr);
317 A run of this program, called with correct environment variables, can
320 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
321 LD_LIBRARY_PATH=. ./foo < foo.c
322 Result: ECCAAFF041B22A2299EB90A1B53B6D45
324 (in this example, that program was stored in F<foo.c> and compiled to
333 Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
335 Licensed under the OpenSSL license (the "License"). You may not use
336 this file except in compliance with the License. You can obtain a copy
337 in the file LICENSE in the source distribution or at
338 L<https://www.openssl.org/source/license.html>.