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authorschwarze <>2016-11-03 09:35:34 +0000
committerschwarze <>2016-11-03 09:35:34 +0000
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convert EVP manuals from pod to mdoc
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1=pod
2
3=head1 NAME
4
5EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate,
6EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE,
7EVP_MD_CTX_copy_ex, EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type,
8EVP_MD_size, EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size,
9EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_md_null, EVP_md2, EVP_md5,
10EVP_sha1, EVP_sha224, EVP_sha256, EVP_sha384, EVP_sha512, EVP_dss, EVP_dss1,
11EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid,
12EVP_get_digestbyobj, EVP_DigestInit, EVP_DigestFinal - EVP digest routines
13
14=head1 SYNOPSIS
15
16 #include <openssl/evp.h>
17
18 void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
19 EVP_MD_CTX *EVP_MD_CTX_create(void);
20
21 int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
22 int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
23 int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
24 unsigned int *s);
25
26 int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
27 void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);
28
29 int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);
30
31 int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
32 int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
33 unsigned int *s);
34
35 int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);
36
37 #define EVP_MAX_MD_SIZE 64 /* SHA512 */
38
39 int EVP_MD_type(const EVP_MD *md);
40 int EVP_MD_pkey_type(const EVP_MD *md);
41 int EVP_MD_size(const EVP_MD *md);
42 int EVP_MD_block_size(const EVP_MD *md);
43
44 const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
45 #define EVP_MD_CTX_size(e) EVP_MD_size(EVP_MD_CTX_md(e))
46 #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest)
47 #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest)
48
49 const EVP_MD *EVP_md_null(void);
50 const EVP_MD *EVP_md2(void);
51 const EVP_MD *EVP_md5(void);
52 const EVP_MD *EVP_sha1(void);
53 const EVP_MD *EVP_dss(void);
54 const EVP_MD *EVP_dss1(void);
55 const EVP_MD *EVP_ripemd160(void);
56
57 const EVP_MD *EVP_sha224(void);
58 const EVP_MD *EVP_sha256(void);
59 const EVP_MD *EVP_sha384(void);
60 const EVP_MD *EVP_sha512(void);
61
62 const EVP_MD *EVP_get_digestbyname(const char *name);
63 #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
64 #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))
65
66=head1 DESCRIPTION
67
68The EVP digest routines are a high level interface to message digests.
69
70EVP_MD_CTX_init() initializes digest context B<ctx>.
71
72EVP_MD_CTX_create() allocates, initializes and returns a digest context.
73
74EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest
75B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this
76function. B<type> will typically be supplied by a function such as EVP_sha1().
77If B<impl> is NULL then the default implementation of digest B<type> is used.
78
79EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the
80digest context B<ctx>. This function can be called several times on the
81same B<ctx> to hash additional data.
82
83EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places
84it in B<md>. If the B<s> parameter is not NULL then the number of
85bytes of data written (i.e. the length of the digest) will be written
86to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.
87After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate()
88can be made, but EVP_DigestInit_ex() can be called to initialize a new
89digest operation.
90
91EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called
92after a digest context is no longer needed.
93
94EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the
95space allocated to it, it should be called only on a context created
96using EVP_MD_CTX_create().
97
98EVP_MD_CTX_copy_ex() can be used to copy the message digest state from
99B<in> to B<out>. This is useful if large amounts of data are to be
100hashed which only differ in the last few bytes. B<out> must be initialized
101before calling this function.
102
103EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except
104the passed context B<ctx> does not have to be initialized, and it always
105uses the default digest implementation.
106
107EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest
108context B<ctx> is automatically cleaned up.
109
110EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination
111B<out> does not have to be initialized.
112
113EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest
114when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the
115hash.
116
117EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the
118message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure.
119
120EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER
121representing the given message digest when passed an B<EVP_MD> structure.
122For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is
123normally used when setting ASN1 OIDs.
124
125EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed
126B<EVP_MD_CTX>.
127
128EVP_MD_pkey_type() returns the NID of the public key signing algorithm
129associated with this digest. For example EVP_sha1() is associated with RSA so
130this will return B<NID_sha1WithRSAEncryption>. Since digests and signature
131algorithms are no longer linked this function is only retained for
132compatibility reasons.
133
134EVP_md2(), EVP_md5(), EVP_sha1(), EVP_sha224(), EVP_sha256(), EVP_sha384(),
135EVP_sha512() and EVP_ripemd160() return B<EVP_MD> structures for the MD2, MD5,
136SHA1, SHA224, SHA256, SHA384, SHA512 and RIPEMD160 digest algorithms
137respectively.
138
139EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA1 digest
140algorithms but using DSS (DSA) for the signature algorithm. Note: there is
141no need to use these pseudo-digests in OpenSSL 1.0.0 and later, they are
142however retained for compatibility.
143
144EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it
145returns is of zero length.
146
147EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
148return an B<EVP_MD> structure when passed a digest name, a digest NID or
149an ASN1_OBJECT structure respectively. The digest table must be initialized
150using, for example, OpenSSL_add_all_digests() for these functions to work.
151
152=head1 RETURN VALUES
153
154EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for
155success and 0 for failure.
156
157EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure.
158
159EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the
160corresponding OBJECT IDENTIFIER or NID_undef if none exists.
161
162EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size() and
163EVP_MD_CTX_block_size() return the digest or block size in bytes.
164
165EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha1(), EVP_dss(),
166EVP_dss1() and EVP_ripemd160() return pointers to the
167corresponding EVP_MD structures.
168
169EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
170return either an B<EVP_MD> structure or NULL if an error occurs.
171
172=head1 NOTES
173
174The B<EVP> interface to message digests should almost always be used in
175preference to the low level interfaces. This is because the code then becomes
176transparent to the digest used and much more flexible.
177
178New applications should use the SHA2 digest algorithms such as SHA256.
179The other digest algorithms are still in common use.
180
181For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
182set to NULL to use the default digest implementation.
183
184The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are
185obsolete but are retained to maintain compatibility with existing code. New
186applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
187EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
188instead of initializing and cleaning it up on each call and allow non default
189implementations of digests to be specified.
190
191In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use
192memory leaks will occur.
193
194Stack allocation of EVP_MD_CTX structures is common, for example:
195
196 EVP_MD_CTX mctx;
197 EVP_MD_CTX_init(&mctx);
198
199This will cause binary compatibility issues if the size of EVP_MD_CTX
200structure changes (this will only happen with a major release of OpenSSL).
201Applications wishing to avoid this should use EVP_MD_CTX_create() instead:
202
203 EVP_MD_CTX *mctx;
204 mctx = EVP_MD_CTX_create();
205
206
207=head1 EXAMPLE
208
209This example digests the data "Test Message\n" and "Hello World\n", using the
210digest name passed on the command line.
211
212 #include <stdio.h>
213 #include <openssl/evp.h>
214
215 int
216 main(int argc, char *argv[])
217 {
218 EVP_MD_CTX *mdctx;
219 const EVP_MD *md;
220 const char mess1[] = "Test Message\n";
221 const char mess2[] = "Hello World\n";
222 unsigned char md_value[EVP_MAX_MD_SIZE];
223 int md_len, i;
224
225 OpenSSL_add_all_digests();
226
227 if (argc <= 1) {
228 printf("Usage: mdtest digestname\n");
229 exit(1);
230 }
231
232 md = EVP_get_digestbyname(argv[1]);
233 if (md == NULL) {
234 printf("Unknown message digest %s\n", argv[1]);
235 exit(1);
236 }
237
238 mdctx = EVP_MD_CTX_create();
239 EVP_DigestInit_ex(mdctx, md, NULL);
240 EVP_DigestUpdate(mdctx, mess1, strlen(mess1));
241 EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
242 EVP_DigestFinal_ex(mdctx, md_value, &md_len);
243 EVP_MD_CTX_destroy(mdctx);
244
245 printf("Digest is: ");
246 for(i = 0; i < md_len; i++)
247 printf("%02x", md_value[i]);
248 printf("\n");
249 }
250
251=head1 SEE ALSO
252
253L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
254L<md5(3)|md5(3)>, L<ripemd(3)|ripemd(3)>,
255L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)>
256
257=head1 HISTORY
258
259EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are
260available in all versions of SSLeay and OpenSSL.
261
262EVP_MD_CTX_init(), EVP_MD_CTX_create(), EVP_MD_CTX_copy_ex(),
263EVP_MD_CTX_cleanup(), EVP_MD_CTX_destroy(), EVP_DigestInit_ex()
264and EVP_DigestFinal_ex() were added in OpenSSL 0.9.7.
265
266EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha1(),
267EVP_dss(), EVP_dss1() and EVP_ripemd160() were
268changed to return truely const EVP_MD * in OpenSSL 0.9.7.
269
270The link between digests and signing algorithms was fixed in OpenSSL 1.0 and
271later, so now EVP_sha1() can be used with RSA and DSA, there is no need to
272use EVP_dss1() any more.
273
274OpenSSL 1.0 and later does not include the MD2 digest algorithm in the
275default configuration due to its security weaknesses.
276
277=cut