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1 | =pod | ||
2 | |||
3 | =head1 NAME | ||
4 | |||
5 | EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate, | ||
6 | EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE, | ||
7 | EVP_MD_CTX_copy_ex EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size, | ||
8 | EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type, | ||
9 | EVP_md_null, EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_dss, EVP_dss1, EVP_mdc2, | ||
10 | EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj - | ||
11 | EVP digest routines | ||
12 | |||
13 | =head1 SYNOPSIS | ||
14 | |||
15 | #include <openssl/evp.h> | ||
16 | |||
17 | void EVP_MD_CTX_init(EVP_MD_CTX *ctx); | ||
18 | EVP_MD_CTX *EVP_MD_CTX_create(void); | ||
19 | |||
20 | int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); | ||
21 | int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); | ||
22 | int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, | ||
23 | unsigned int *s); | ||
24 | |||
25 | int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx); | ||
26 | void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx); | ||
27 | |||
28 | int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in); | ||
29 | |||
30 | int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type); | ||
31 | int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, | ||
32 | unsigned int *s); | ||
33 | |||
34 | int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in); | ||
35 | |||
36 | #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */ | ||
37 | |||
38 | |||
39 | #define EVP_MD_type(e) ((e)->type) | ||
40 | #define EVP_MD_pkey_type(e) ((e)->pkey_type) | ||
41 | #define EVP_MD_size(e) ((e)->md_size) | ||
42 | #define EVP_MD_block_size(e) ((e)->block_size) | ||
43 | |||
44 | #define EVP_MD_CTX_md(e) (e)->digest) | ||
45 | #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest) | ||
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_sha(void); | ||
53 | const EVP_MD *EVP_sha1(void); | ||
54 | const EVP_MD *EVP_dss(void); | ||
55 | const EVP_MD *EVP_dss1(void); | ||
56 | const EVP_MD *EVP_mdc2(void); | ||
57 | const EVP_MD *EVP_ripemd160(void); | ||
58 | |||
59 | const EVP_MD *EVP_get_digestbyname(const char *name); | ||
60 | #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a)) | ||
61 | #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a)) | ||
62 | |||
63 | =head1 DESCRIPTION | ||
64 | |||
65 | The EVP digest routines are a high level interface to message digests. | ||
66 | |||
67 | EVP_MD_CTX_init() initializes digest contet B<ctx>. | ||
68 | |||
69 | EVP_MD_CTX_create() allocates, initializes and returns a digest contet. | ||
70 | |||
71 | EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest | ||
72 | B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this | ||
73 | function. B<type> will typically be supplied by a functionsuch as EVP_sha1(). | ||
74 | If B<impl> is NULL then the default implementation of digest B<type> is used. | ||
75 | |||
76 | EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the | ||
77 | digest context B<ctx>. This function can be called several times on the | ||
78 | same B<ctx> to hash additional data. | ||
79 | |||
80 | EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places | ||
81 | it in B<md>. If the B<s> parameter is not NULL then the number of | ||
82 | bytes of data written (i.e. the length of the digest) will be written | ||
83 | to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written. | ||
84 | After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate() | ||
85 | can be made, but EVP_DigestInit_ex() can be called to initialize a new | ||
86 | digest operation. | ||
87 | |||
88 | EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called | ||
89 | after a digest context is no longer needed. | ||
90 | |||
91 | EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the | ||
92 | space allocated to it, it should be called only on a context created | ||
93 | using EVP_MD_CTX_create(). | ||
94 | |||
95 | EVP_MD_CTX_copy_ex() can be used to copy the message digest state from | ||
96 | B<in> to B<out>. This is useful if large amounts of data are to be | ||
97 | hashed which only differ in the last few bytes. B<out> must be initialized | ||
98 | before calling this function. | ||
99 | |||
100 | EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except | ||
101 | the passed context B<ctx> does not have to be initialized, and it always | ||
102 | uses the default digest implementation. | ||
103 | |||
104 | EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest | ||
105 | contet B<ctx> is automatically cleaned up. | ||
106 | |||
107 | EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination | ||
108 | B<out> does not have to be initialized. | ||
109 | |||
110 | EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest | ||
111 | when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the | ||
112 | hash. | ||
113 | |||
114 | EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the | ||
115 | message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure. | ||
116 | |||
117 | EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER | ||
118 | representing the given message digest when passed an B<EVP_MD> structure. | ||
119 | For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is | ||
120 | normally used when setting ASN1 OIDs. | ||
121 | |||
122 | EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed | ||
123 | B<EVP_MD_CTX>. | ||
124 | |||
125 | EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated | ||
126 | with this digest. For example EVP_sha1() is associated with RSA so this will | ||
127 | return B<NID_sha1WithRSAEncryption>. This "link" between digests and signature | ||
128 | algorithms may not be retained in future versions of OpenSSL. | ||
129 | |||
130 | EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and EVP_ripemd160() | ||
131 | return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest | ||
132 | algorithms respectively. The associated signature algorithm is RSA in each case. | ||
133 | |||
134 | EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest | ||
135 | algorithms but using DSS (DSA) for the signature algorithm. | ||
136 | |||
137 | EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it | ||
138 | returns is of zero length. | ||
139 | |||
140 | EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() | ||
141 | return an B<EVP_MD> structure when passed a digest name, a digest NID or | ||
142 | an ASN1_OBJECT structure respectively. The digest table must be initialized | ||
143 | using, for example, OpenSSL_add_all_digests() for these functions to work. | ||
144 | |||
145 | =head1 RETURN VALUES | ||
146 | |||
147 | EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for | ||
148 | success and 0 for failure. | ||
149 | |||
150 | EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure. | ||
151 | |||
152 | EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the | ||
153 | corresponding OBJECT IDENTIFIER or NID_undef if none exists. | ||
154 | |||
155 | EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e), EVP_MD_size(), | ||
156 | EVP_MD_CTX_block_size() and EVP_MD_block_size() return the digest or block | ||
157 | size in bytes. | ||
158 | |||
159 | EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(), | ||
160 | EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the | ||
161 | corresponding EVP_MD structures. | ||
162 | |||
163 | EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() | ||
164 | return either an B<EVP_MD> structure or NULL if an error occurs. | ||
165 | |||
166 | =head1 NOTES | ||
167 | |||
168 | The B<EVP> interface to message digests should almost always be used in | ||
169 | preference to the low level interfaces. This is because the code then becomes | ||
170 | transparent to the digest used and much more flexible. | ||
171 | |||
172 | SHA1 is the digest of choice for new applications. The other digest algorithms | ||
173 | are still in common use. | ||
174 | |||
175 | For most applications the B<impl> parameter to EVP_DigestInit_ex() will be | ||
176 | set to NULL to use the default digest implementation. | ||
177 | |||
178 | The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are | ||
179 | obsolete but are retained to maintain compatibility with existing code. New | ||
180 | applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and | ||
181 | EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context | ||
182 | instead of initializing and cleaning it up on each call and allow non default | ||
183 | implementations of digests to be specified. | ||
184 | |||
185 | In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use | ||
186 | memory leaks will occur. | ||
187 | |||
188 | =head1 EXAMPLE | ||
189 | |||
190 | This example digests the data "Test Message\n" and "Hello World\n", using the | ||
191 | digest name passed on the command line. | ||
192 | |||
193 | #include <stdio.h> | ||
194 | #include <openssl/evp.h> | ||
195 | |||
196 | main(int argc, char *argv[]) | ||
197 | { | ||
198 | EVP_MD_CTX mdctx; | ||
199 | const EVP_MD *md; | ||
200 | char mess1[] = "Test Message\n"; | ||
201 | char mess2[] = "Hello World\n"; | ||
202 | unsigned char md_value[EVP_MAX_MD_SIZE]; | ||
203 | int md_len, i; | ||
204 | |||
205 | OpenSSL_add_all_digests(); | ||
206 | |||
207 | if(!argv[1]) { | ||
208 | printf("Usage: mdtest digestname\n"); | ||
209 | exit(1); | ||
210 | } | ||
211 | |||
212 | md = EVP_get_digestbyname(argv[1]); | ||
213 | |||
214 | if(!md) { | ||
215 | printf("Unknown message digest %s\n", argv[1]); | ||
216 | exit(1); | ||
217 | } | ||
218 | |||
219 | EVP_MD_CTX_init(&mdctx); | ||
220 | EVP_DigestInit_ex(&mdctx, md, NULL); | ||
221 | EVP_DigestUpdate(&mdctx, mess1, strlen(mess1)); | ||
222 | EVP_DigestUpdate(&mdctx, mess2, strlen(mess2)); | ||
223 | EVP_DigestFinal_ex(&mdctx, md_value, &md_len); | ||
224 | EVP_MD_CTX_cleanup(&mdctx); | ||
225 | |||
226 | printf("Digest is: "); | ||
227 | for(i = 0; i < md_len; i++) printf("%02x", md_value[i]); | ||
228 | printf("\n"); | ||
229 | } | ||
230 | |||
231 | =head1 BUGS | ||
232 | |||
233 | The link between digests and signing algorithms results in a situation where | ||
234 | EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS | ||
235 | even though they are identical digests. | ||
236 | |||
237 | =head1 SEE ALSO | ||
238 | |||
239 | L<evp(3)|evp(3)>, L<HMAC(3)|HMAC(3)>, L<MD2(3)|MD2(3)>, | ||
240 | L<MD5(3)|MD5(3)>, L<MDC2(3)|MDC2(3)>, L<RIPEMD160(3)|RIPEMD160(3)>, | ||
241 | L<SHA1(3)|SHA1(3)> | ||
242 | |||
243 | =head1 HISTORY | ||
244 | |||
245 | EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are | ||
246 | available in all versions of SSLeay and OpenSSL. | ||
247 | |||
248 | EVP_MD_CTX_init(), EVP_MD_CTX_create(), EVP_MD_CTX_copy_ex(), | ||
249 | EVP_MD_CTX_cleanup(), EVP_MD_CTX_destroy(), EVP_DigestInit_ex() | ||
250 | and EVP_DigestFinal_ex() were added in OpenSSL 0.9.7. | ||
251 | |||
252 | EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), | ||
253 | EVP_dss(), EVP_dss1(), EVP_mdc2() and EVP_ripemd160() were | ||
254 | changed to return truely const EVP_MD * in OpenSSL 0.9.7. | ||
255 | |||
256 | =cut | ||