Switch from OpenSSL 0.9.7a to OpenSSL 0.9.7d.
[dragonfly.git] / secure / lib / libcrypto / man / EVP_DigestInit.3
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138.\" ======================================================================
139.\"
140.IX Title "EVP_DigestInit 3"
141.TH EVP_DigestInit 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate,
145EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, \s-1EVP_MAX_MD_SIZE\s0,
146EVP_MD_CTX_copy_ex EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size,
147EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type,
148EVP_md_null, EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_dss, EVP_dss1, EVP_mdc2,
149EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj \-
150\&\s-1EVP\s0 digest routines
151.SH "SYNOPSIS"
152.IX Header "SYNOPSIS"
153.Vb 1
154\& #include <openssl/evp.h>
155.Ve
156.Vb 2
157\& void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
158\& EVP_MD_CTX *EVP_MD_CTX_create(void);
159.Ve
160.Vb 4
161\& int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
162\& int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
163\& int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
164\& unsigned int *s);
165.Ve
166.Vb 2
167\& int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
168\& void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);
169.Ve
170.Vb 1
171\& int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);
172.Ve
173.Vb 3
174\& int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
175\& int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
176\& unsigned int *s);
177.Ve
178.Vb 1
179\& int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);
180.Ve
181.Vb 1
182\& #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
183.Ve
184.Vb 4
185\& #define EVP_MD_type(e) ((e)->type)
186\& #define EVP_MD_pkey_type(e) ((e)->pkey_type)
187\& #define EVP_MD_size(e) ((e)->md_size)
188\& #define EVP_MD_block_size(e) ((e)->block_size)
189.Ve
190.Vb 4
191\& #define EVP_MD_CTX_md(e) (e)->digest)
192\& #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest)
193\& #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest)
194\& #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest)
195.Ve
196.Vb 9
197\& const EVP_MD *EVP_md_null(void);
198\& const EVP_MD *EVP_md2(void);
199\& const EVP_MD *EVP_md5(void);
200\& const EVP_MD *EVP_sha(void);
201\& const EVP_MD *EVP_sha1(void);
202\& const EVP_MD *EVP_dss(void);
203\& const EVP_MD *EVP_dss1(void);
204\& const EVP_MD *EVP_mdc2(void);
205\& const EVP_MD *EVP_ripemd160(void);
206.Ve
207.Vb 3
208\& const EVP_MD *EVP_get_digestbyname(const char *name);
209\& #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
210\& #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))
211.Ve
212.SH "DESCRIPTION"
213.IX Header "DESCRIPTION"
214The \s-1EVP\s0 digest routines are a high level interface to message digests.
215.PP
216\&\fIEVP_MD_CTX_init()\fR initializes digest contet \fBctx\fR.
217.PP
218\&\fIEVP_MD_CTX_create()\fR allocates, initializes and returns a digest contet.
219.PP
220\&\fIEVP_DigestInit_ex()\fR sets up digest context \fBctx\fR to use a digest
221\&\fBtype\fR from \s-1ENGINE\s0 \fBimpl\fR. \fBctx\fR must be initialized before calling this
222function. \fBtype\fR will typically be supplied by a functionsuch as \fIEVP_sha1()\fR.
223If \fBimpl\fR is \s-1NULL\s0 then the default implementation of digest \fBtype\fR is used.
224.PP
225\&\fIEVP_DigestUpdate()\fR hashes \fBcnt\fR bytes of data at \fBd\fR into the
226digest context \fBctx\fR. This function can be called several times on the
227same \fBctx\fR to hash additional data.
228.PP
229\&\fIEVP_DigestFinal_ex()\fR retrieves the digest value from \fBctx\fR and places
230it in \fBmd\fR. If the \fBs\fR parameter is not \s-1NULL\s0 then the number of
231bytes of data written (i.e. the length of the digest) will be written
232to the integer at \fBs\fR, at most \fB\s-1EVP_MAX_MD_SIZE\s0\fR bytes will be written.
233After calling \fIEVP_DigestFinal_ex()\fR no additional calls to \fIEVP_DigestUpdate()\fR
234can be made, but \fIEVP_DigestInit_ex()\fR can be called to initialize a new
235digest operation.
236.PP
237\&\fIEVP_MD_CTX_cleanup()\fR cleans up digest context \fBctx\fR, it should be called
238after a digest context is no longer needed.
239.PP
240\&\fIEVP_MD_CTX_destroy()\fR cleans up digest context \fBctx\fR and frees up the
241space allocated to it, it should be called only on a context created
242using \fIEVP_MD_CTX_create()\fR.
243.PP
244\&\fIEVP_MD_CTX_copy_ex()\fR can be used to copy the message digest state from
245\&\fBin\fR to \fBout\fR. This is useful if large amounts of data are to be
246hashed which only differ in the last few bytes. \fBout\fR must be initialized
247before calling this function.
248.PP
249\&\fIEVP_DigestInit()\fR behaves in the same way as \fIEVP_DigestInit_ex()\fR except
250the passed context \fBctx\fR does not have to be initialized, and it always
251uses the default digest implementation.
252.PP
253\&\fIEVP_DigestFinal()\fR is similar to \fIEVP_DigestFinal_ex()\fR except the digest
254contet \fBctx\fR is automatically cleaned up.
255.PP
256\&\fIEVP_MD_CTX_copy()\fR is similar to \fIEVP_MD_CTX_copy_ex()\fR except the destination
257\&\fBout\fR does not have to be initialized.
258.PP
259\&\fIEVP_MD_size()\fR and \fIEVP_MD_CTX_size()\fR return the size of the message digest
260when passed an \fB\s-1EVP_MD\s0\fR or an \fB\s-1EVP_MD_CTX\s0\fR structure, i.e. the size of the
261hash.
262.PP
263\&\fIEVP_MD_block_size()\fR and \fIEVP_MD_CTX_block_size()\fR return the block size of the
264message digest when passed an \fB\s-1EVP_MD\s0\fR or an \fB\s-1EVP_MD_CTX\s0\fR structure.
265.PP
266\&\fIEVP_MD_type()\fR and \fIEVP_MD_CTX_type()\fR return the \s-1NID\s0 of the \s-1OBJECT\s0 \s-1IDENTIFIER\s0
267representing the given message digest when passed an \fB\s-1EVP_MD\s0\fR structure.
268For example EVP_MD_type(\fIEVP_sha1()\fR) returns \fBNID_sha1\fR. This function is
269normally used when setting \s-1ASN1\s0 OIDs.
270.PP
271\&\fIEVP_MD_CTX_md()\fR returns the \fB\s-1EVP_MD\s0\fR structure corresponding to the passed
272\&\fB\s-1EVP_MD_CTX\s0\fR.
273.PP
274\&\fIEVP_MD_pkey_type()\fR returns the \s-1NID\s0 of the public key signing algorithm associated
275with this digest. For example \fIEVP_sha1()\fR is associated with \s-1RSA\s0 so this will
276return \fBNID_sha1WithRSAEncryption\fR. This \*(L"link\*(R" between digests and signature
277algorithms may not be retained in future versions of OpenSSL.
278.PP
279\&\fIEVP_md2()\fR, \fIEVP_md5()\fR, \fIEVP_sha()\fR, \fIEVP_sha1()\fR, \fIEVP_mdc2()\fR and \fIEVP_ripemd160()\fR
280return \fB\s-1EVP_MD\s0\fR structures for the \s-1MD2\s0, \s-1MD5\s0, \s-1SHA\s0, \s-1SHA1\s0, \s-1MDC2\s0 and \s-1RIPEMD160\s0 digest
281algorithms respectively. The associated signature algorithm is \s-1RSA\s0 in each case.
282.PP
283\&\fIEVP_dss()\fR and \fIEVP_dss1()\fR return \fB\s-1EVP_MD\s0\fR structures for \s-1SHA\s0 and \s-1SHA1\s0 digest
284algorithms but using \s-1DSS\s0 (\s-1DSA\s0) for the signature algorithm.
285.PP
286\&\fIEVP_md_null()\fR is a \*(L"null\*(R" message digest that does nothing: i.e. the hash it
287returns is of zero length.
288.PP
289\&\fIEVP_get_digestbyname()\fR, \fIEVP_get_digestbynid()\fR and \fIEVP_get_digestbyobj()\fR
290return an \fB\s-1EVP_MD\s0\fR structure when passed a digest name, a digest \s-1NID\s0 or
291an \s-1ASN1_OBJECT\s0 structure respectively. The digest table must be initialized
292using, for example, \fIOpenSSL_add_all_digests()\fR for these functions to work.
293.SH "RETURN VALUES"
294.IX Header "RETURN VALUES"
295\&\fIEVP_DigestInit_ex()\fR, \fIEVP_DigestUpdate()\fR and \fIEVP_DigestFinal_ex()\fR return 1 for
296success and 0 for failure.
297.PP
298\&\fIEVP_MD_CTX_copy_ex()\fR returns 1 if successful or 0 for failure.
299.PP
300\&\fIEVP_MD_type()\fR, \fIEVP_MD_pkey_type()\fR and \fIEVP_MD_type()\fR return the \s-1NID\s0 of the
301corresponding \s-1OBJECT\s0 \s-1IDENTIFIER\s0 or NID_undef if none exists.
302.PP
303\&\fIEVP_MD_size()\fR, \fIEVP_MD_block_size()\fR, \fIEVP_MD_CTX_size\fR\|(e), \fIEVP_MD_size()\fR,
304\&\fIEVP_MD_CTX_block_size()\fR and \fIEVP_MD_block_size()\fR return the digest or block
305size in bytes.
306.PP
307\&\fIEVP_md_null()\fR, \fIEVP_md2()\fR, \fIEVP_md5()\fR, \fIEVP_sha()\fR, \fIEVP_sha1()\fR, \fIEVP_dss()\fR,
308\&\fIEVP_dss1()\fR, \fIEVP_mdc2()\fR and \fIEVP_ripemd160()\fR return pointers to the
309corresponding \s-1EVP_MD\s0 structures.
310.PP
311\&\fIEVP_get_digestbyname()\fR, \fIEVP_get_digestbynid()\fR and \fIEVP_get_digestbyobj()\fR
312return either an \fB\s-1EVP_MD\s0\fR structure or \s-1NULL\s0 if an error occurs.
313.SH "NOTES"
314.IX Header "NOTES"
315The \fB\s-1EVP\s0\fR interface to message digests should almost always be used in
316preference to the low level interfaces. This is because the code then becomes
317transparent to the digest used and much more flexible.
318.PP
319\&\s-1SHA1\s0 is the digest of choice for new applications. The other digest algorithms
320are still in common use.
321.PP
322For most applications the \fBimpl\fR parameter to \fIEVP_DigestInit_ex()\fR will be
323set to \s-1NULL\s0 to use the default digest implementation.
324.PP
325The functions \fIEVP_DigestInit()\fR, \fIEVP_DigestFinal()\fR and \fIEVP_MD_CTX_copy()\fR are
326obsolete but are retained to maintain compatibility with existing code. New
327applications should use \fIEVP_DigestInit_ex()\fR, \fIEVP_DigestFinal_ex()\fR and
328\&\fIEVP_MD_CTX_copy_ex()\fR because they can efficiently reuse a digest context
329instead of initializing and cleaning it up on each call and allow non default
330implementations of digests to be specified.
331.PP
332In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use
333memory leaks will occur.
334.SH "EXAMPLE"
335.IX Header "EXAMPLE"
336This example digests the data \*(L"Test Message\en\*(R" and \*(L"Hello World\en\*(R", using the
337digest name passed on the command line.
338.PP
339.Vb 2
340\& #include <stdio.h>
341\& #include <openssl/evp.h>
342.Ve
343.Vb 8
344\& main(int argc, char *argv[])
345\& {
346\& EVP_MD_CTX mdctx;
347\& const EVP_MD *md;
348\& char mess1[] = "Test Message\en";
349\& char mess2[] = "Hello World\en";
350\& unsigned char md_value[EVP_MAX_MD_SIZE];
351\& int md_len, i;
352.Ve
353.Vb 1
354\& OpenSSL_add_all_digests();
355.Ve
356.Vb 4
357\& if(!argv[1]) {
358\& printf("Usage: mdtest digestname\en");
359\& exit(1);
360\& }
361.Ve
362.Vb 1
363\& md = EVP_get_digestbyname(argv[1]);
364.Ve
365.Vb 4
366\& if(!md) {
367\& printf("Unknown message digest %s\en", argv[1]);
368\& exit(1);
369\& }
370.Ve
371.Vb 6
372\& EVP_MD_CTX_init(&mdctx);
373\& EVP_DigestInit_ex(&mdctx, md, NULL);
374\& EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
375\& EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
376\& EVP_DigestFinal_ex(&mdctx, md_value, &md_len);
377\& EVP_MD_CTX_cleanup(&mdctx);
378.Ve
379.Vb 4
380\& printf("Digest is: ");
381\& for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
382\& printf("\en");
383\& }
384.Ve
385.SH "BUGS"
386.IX Header "BUGS"
387The link between digests and signing algorithms results in a situation where
388\&\fIEVP_sha1()\fR must be used with \s-1RSA\s0 and \fIEVP_dss1()\fR must be used with \s-1DSS\s0
389even though they are identical digests.
390.SH "SEE ALSO"
391.IX Header "SEE ALSO"
392evp(3), hmac(3), md2(3),
393md5(3), mdc2(3), ripemd(3),
394sha(3), dgst(1)
395.SH "HISTORY"
396.IX Header "HISTORY"
397\&\fIEVP_DigestInit()\fR, \fIEVP_DigestUpdate()\fR and \fIEVP_DigestFinal()\fR are
398available in all versions of SSLeay and OpenSSL.
399.PP
400\&\fIEVP_MD_CTX_init()\fR, \fIEVP_MD_CTX_create()\fR, \fIEVP_MD_CTX_copy_ex()\fR,
401\&\fIEVP_MD_CTX_cleanup()\fR, \fIEVP_MD_CTX_destroy()\fR, \fIEVP_DigestInit_ex()\fR
402and \fIEVP_DigestFinal_ex()\fR were added in OpenSSL 0.9.7.
403.PP
404\&\fIEVP_md_null()\fR, \fIEVP_md2()\fR, \fIEVP_md5()\fR, \fIEVP_sha()\fR, \fIEVP_sha1()\fR,
405\&\fIEVP_dss()\fR, \fIEVP_dss1()\fR, \fIEVP_mdc2()\fR and \fIEVP_ripemd160()\fR were
406changed to return truely const \s-1EVP_MD\s0 * in OpenSSL 0.9.7.