Update build for OpenSSL-0.9.8j upgrade.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_f_md.3
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132.\" ========================================================================
133.\"
134.IX Title "BIO_f_md 3"
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135.TH BIO_f_md 3 "2009-01-11" "0.9.8j" "OpenSSL"
136.\" For nroff, turn off justification. Always turn off hyphenation; it makes
137.\" way too many mistakes in technical documents.
138.if n .ad l
139.nh
984263bc 140.SH "NAME"
74dab6c2 141BIO_f_md, BIO_set_md, BIO_get_md, BIO_get_md_ctx \- message digest BIO filter
984263bc 142.SH "SYNOPSIS"
8b0cefbb 143.IX Header "SYNOPSIS"
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144.Vb 2
145\& #include <openssl/bio.h>
146\& #include <openssl/evp.h>
e257b235 147\&
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148\& BIO_METHOD * BIO_f_md(void);
149\& int BIO_set_md(BIO *b,EVP_MD *md);
150\& int BIO_get_md(BIO *b,EVP_MD **mdp);
151\& int BIO_get_md_ctx(BIO *b,EVP_MD_CTX **mdcp);
152.Ve
153.SH "DESCRIPTION"
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154.IX Header "DESCRIPTION"
155\&\fIBIO_f_md()\fR returns the message digest \s-1BIO\s0 method. This is a filter
156\&\s-1BIO\s0 that digests any data passed through it, it is a \s-1BIO\s0 wrapper
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157for the digest routines \fIEVP_DigestInit()\fR, \fIEVP_DigestUpdate()\fR
158and \fIEVP_DigestFinal()\fR.
159.PP
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160Any data written or read through a digest \s-1BIO\s0 using \fIBIO_read()\fR and
161\&\fIBIO_write()\fR is digested.
984263bc 162.PP
8b0cefbb 163\&\fIBIO_gets()\fR, if its \fBsize\fR parameter is large enough finishes the
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164digest calculation and returns the digest value. \fIBIO_puts()\fR is
165not supported.
166.PP
8b0cefbb 167\&\fIBIO_reset()\fR reinitialises a digest \s-1BIO\s0.
984263bc 168.PP
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169\&\fIBIO_set_md()\fR sets the message digest of \s-1BIO\s0 \fBb\fR to \fBmd\fR: this
170must be called to initialize a digest \s-1BIO\s0 before any data is
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171passed through it. It is a \fIBIO_ctrl()\fR macro.
172.PP
8b0cefbb 173\&\fIBIO_get_md()\fR places the a pointer to the digest BIOs digest method
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174in \fBmdp\fR, it is a \fIBIO_ctrl()\fR macro.
175.PP
8b0cefbb 176\&\fIBIO_get_md_ctx()\fR returns the digest BIOs context into \fBmdcp\fR.
984263bc 177.SH "NOTES"
8b0cefbb 178.IX Header "NOTES"
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179The context returned by \fIBIO_get_md_ctx()\fR can be used in calls
180to \fIEVP_DigestFinal()\fR and also the signature routines \fIEVP_SignFinal()\fR
181and \fIEVP_VerifyFinal()\fR.
182.PP
183The context returned by \fIBIO_get_md_ctx()\fR is an internal context
184structure. Changes made to this context will affect the digest
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185\&\s-1BIO\s0 itself and the context pointer will become invalid when the digest
186\&\s-1BIO\s0 is freed.
984263bc 187.PP
8b0cefbb 188After the digest has been retrieved from a digest \s-1BIO\s0 it must be
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189reinitialized by calling \fIBIO_reset()\fR, or \fIBIO_set_md()\fR before any more
190data is passed through it.
191.PP
192If an application needs to call \fIBIO_gets()\fR or \fIBIO_puts()\fR through
193a chain containing digest BIOs then this can be done by prepending
8b0cefbb 194a buffering \s-1BIO\s0.
984263bc 195.SH "RETURN VALUES"
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196.IX Header "RETURN VALUES"
197\&\fIBIO_f_md()\fR returns the digest \s-1BIO\s0 method.
984263bc 198.PP
8b0cefbb 199\&\fIBIO_set_md()\fR, \fIBIO_get_md()\fR and \fIBIO_md_ctx()\fR return 1 for success and
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2000 for failure.
201.SH "EXAMPLES"
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202.IX Header "EXAMPLES"
203The following example creates a \s-1BIO\s0 chain containing an \s-1SHA1\s0 and \s-1MD5\s0
204digest \s-1BIO\s0 and passes the string \*(L"Hello World\*(R" through it. Error
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205checking has been omitted for clarity.
206.PP
e257b235 207.Vb 10
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208\& BIO *bio, *mdtmp;
209\& char message[] = "Hello World";
210\& bio = BIO_new(BIO_s_null());
211\& mdtmp = BIO_new(BIO_f_md());
212\& BIO_set_md(mdtmp, EVP_sha1());
213\& /* For BIO_push() we want to append the sink BIO and keep a note of
214\& * the start of the chain.
215\& */
216\& bio = BIO_push(mdtmp, bio);
217\& mdtmp = BIO_new(BIO_f_md());
218\& BIO_set_md(mdtmp, EVP_md5());
219\& bio = BIO_push(mdtmp, bio);
220\& /* Note: mdtmp can now be discarded */
221\& BIO_write(bio, message, strlen(message));
222.Ve
8b0cefbb 223.PP
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224The next example digests data by reading through a chain instead:
225.PP
e257b235 226.Vb 10
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227\& BIO *bio, *mdtmp;
228\& char buf[1024];
229\& int rdlen;
230\& bio = BIO_new_file(file, "rb");
231\& mdtmp = BIO_new(BIO_f_md());
232\& BIO_set_md(mdtmp, EVP_sha1());
233\& bio = BIO_push(mdtmp, bio);
234\& mdtmp = BIO_new(BIO_f_md());
235\& BIO_set_md(mdtmp, EVP_md5());
236\& bio = BIO_push(mdtmp, bio);
237\& do {
238\& rdlen = BIO_read(bio, buf, sizeof(buf));
239\& /* Might want to do something with the data here */
240\& } while(rdlen > 0);
241.Ve
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242.PP
243This next example retrieves the message digests from a \s-1BIO\s0 chain and
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244outputs them. This could be used with the examples above.
245.PP
e257b235 246.Vb 10
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247\& BIO *mdtmp;
248\& unsigned char mdbuf[EVP_MAX_MD_SIZE];
249\& int mdlen;
250\& int i;
251\& mdtmp = bio; /* Assume bio has previously been set up */
252\& do {
253\& EVP_MD *md;
254\& mdtmp = BIO_find_type(mdtmp, BIO_TYPE_MD);
255\& if(!mdtmp) break;
256\& BIO_get_md(mdtmp, &md);
257\& printf("%s digest", OBJ_nid2sn(EVP_MD_type(md)));
258\& mdlen = BIO_gets(mdtmp, mdbuf, EVP_MAX_MD_SIZE);
259\& for(i = 0; i < mdlen; i++) printf(":%02X", mdbuf[i]);
260\& printf("\en");
261\& mdtmp = BIO_next(mdtmp);
262\& } while(mdtmp);
e257b235 263\&
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264\& BIO_free_all(bio);
265.Ve
266.SH "BUGS"
8b0cefbb 267.IX Header "BUGS"
984263bc 268The lack of support for \fIBIO_puts()\fR and the non standard behaviour of
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269\&\fIBIO_gets()\fR could be regarded as anomalous. It could be argued that \fIBIO_gets()\fR
270and \fIBIO_puts()\fR should be passed to the next \s-1BIO\s0 in the chain and digest
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271the data passed through and that digests should be retrieved using a
272separate \fIBIO_ctrl()\fR call.
273.SH "SEE ALSO"
274.IX Header "SEE ALSO"
8b0cefbb 275\&\s-1TBA\s0