Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / BIO_f_md.3
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124.\" ========================================================================
125.\"
126.IX Title "BIO_f_md 3"
e3261593 127.TH BIO_f_md 3 "2012-01-04" "1.0.0f" "OpenSSL"
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128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
984263bc 132.SH "NAME"
74dab6c2 133BIO_f_md, BIO_set_md, BIO_get_md, BIO_get_md_ctx \- message digest BIO filter
984263bc 134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 2
137\& #include <openssl/bio.h>
138\& #include <openssl/evp.h>
e257b235 139\&
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140\& BIO_METHOD * BIO_f_md(void);
141\& int BIO_set_md(BIO *b,EVP_MD *md);
142\& int BIO_get_md(BIO *b,EVP_MD **mdp);
143\& int BIO_get_md_ctx(BIO *b,EVP_MD_CTX **mdcp);
144.Ve
145.SH "DESCRIPTION"
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146.IX Header "DESCRIPTION"
147\&\fIBIO_f_md()\fR returns the message digest \s-1BIO\s0 method. This is a filter
148\&\s-1BIO\s0 that digests any data passed through it, it is a \s-1BIO\s0 wrapper
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149for the digest routines \fIEVP_DigestInit()\fR, \fIEVP_DigestUpdate()\fR
150and \fIEVP_DigestFinal()\fR.
151.PP
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152Any data written or read through a digest \s-1BIO\s0 using \fIBIO_read()\fR and
153\&\fIBIO_write()\fR is digested.
984263bc 154.PP
8b0cefbb 155\&\fIBIO_gets()\fR, if its \fBsize\fR parameter is large enough finishes the
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156digest calculation and returns the digest value. \fIBIO_puts()\fR is
157not supported.
158.PP
8b0cefbb 159\&\fIBIO_reset()\fR reinitialises a digest \s-1BIO\s0.
984263bc 160.PP
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161\&\fIBIO_set_md()\fR sets the message digest of \s-1BIO\s0 \fBb\fR to \fBmd\fR: this
162must be called to initialize a digest \s-1BIO\s0 before any data is
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163passed through it. It is a \fIBIO_ctrl()\fR macro.
164.PP
8b0cefbb 165\&\fIBIO_get_md()\fR places the a pointer to the digest BIOs digest method
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166in \fBmdp\fR, it is a \fIBIO_ctrl()\fR macro.
167.PP
8b0cefbb 168\&\fIBIO_get_md_ctx()\fR returns the digest BIOs context into \fBmdcp\fR.
984263bc 169.SH "NOTES"
8b0cefbb 170.IX Header "NOTES"
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171The context returned by \fIBIO_get_md_ctx()\fR can be used in calls
172to \fIEVP_DigestFinal()\fR and also the signature routines \fIEVP_SignFinal()\fR
173and \fIEVP_VerifyFinal()\fR.
174.PP
175The context returned by \fIBIO_get_md_ctx()\fR is an internal context
176structure. Changes made to this context will affect the digest
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177\&\s-1BIO\s0 itself and the context pointer will become invalid when the digest
178\&\s-1BIO\s0 is freed.
984263bc 179.PP
8b0cefbb 180After the digest has been retrieved from a digest \s-1BIO\s0 it must be
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181reinitialized by calling \fIBIO_reset()\fR, or \fIBIO_set_md()\fR before any more
182data is passed through it.
183.PP
184If an application needs to call \fIBIO_gets()\fR or \fIBIO_puts()\fR through
185a chain containing digest BIOs then this can be done by prepending
8b0cefbb 186a buffering \s-1BIO\s0.
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187.PP
188Before OpenSSL 1.0.0 the call to \fIBIO_get_md_ctx()\fR would only work if the \s-1BIO\s0
189had been initialized for example by calling \fIBIO_set_md()\fR ). In OpenSSL
1901.0.0 and later the context is always returned and the \s-1BIO\s0 is state is set
191to initialized. This allows applications to initialize the context externally
192if the standard calls such as \fIBIO_set_md()\fR are not sufficiently flexible.
984263bc 193.SH "RETURN VALUES"
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194.IX Header "RETURN VALUES"
195\&\fIBIO_f_md()\fR returns the digest \s-1BIO\s0 method.
984263bc 196.PP
8b0cefbb 197\&\fIBIO_set_md()\fR, \fIBIO_get_md()\fR and \fIBIO_md_ctx()\fR return 1 for success and
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1980 for failure.
199.SH "EXAMPLES"
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200.IX Header "EXAMPLES"
201The following example creates a \s-1BIO\s0 chain containing an \s-1SHA1\s0 and \s-1MD5\s0
202digest \s-1BIO\s0 and passes the string \*(L"Hello World\*(R" through it. Error
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203checking has been omitted for clarity.
204.PP
e257b235 205.Vb 10
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206\& BIO *bio, *mdtmp;
207\& char message[] = "Hello World";
208\& bio = BIO_new(BIO_s_null());
209\& mdtmp = BIO_new(BIO_f_md());
210\& BIO_set_md(mdtmp, EVP_sha1());
211\& /* For BIO_push() we want to append the sink BIO and keep a note of
212\& * the start of the chain.
213\& */
214\& bio = BIO_push(mdtmp, bio);
215\& mdtmp = BIO_new(BIO_f_md());
216\& BIO_set_md(mdtmp, EVP_md5());
217\& bio = BIO_push(mdtmp, bio);
218\& /* Note: mdtmp can now be discarded */
219\& BIO_write(bio, message, strlen(message));
220.Ve
8b0cefbb 221.PP
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222The next example digests data by reading through a chain instead:
223.PP
e257b235 224.Vb 10
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225\& BIO *bio, *mdtmp;
226\& char buf[1024];
227\& int rdlen;
228\& bio = BIO_new_file(file, "rb");
229\& mdtmp = BIO_new(BIO_f_md());
230\& BIO_set_md(mdtmp, EVP_sha1());
231\& bio = BIO_push(mdtmp, bio);
232\& mdtmp = BIO_new(BIO_f_md());
233\& BIO_set_md(mdtmp, EVP_md5());
234\& bio = BIO_push(mdtmp, bio);
235\& do {
236\& rdlen = BIO_read(bio, buf, sizeof(buf));
237\& /* Might want to do something with the data here */
238\& } while(rdlen > 0);
239.Ve
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240.PP
241This next example retrieves the message digests from a \s-1BIO\s0 chain and
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242outputs them. This could be used with the examples above.
243.PP
e257b235 244.Vb 10
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245\& BIO *mdtmp;
246\& unsigned char mdbuf[EVP_MAX_MD_SIZE];
247\& int mdlen;
248\& int i;
249\& mdtmp = bio; /* Assume bio has previously been set up */
250\& do {
251\& EVP_MD *md;
252\& mdtmp = BIO_find_type(mdtmp, BIO_TYPE_MD);
253\& if(!mdtmp) break;
254\& BIO_get_md(mdtmp, &md);
255\& printf("%s digest", OBJ_nid2sn(EVP_MD_type(md)));
256\& mdlen = BIO_gets(mdtmp, mdbuf, EVP_MAX_MD_SIZE);
257\& for(i = 0; i < mdlen; i++) printf(":%02X", mdbuf[i]);
258\& printf("\en");
259\& mdtmp = BIO_next(mdtmp);
260\& } while(mdtmp);
e257b235 261\&
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262\& BIO_free_all(bio);
263.Ve
264.SH "BUGS"
8b0cefbb 265.IX Header "BUGS"
984263bc 266The lack of support for \fIBIO_puts()\fR and the non standard behaviour of
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267\&\fIBIO_gets()\fR could be regarded as anomalous. It could be argued that \fIBIO_gets()\fR
268and \fIBIO_puts()\fR should be passed to the next \s-1BIO\s0 in the chain and digest
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269the data passed through and that digests should be retrieved using a
270separate \fIBIO_ctrl()\fR call.
271.SH "SEE ALSO"
272.IX Header "SEE ALSO"
8b0cefbb 273\&\s-1TBA\s0