| blob | af33c815432de45238ac19ffce17779c87eaae2e |
1 .\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.20)
2 .\"
3 .\" Standard preamble:
4 .\" ========================================================================
5 .de Sp \" Vertical space (when we can't use .PP)
6 .if t .sp .5v
7 .if n .sp
8 ..
9 .de Vb \" Begin verbatim text
10 .ft CW
11 .nf
12 .ne \\$1
13 ..
14 .de Ve \" End verbatim text
15 .ft R
16 .fi
17 ..
18 .\" Set up some character translations and predefined strings. \*(-- will
19 .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
20 .\" double quote, and \*(R" will give a right double quote. \*(C+ will
21 .\" give a nicer C++. Capital omega is used to do unbreakable dashes and
22 .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
23 .\" nothing in troff, for use with C<>.
24 .tr \(*W-
25 .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
26 .ie n \{\
27 . ds -- \(*W-
28 . ds PI pi
29 . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
30 . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
31 . ds L" ""
32 . ds R" ""
33 . ds C` ""
34 . ds C' ""
35 'br\}
36 .el\{\
37 . ds -- \|\(em\|
38 . ds PI \(*p
39 . ds L" ``
40 . ds R" ''
41 'br\}
42 .\"
43 .\" Escape single quotes in literal strings from groff's Unicode transform.
44 .ie \n(.g .ds Aq \(aq
45 .el .ds Aq '
46 .\"
47 .\" If the F register is turned on, we'll generate index entries on stderr for
48 .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
49 .\" entries marked with X<> in POD. Of course, you'll have to process the
50 .\" output yourself in some meaningful fashion.
51 .ie \nF \{\
52 . de IX
53 . tm Index:\\$1\t\\n%\t"\\$2"
54 ..
55 . nr % 0
56 . rr F
57 .\}
58 .el \{\
59 . de IX
60 ..
61 .\}
62 .\"
63 .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
64 .\" Fear. Run. Save yourself. No user-serviceable parts.
65 . \" fudge factors for nroff and troff
66 .if n \{\
67 . ds #H 0
68 . ds #V .8m
69 . ds #F .3m
70 . ds #[ \f1
71 . ds #] \fP
72 .\}
73 .if t \{\
74 . ds #H ((1u-(\\\\n(.fu%2u))*.13m)
75 . ds #V .6m
76 . ds #F 0
77 . ds #[ \&
78 . ds #] \&
79 .\}
80 . \" simple accents for nroff and troff
81 .if n \{\
82 . ds ' \&
83 . ds ` \&
84 . ds ^ \&
85 . ds , \&
86 . ds ~ ~
87 . ds /
88 .\}
89 .if t \{\
90 . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
91 . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
92 . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
93 . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
94 . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
95 . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
96 .\}
97 . \" troff and (daisy-wheel) nroff accents
98 .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
99 .ds 8 \h'\*(#H'\(*b\h'-\*(#H'
100 .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
101 .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
102 .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
103 .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
104 .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
105 .ds ae a\h'-(\w'a'u*4/10)'e
106 .ds Ae A\h'-(\w'A'u*4/10)'E
107 . \" corrections for vroff
108 .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
109 .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
110 . \" for low resolution devices (crt and lpr)
111 .if \n(.H>23 .if \n(.V>19 \
112 \{\
113 . ds : e
114 . ds 8 ss
115 . ds o a
116 . ds d- d\h'-1'\(ga
117 . ds D- D\h'-1'\(hy
118 . ds th \o'bp'
119 . ds Th \o'LP'
120 . ds ae ae
121 . ds Ae AE
122 .\}
123 .rm #[ #] #H #V #F C
124 .\" ========================================================================
125 .\"
126 .IX Title "BIO_f_md 3"
127 .TH BIO_f_md 3 "2014-04-07" "1.0.1g" "OpenSSL"
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
132 .SH "NAME"
133 BIO_f_md, BIO_set_md, BIO_get_md, BIO_get_md_ctx \- message digest BIO filter
134 .SH "SYNOPSIS"
135 .IX Header "SYNOPSIS"
136 .Vb 2
137 \& #include <openssl/bio.h>
138 \& #include <openssl/evp.h>
139 \&
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"
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
149 for the digest routines \fIEVP_DigestInit()\fR, \fIEVP_DigestUpdate()\fR
150 and \fIEVP_DigestFinal()\fR.
151 .PP
152 Any data written or read through a digest \s-1BIO\s0 using \fIBIO_read()\fR and
153 \&\fIBIO_write()\fR is digested.
154 .PP
155 \&\fIBIO_gets()\fR, if its \fBsize\fR parameter is large enough finishes the
156 digest calculation and returns the digest value. \fIBIO_puts()\fR is
157 not supported.
158 .PP
159 \&\fIBIO_reset()\fR reinitialises a digest \s-1BIO\s0.
160 .PP
161 \&\fIBIO_set_md()\fR sets the message digest of \s-1BIO\s0 \fBb\fR to \fBmd\fR: this
162 must be called to initialize a digest \s-1BIO\s0 before any data is
163 passed through it. It is a \fIBIO_ctrl()\fR macro.
164 .PP
165 \&\fIBIO_get_md()\fR places the a pointer to the digest BIOs digest method
166 in \fBmdp\fR, it is a \fIBIO_ctrl()\fR macro.
167 .PP
168 \&\fIBIO_get_md_ctx()\fR returns the digest BIOs context into \fBmdcp\fR.
169 .SH "NOTES"
170 .IX Header "NOTES"
171 The context returned by \fIBIO_get_md_ctx()\fR can be used in calls
172 to \fIEVP_DigestFinal()\fR and also the signature routines \fIEVP_SignFinal()\fR
173 and \fIEVP_VerifyFinal()\fR.
174 .PP
175 The context returned by \fIBIO_get_md_ctx()\fR is an internal context
176 structure. Changes made to this context will affect the digest
177 \&\s-1BIO\s0 itself and the context pointer will become invalid when the digest
178 \&\s-1BIO\s0 is freed.
179 .PP
180 After the digest has been retrieved from a digest \s-1BIO\s0 it must be
181 reinitialized by calling \fIBIO_reset()\fR, or \fIBIO_set_md()\fR before any more
182 data is passed through it.
183 .PP
184 If an application needs to call \fIBIO_gets()\fR or \fIBIO_puts()\fR through
185 a chain containing digest BIOs then this can be done by prepending
186 a buffering \s-1BIO\s0.
187 .PP
188 Before OpenSSL 1.0.0 the call to \fIBIO_get_md_ctx()\fR would only work if the \s-1BIO\s0
189 had been initialized for example by calling \fIBIO_set_md()\fR ). In OpenSSL
190 1.0.0 and later the context is always returned and the \s-1BIO\s0 is state is set
191 to initialized. This allows applications to initialize the context externally
192 if the standard calls such as \fIBIO_set_md()\fR are not sufficiently flexible.
193 .SH "RETURN VALUES"
194 .IX Header "RETURN VALUES"
195 \&\fIBIO_f_md()\fR returns the digest \s-1BIO\s0 method.
196 .PP
197 \&\fIBIO_set_md()\fR, \fIBIO_get_md()\fR and \fIBIO_md_ctx()\fR return 1 for success and
198 0 for failure.
199 .SH "EXAMPLES"
200 .IX Header "EXAMPLES"
201 The following example creates a \s-1BIO\s0 chain containing an \s-1SHA1\s0 and \s-1MD5\s0
202 digest \s-1BIO\s0 and passes the string \*(L"Hello World\*(R" through it. Error
203 checking has been omitted for clarity.
204 .PP
205 .Vb 10
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
221 .PP
222 The next example digests data by reading through a chain instead:
223 .PP
224 .Vb 10
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
240 .PP
241 This next example retrieves the message digests from a \s-1BIO\s0 chain and
242 outputs them. This could be used with the examples above.
243 .PP
244 .Vb 10
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);
261 \&
262 \& BIO_free_all(bio);
263 .Ve
264 .SH "BUGS"
265 .IX Header "BUGS"
266 The lack of support for \fIBIO_puts()\fR and the non standard behaviour of
267 \&\fIBIO_gets()\fR could be regarded as anomalous. It could be argued that \fIBIO_gets()\fR
268 and \fIBIO_puts()\fR should be passed to the next \s-1BIO\s0 in the chain and digest
269 the data passed through and that digests should be retrieved using a
270 separate \fIBIO_ctrl()\fR call.
271 .SH "SEE ALSO"
272 .IX Header "SEE ALSO"
273 \&\s-1TBA\s0