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124 .\" ========================================================================
126 .IX Title "d2i_X509 3"
127 .TH d2i_X509 3 "2012-05-10" "1.0.1c" "OpenSSL"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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133 d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio,
134 i2d_X509_fp \- X509 encode and decode functions
136 .IX Header "SYNOPSIS"
138 \& #include <openssl/x509.h>
140 \& X509 *d2i_X509(X509 **px, const unsigned char **in, int len);
141 \& int i2d_X509(X509 *x, unsigned char **out);
143 \& X509 *d2i_X509_bio(BIO *bp, X509 **x);
144 \& X509 *d2i_X509_fp(FILE *fp, X509 **x);
146 \& int i2d_X509_bio(BIO *bp, X509 *x);
147 \& int i2d_X509_fp(FILE *fp, X509 *x);
150 .IX Header "DESCRIPTION"
151 The X509 encode and decode routines encode and parse an
152 \&\fBX509\fR structure, which represents an X509 certificate.
154 \&\fId2i_X509()\fR attempts to decode \fBlen\fR bytes at \fB*in\fR. If
155 successful a pointer to the \fBX509\fR structure is returned. If an error
156 occurred then \fB\s-1NULL\s0\fR is returned. If \fBpx\fR is not \fB\s-1NULL\s0\fR then the
157 returned structure is written to \fB*px\fR. If \fB*px\fR is not \fB\s-1NULL\s0\fR
158 then it is assumed that \fB*px\fR contains a valid \fBX509\fR
159 structure and an attempt is made to reuse it. If the call is
160 successful \fB*in\fR is incremented to the byte following the
163 \&\fIi2d_X509()\fR encodes the structure pointed to by \fBx\fR into \s-1DER\s0 format.
164 If \fBout\fR is not \fB\s-1NULL\s0\fR is writes the \s-1DER\s0 encoded data to the buffer
165 at \fB*out\fR, and increments it to point after the data just written.
166 If the return value is negative an error occurred, otherwise it
167 returns the length of the encoded data.
169 For OpenSSL 0.9.7 and later if \fB*out\fR is \fB\s-1NULL\s0\fR memory will be
170 allocated for a buffer and the encoded data written to it. In this
171 case \fB*out\fR is not incremented and it points to the start of the
174 \&\fId2i_X509_bio()\fR is similar to \fId2i_X509()\fR except it attempts
175 to parse data from \s-1BIO\s0 \fBbp\fR.
177 \&\fId2i_X509_fp()\fR is similar to \fId2i_X509()\fR except it attempts
178 to parse data from \s-1FILE\s0 pointer \fBfp\fR.
180 \&\fIi2d_X509_bio()\fR is similar to \fIi2d_X509()\fR except it writes
181 the encoding of the structure \fBx\fR to \s-1BIO\s0 \fBbp\fR and it
182 returns 1 for success and 0 for failure.
184 \&\fIi2d_X509_fp()\fR is similar to \fIi2d_X509()\fR except it writes
185 the encoding of the structure \fBx\fR to \s-1BIO\s0 \fBbp\fR and it
186 returns 1 for success and 0 for failure.
189 The letters \fBi\fR and \fBd\fR in for example \fBi2d_X509\fR stand for
190 \&\*(L"internal\*(R" (that is an internal C structure) and \*(L"\s-1DER\s0\*(R". So that
191 \&\fBi2d_X509\fR converts from internal to \s-1DER\s0.
193 The functions can also understand \fB\s-1BER\s0\fR forms.
195 The actual X509 structure passed to \fIi2d_X509()\fR must be a valid
196 populated \fBX509\fR structure it can \fBnot\fR simply be fed with an
197 empty structure such as that returned by \fIX509_new()\fR.
199 The encoded data is in binary form and may contain embedded zeroes.
200 Therefore any \s-1FILE\s0 pointers or BIOs should be opened in binary mode.
201 Functions such as \fB\f(BIstrlen()\fB\fR will \fBnot\fR return the correct length
202 of the encoded structure.
204 The ways that \fB*in\fR and \fB*out\fR are incremented after the operation
205 can trap the unwary. See the \fB\s-1WARNINGS\s0\fR section for some common
208 The reason for the auto increment behaviour is to reflect a typical
209 usage of \s-1ASN1\s0 functions: after one structure is encoded or decoded
210 another will processed after it.
212 .IX Header "EXAMPLES"
213 Allocate and encode the \s-1DER\s0 encoding of an X509 structure:
217 \& unsigned char *buf, *p;
219 \& len = i2d_X509(x, NULL);
221 \& buf = OPENSSL_malloc(len);
231 If you are using OpenSSL 0.9.7 or later then this can be
236 \& unsigned char *buf;
240 \& len = i2d_X509(x, &buf);
246 Attempt to decode a buffer:
251 \& unsigned char *buf, *p;
255 \& /* Something to setup buf and len */
259 \& x = d2i_X509(NULL, &p, len);
265 Alternative technique:
270 \& unsigned char *buf, *p;
274 \& /* Something to setup buf and len */
280 \& if(!d2i_X509(&x, &p, len))
284 .IX Header "WARNINGS"
285 The use of temporary variable is mandatory. A common
286 mistake is to attempt to use a buffer directly as follows:
290 \& unsigned char *buf;
292 \& len = i2d_X509(x, NULL);
294 \& buf = OPENSSL_malloc(len);
299 \& i2d_X509(x, &buf);
301 \& /* Other stuff ... */
303 \& OPENSSL_free(buf);
306 This code will result in \fBbuf\fR apparently containing garbage because
307 it was incremented after the call to point after the data just written.
308 Also \fBbuf\fR will no longer contain the pointer allocated by \fB\f(BIOPENSSL_malloc()\fB\fR
309 and the subsequent call to \fB\f(BIOPENSSL_free()\fB\fR may well crash.
311 The auto allocation feature (setting buf to \s-1NULL\s0) only works on OpenSSL
312 0.9.7 and later. Attempts to use it on earlier versions will typically
313 cause a segmentation violation.
315 Another trap to avoid is misuse of the \fBxp\fR argument to \fB\f(BId2i_X509()\fB\fR:
320 \& if (!d2i_X509(&x, &p, len))
324 This will probably crash somewhere in \fB\f(BId2i_X509()\fB\fR. The reason for this
325 is that the variable \fBx\fR is uninitialized and an attempt will be made to
326 interpret its (invalid) value as an \fBX509\fR structure, typically causing
327 a segmentation violation. If \fBx\fR is set to \s-1NULL\s0 first then this will not
331 In some versions of OpenSSL the \*(L"reuse\*(R" behaviour of \fId2i_X509()\fR when
332 \&\fB*px\fR is valid is broken and some parts of the reused structure may
333 persist if they are not present in the new one. As a result the use
334 of this \*(L"reuse\*(R" behaviour is strongly discouraged.
336 \&\fIi2d_X509()\fR will not return an error in many versions of OpenSSL,
337 if mandatory fields are not initialized due to a programming error
338 then the encoded structure may contain invalid data or omit the
339 fields entirely and will not be parsed by \fId2i_X509()\fR. This may be
340 fixed in future so code should not assume that \fIi2d_X509()\fR will
343 .IX Header "RETURN VALUES"
344 \&\fId2i_X509()\fR, \fId2i_X509_bio()\fR and \fId2i_X509_fp()\fR return a valid \fBX509\fR structure
345 or \fB\s-1NULL\s0\fR if an error occurs. The error code that can be obtained by
346 \&\fIERR_get_error\fR\|(3).
348 \&\fIi2d_X509()\fR returns the number of bytes successfully encoded or a negative
349 value if an error occurs. The error code can be obtained by
350 \&\fIERR_get_error\fR\|(3).
352 \&\fIi2d_X509_bio()\fR and \fIi2d_X509_fp()\fR return 1 for success and 0 if an error
353 occurs The error code can be obtained by \fIERR_get_error\fR\|(3).
355 .IX Header "SEE ALSO"
356 \&\fIERR_get_error\fR\|(3)
359 d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio and i2d_X509_fp
360 are available in all versions of SSLeay and OpenSSL.