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135 .IX Title "d2i_X509 3"
136 .TH d2i_X509 3 "2016-09-22" "1.0.2i" "OpenSSL"
137 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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142 d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio,
143 i2d_X509_fp \- X509 encode and decode functions
145 .IX Header "SYNOPSIS"
147 \& #include <openssl/x509.h>
149 \& X509 *d2i_X509(X509 **px, const unsigned char **in, long len);
150 \& X509 *d2i_X509_AUX(X509 **px, const unsigned char **in, long len);
151 \& int i2d_X509(X509 *x, unsigned char **out);
152 \& int i2d_X509_AUX(X509 *x, unsigned char **out);
154 \& X509 *d2i_X509_bio(BIO *bp, X509 **x);
155 \& X509 *d2i_X509_fp(FILE *fp, X509 **x);
157 \& int i2d_X509_bio(BIO *bp, X509 *x);
158 \& int i2d_X509_fp(FILE *fp, X509 *x);
160 \& int i2d_re_X509_tbs(X509 *x, unsigned char **out);
163 .IX Header "DESCRIPTION"
164 The X509 encode and decode routines encode and parse an
165 \&\fBX509\fR structure, which represents an X509 certificate.
167 \&\fId2i_X509()\fR attempts to decode \fBlen\fR bytes at \fB*in\fR. If
168 successful a pointer to the \fBX509\fR structure is returned. If an error
169 occurred then \fB\s-1NULL\s0\fR is returned. If \fBpx\fR is not \fB\s-1NULL\s0\fR then the
170 returned structure is written to \fB*px\fR. If \fB*px\fR is not \fB\s-1NULL\s0\fR
171 then it is assumed that \fB*px\fR contains a valid \fBX509\fR
172 structure and an attempt is made to reuse it. This \*(L"reuse\*(R" capability is present
173 for historical compatibility but its use is \fBstrongly discouraged\fR (see \s-1BUGS\s0
174 below, and the discussion in the \s-1RETURN VALUES\s0 section).
176 If the call is successful \fB*in\fR is incremented to the byte following the
179 \&\fId2i_X509_AUX()\fR is similar to \fId2i_X509()\fR but the input is expected to consist of
180 an X509 certificate followed by auxiliary trust information.
181 This is used by the \s-1PEM\s0 routines to read \*(L"\s-1TRUSTED CERTIFICATE\*(R"\s0 objects.
182 This function should not be called on untrusted input.
184 \&\fIi2d_X509()\fR encodes the structure pointed to by \fBx\fR into \s-1DER\s0 format.
185 If \fBout\fR is not \fB\s-1NULL\s0\fR is writes the \s-1DER\s0 encoded data to the buffer
186 at \fB*out\fR, and increments it to point after the data just written.
187 If the return value is negative an error occurred, otherwise it
188 returns the length of the encoded data.
190 For OpenSSL 0.9.7 and later if \fB*out\fR is \fB\s-1NULL\s0\fR memory will be
191 allocated for a buffer and the encoded data written to it. In this
192 case \fB*out\fR is not incremented and it points to the start of the
195 \&\fIi2d_X509_AUX()\fR is similar to \fIi2d_X509()\fR, but the encoded output contains both
196 the certificate and any auxiliary trust information.
197 This is used by the \s-1PEM\s0 routines to write \*(L"\s-1TRUSTED CERTIFICATE\*(R"\s0 objects.
198 Note, this is a non-standard OpenSSL-specific data format.
200 \&\fId2i_X509_bio()\fR is similar to \fId2i_X509()\fR except it attempts
201 to parse data from \s-1BIO \s0\fBbp\fR.
203 \&\fId2i_X509_fp()\fR is similar to \fId2i_X509()\fR except it attempts
204 to parse data from \s-1FILE\s0 pointer \fBfp\fR.
206 \&\fIi2d_X509_bio()\fR is similar to \fIi2d_X509()\fR except it writes
207 the encoding of the structure \fBx\fR to \s-1BIO \s0\fBbp\fR and it
208 returns 1 for success and 0 for failure.
210 \&\fIi2d_X509_fp()\fR is similar to \fIi2d_X509()\fR except it writes
211 the encoding of the structure \fBx\fR to \s-1BIO \s0\fBbp\fR and it
212 returns 1 for success and 0 for failure.
214 \&\fIi2d_re_X509_tbs()\fR is similar to \fIi2d_X509()\fR except it encodes
215 only the TBSCertificate portion of the certificate.
218 The letters \fBi\fR and \fBd\fR in for example \fBi2d_X509\fR stand for
219 \&\*(L"internal\*(R" (that is an internal C structure) and \*(L"\s-1DER\*(R".\s0 So
220 \&\fBi2d_X509\fR converts from internal to \s-1DER.\s0 The \*(L"re\*(R" in
221 \&\fBi2d_re_X509_tbs\fR stands for \*(L"re-encode\*(R", and ensures that a fresh
222 encoding is generated in case the object has been modified after
223 creation (see the \s-1BUGS\s0 section).
225 The functions can also understand \fB\s-1BER\s0\fR forms.
227 The actual X509 structure passed to \fIi2d_X509()\fR must be a valid
228 populated \fBX509\fR structure it can \fBnot\fR simply be fed with an
229 empty structure such as that returned by \fIX509_new()\fR.
231 The encoded data is in binary form and may contain embedded zeroes.
232 Therefore any \s-1FILE\s0 pointers or BIOs should be opened in binary mode.
233 Functions such as \fB\f(BIstrlen()\fB\fR will \fBnot\fR return the correct length
234 of the encoded structure.
236 The ways that \fB*in\fR and \fB*out\fR are incremented after the operation
237 can trap the unwary. See the \fB\s-1WARNINGS\s0\fR section for some common
240 The reason for the auto increment behaviour is to reflect a typical
241 usage of \s-1ASN1\s0 functions: after one structure is encoded or decoded
242 another will processed after it.
244 .IX Header "EXAMPLES"
245 Allocate and encode the \s-1DER\s0 encoding of an X509 structure:
249 \& unsigned char *buf, *p;
251 \& len = i2d_X509(x, NULL);
253 \& buf = OPENSSL_malloc(len);
263 If you are using OpenSSL 0.9.7 or later then this can be
268 \& unsigned char *buf;
272 \& len = i2d_X509(x, &buf);
278 Attempt to decode a buffer:
283 \& unsigned char *buf, *p;
287 \& /* Something to setup buf and len */
291 \& x = d2i_X509(NULL, &p, len);
297 Alternative technique:
302 \& unsigned char *buf, *p;
306 \& /* Something to setup buf and len */
312 \& if(!d2i_X509(&x, &p, len))
316 .IX Header "WARNINGS"
317 The use of temporary variable is mandatory. A common
318 mistake is to attempt to use a buffer directly as follows:
322 \& unsigned char *buf;
324 \& len = i2d_X509(x, NULL);
326 \& buf = OPENSSL_malloc(len);
331 \& i2d_X509(x, &buf);
333 \& /* Other stuff ... */
335 \& OPENSSL_free(buf);
338 This code will result in \fBbuf\fR apparently containing garbage because
339 it was incremented after the call to point after the data just written.
340 Also \fBbuf\fR will no longer contain the pointer allocated by \fB\f(BIOPENSSL_malloc()\fB\fR
341 and the subsequent call to \fB\f(BIOPENSSL_free()\fB\fR may well crash.
343 The auto allocation feature (setting buf to \s-1NULL\s0) only works on OpenSSL
344 0.9.7 and later. Attempts to use it on earlier versions will typically
345 cause a segmentation violation.
347 Another trap to avoid is misuse of the \fBxp\fR argument to \fB\f(BId2i_X509()\fB\fR:
352 \& if (!d2i_X509(&x, &p, len))
356 This will probably crash somewhere in \fB\f(BId2i_X509()\fB\fR. The reason for this
357 is that the variable \fBx\fR is uninitialized and an attempt will be made to
358 interpret its (invalid) value as an \fBX509\fR structure, typically causing
359 a segmentation violation. If \fBx\fR is set to \s-1NULL\s0 first then this will not
363 In some versions of OpenSSL the \*(L"reuse\*(R" behaviour of \fId2i_X509()\fR when
364 \&\fB*px\fR is valid is broken and some parts of the reused structure may
365 persist if they are not present in the new one. As a result the use
366 of this \*(L"reuse\*(R" behaviour is strongly discouraged.
368 \&\fIi2d_X509()\fR will not return an error in many versions of OpenSSL,
369 if mandatory fields are not initialized due to a programming error
370 then the encoded structure may contain invalid data or omit the
371 fields entirely and will not be parsed by \fId2i_X509()\fR. This may be
372 fixed in future so code should not assume that \fIi2d_X509()\fR will
375 The encoding of the TBSCertificate portion of a certificate is cached
376 in the \fBX509\fR structure internally to improve encoding performance
377 and to ensure certificate signatures are verified correctly in some
378 certificates with broken (non-DER) encodings.
380 Any function which encodes an X509 structure such as \fIi2d_X509()\fR,
381 \&\fIi2d_X509_fp()\fR or \fIi2d_X509_bio()\fR may return a stale encoding if the
382 \&\fBX509\fR structure has been modified after deserialization or previous
385 If, after modification, the \fBX509\fR object is re-signed with \fIX509_sign()\fR,
386 the encoding is automatically renewed. Otherwise, the encoding of the
387 TBSCertificate portion of the \fBX509\fR can be manually renewed by calling
388 \&\fIi2d_re_X509_tbs()\fR.
390 .IX Header "RETURN VALUES"
391 \&\fId2i_X509()\fR, \fId2i_X509_bio()\fR and \fId2i_X509_fp()\fR return a valid \fBX509\fR structure
392 or \fB\s-1NULL\s0\fR if an error occurs. The error code that can be obtained by
393 \&\fIERR_get_error\fR\|(3). If the \*(L"reuse\*(R" capability has been used
394 with a valid X509 structure being passed in via \fBpx\fR then the object is not
395 freed in the event of error but may be in a potentially invalid or inconsistent
398 \&\fIi2d_X509()\fR returns the number of bytes successfully encoded or a negative
399 value if an error occurs. The error code can be obtained by
400 \&\fIERR_get_error\fR\|(3).
402 \&\fIi2d_X509_bio()\fR and \fIi2d_X509_fp()\fR return 1 for success and 0 if an error
403 occurs The error code can be obtained by \fIERR_get_error\fR\|(3).
405 .IX Header "SEE ALSO"
406 \&\fIERR_get_error\fR\|(3)
409 d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio and i2d_X509_fp
410 are available in all versions of SSLeay and OpenSSL.