5 d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio,
6 i2d_X509_fp - X509 encode and decode functions
10 #include <openssl/x509.h>
12 X509 *d2i_X509(X509 **px, const unsigned char **in, long len);
13 X509 *d2i_X509_AUX(X509 **px, const unsigned char **in, long len);
14 int i2d_X509(X509 *x, unsigned char **out);
15 int i2d_X509_AUX(X509 *x, unsigned char **out);
17 X509 *d2i_X509_bio(BIO *bp, X509 **x);
18 X509 *d2i_X509_fp(FILE *fp, X509 **x);
20 int i2d_X509_bio(BIO *bp, X509 *x);
21 int i2d_X509_fp(FILE *fp, X509 *x);
23 int i2d_re_X509_tbs(X509 *x, unsigned char **out);
27 The X509 encode and decode routines encode and parse an
28 B<X509> structure, which represents an X509 certificate.
30 d2i_X509() attempts to decode B<len> bytes at B<*in>. If
31 successful a pointer to the B<X509> structure is returned. If an error
32 occurred then B<NULL> is returned. If B<px> is not B<NULL> then the
33 returned structure is written to B<*px>. If B<*px> is not B<NULL>
34 then it is assumed that B<*px> contains a valid B<X509>
35 structure and an attempt is made to reuse it. This "reuse" capability is present
36 for historical compatibility but its use is B<strongly discouraged> (see BUGS
37 below, and the discussion in the RETURN VALUES section).
39 If the call is successful B<*in> is incremented to the byte following the
42 d2i_X509_AUX() is similar to d2i_X509() but the input is expected to consist of
43 an X509 certificate followed by auxiliary trust information.
44 This is used by the PEM routines to read "TRUSTED CERTIFICATE" objects.
45 This function should not be called on untrusted input.
47 i2d_X509() encodes the structure pointed to by B<x> into DER format.
48 If B<out> is not B<NULL> is writes the DER encoded data to the buffer
49 at B<*out>, and increments it to point after the data just written.
50 If the return value is negative an error occurred, otherwise it
51 returns the length of the encoded data.
53 For OpenSSL 0.9.7 and later if B<*out> is B<NULL> memory will be
54 allocated for a buffer and the encoded data written to it. In this
55 case B<*out> is not incremented and it points to the start of the
58 i2d_X509_AUX() is similar to i2d_X509(), but the encoded output contains both
59 the certificate and any auxiliary trust information.
60 This is used by the PEM routines to write "TRUSTED CERTIFICATE" objects.
61 Note, this is a non-standard OpenSSL-specific data format.
63 d2i_X509_bio() is similar to d2i_X509() except it attempts
64 to parse data from BIO B<bp>.
66 d2i_X509_fp() is similar to d2i_X509() except it attempts
67 to parse data from FILE pointer B<fp>.
69 i2d_X509_bio() is similar to i2d_X509() except it writes
70 the encoding of the structure B<x> to BIO B<bp> and it
71 returns 1 for success and 0 for failure.
73 i2d_X509_fp() is similar to i2d_X509() except it writes
74 the encoding of the structure B<x> to BIO B<bp> and it
75 returns 1 for success and 0 for failure.
77 i2d_re_X509_tbs() is similar to i2d_X509() except it encodes
78 only the TBSCertificate portion of the certificate.
82 The letters B<i> and B<d> in for example B<i2d_X509> stand for
83 "internal" (that is an internal C structure) and "DER". So
84 B<i2d_X509> converts from internal to DER. The "re" in
85 B<i2d_re_X509_tbs> stands for "re-encode", and ensures that a fresh
86 encoding is generated in case the object has been modified after
87 creation (see the BUGS section).
89 The functions can also understand B<BER> forms.
91 The actual X509 structure passed to i2d_X509() must be a valid
92 populated B<X509> structure it can B<not> simply be fed with an
93 empty structure such as that returned by X509_new().
95 The encoded data is in binary form and may contain embedded zeroes.
96 Therefore any FILE pointers or BIOs should be opened in binary mode.
97 Functions such as B<strlen()> will B<not> return the correct length
98 of the encoded structure.
100 The ways that B<*in> and B<*out> are incremented after the operation
101 can trap the unwary. See the B<WARNINGS> section for some common
104 The reason for the auto increment behaviour is to reflect a typical
105 usage of ASN1 functions: after one structure is encoded or decoded
106 another will processed after it.
110 Allocate and encode the DER encoding of an X509 structure:
113 unsigned char *buf, *p;
115 len = i2d_X509(x, NULL);
117 buf = OPENSSL_malloc(len);
126 If you are using OpenSSL 0.9.7 or later then this can be
135 len = i2d_X509(x, &buf);
140 Attempt to decode a buffer:
144 unsigned char *buf, *p;
148 /* Something to setup buf and len */
152 x = d2i_X509(NULL, &p, len);
157 Alternative technique:
161 unsigned char *buf, *p;
165 /* Something to setup buf and len */
171 if(!d2i_X509(&x, &p, len))
177 The use of temporary variable is mandatory. A common
178 mistake is to attempt to use a buffer directly as follows:
183 len = i2d_X509(x, NULL);
185 buf = OPENSSL_malloc(len);
192 /* Other stuff ... */
196 This code will result in B<buf> apparently containing garbage because
197 it was incremented after the call to point after the data just written.
198 Also B<buf> will no longer contain the pointer allocated by B<OPENSSL_malloc()>
199 and the subsequent call to B<OPENSSL_free()> may well crash.
201 The auto allocation feature (setting buf to NULL) only works on OpenSSL
202 0.9.7 and later. Attempts to use it on earlier versions will typically
203 cause a segmentation violation.
205 Another trap to avoid is misuse of the B<xp> argument to B<d2i_X509()>:
209 if (!d2i_X509(&x, &p, len))
212 This will probably crash somewhere in B<d2i_X509()>. The reason for this
213 is that the variable B<x> is uninitialized and an attempt will be made to
214 interpret its (invalid) value as an B<X509> structure, typically causing
215 a segmentation violation. If B<x> is set to NULL first then this will not
220 In some versions of OpenSSL the "reuse" behaviour of d2i_X509() when
221 B<*px> is valid is broken and some parts of the reused structure may
222 persist if they are not present in the new one. As a result the use
223 of this "reuse" behaviour is strongly discouraged.
225 i2d_X509() will not return an error in many versions of OpenSSL,
226 if mandatory fields are not initialized due to a programming error
227 then the encoded structure may contain invalid data or omit the
228 fields entirely and will not be parsed by d2i_X509(). This may be
229 fixed in future so code should not assume that i2d_X509() will
232 The encoding of the TBSCertificate portion of a certificate is cached
233 in the B<X509> structure internally to improve encoding performance
234 and to ensure certificate signatures are verified correctly in some
235 certificates with broken (non-DER) encodings.
237 Any function which encodes an X509 structure such as i2d_X509(),
238 i2d_X509_fp() or i2d_X509_bio() may return a stale encoding if the
239 B<X509> structure has been modified after deserialization or previous
242 If, after modification, the B<X509> object is re-signed with X509_sign(),
243 the encoding is automatically renewed. Otherwise, the encoding of the
244 TBSCertificate portion of the B<X509> can be manually renewed by calling
249 d2i_X509(), d2i_X509_bio() and d2i_X509_fp() return a valid B<X509> structure
250 or B<NULL> if an error occurs. The error code that can be obtained by
251 L<ERR_get_error(3)|ERR_get_error(3)>. If the "reuse" capability has been used
252 with a valid X509 structure being passed in via B<px> then the object is not
253 freed in the event of error but may be in a potentially invalid or inconsistent
256 i2d_X509() returns the number of bytes successfully encoded or a negative
257 value if an error occurs. The error code can be obtained by
258 L<ERR_get_error(3)|ERR_get_error(3)>.
260 i2d_X509_bio() and i2d_X509_fp() return 1 for success and 0 if an error
261 occurs The error code can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
265 L<ERR_get_error(3)|ERR_get_error(3)>
269 d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio and i2d_X509_fp
270 are available in all versions of SSLeay and OpenSSL.