i2d_X509(3ssl)

1d2i_X509(3)                         OpenSSL                        d2i_X509(3)
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NAME

6       d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio,
7       i2d_X509_fp - X509 encode and decode functions
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SYNOPSIS

10        #include <openssl/x509.h>
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12        X509 *d2i_X509(X509 **px, const unsigned char **in, int len);
13        int i2d_X509(X509 *x, unsigned char **out);
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15        X509 *d2i_X509_bio(BIO *bp, X509 **x);
16        X509 *d2i_X509_fp(FILE *fp, X509 **x);
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18        int i2d_X509_bio(X509 *x, BIO *bp);
19        int i2d_X509_fp(X509 *x, FILE *fp);
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DESCRIPTION

22       The X509 encode and decode routines encode and parse an X509 structure,
23       which represents an X509 certificate.
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25       d2i_X509() attempts to decode len bytes at *in. If successful a pointer
26       to the X509 structure is returned. If an error occurred then NULL is
27       returned. If px is not NULL then the returned structure is written to
28       *px. If *px is not NULL then it is assumed that *px contains a valid
29       X509 structure and an attempt is made to reuse it. If the call is suc‐
30       cessful *in is incremented to the byte following the parsed data.
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32       i2d_X509() encodes the structure pointed to by x into DER format.  If
33       out is not NULL is writes the DER encoded data to the buffer at *out,
34       and increments it to point after the data just written.  If the return
35       value is negative an error occurred, otherwise it returns the length of
36       the encoded data.
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38       For OpenSSL 0.9.7 and later if *out is NULL memory will be allocated
39       for a buffer and the encoded data written to it. In this case *out is
40       not incremented and it points to the start of the data just written.
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42       d2i_X509_bio() is similar to d2i_X509() except it attempts to parse
43       data from BIO bp.
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45       d2i_X509_fp() is similar to d2i_X509() except it attempts to parse data
46       from FILE pointer fp.
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48       i2d_X509_bio() is similar to i2d_X509() except it writes the encoding
49       of the structure x to BIO bp and it returns 1 for success and 0 for
50       failure.
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52       i2d_X509_fp() is similar to i2d_X509() except it writes the encoding of
53       the structure x to BIO bp and it returns 1 for success and 0 for fail‐
54       ure.
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NOTES

57       The letters i and d in for example i2d_X509 stand for "internal" (that
58       is an internal C structure) and "DER". So that i2d_X509 converts from
59       internal to DER.
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61       The functions can also understand BER forms.
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63       The actual X509 structure passed to i2d_X509() must be a valid popu‐
64       lated X509 structure it can not simply be fed with an empty structure
65       such as that returned by X509_new().
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67       The encoded data is in binary form and may contain embedded zeroes.
68       Therefore any FILE pointers or BIOs should be opened in binary mode.
69       Functions such as strlen() will not return the correct length of the
70       encoded structure.
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72       The ways that *in and *out are incremented after the operation can trap
73       the unwary. See the WARNINGS section for some common errors.
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75       The reason for the auto increment behaviour is to reflect a typical
76       usage of ASN1 functions: after one structure is encoded or decoded
77       another will processed after it.
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EXAMPLES

80       Allocate and encode the DER encoding of an X509 structure:
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82        int len;
83        unsigned char *buf, *p;
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85        len = i2d_X509(x, NULL);
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87        buf = OPENSSL_malloc(len);
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89        if (buf == NULL)
90               /* error */
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92        p = buf;
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94        i2d_X509(x, &p);
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96       If you are using OpenSSL 0.9.7 or later then this can be simplified to:
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98        int len;
99        unsigned char *buf;
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101        buf = NULL;
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103        len = i2d_X509(x, &buf);
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105        if (len < 0)
106               /* error */
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108       Attempt to decode a buffer:
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110        X509 *x;
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112        unsigned char *buf, *p;
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114        int len;
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116        /* Something to setup buf and len */
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118        p = buf;
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120        x = d2i_X509(NULL, &p, len);
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122        if (x == NULL)
123           /* Some error */
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125       Alternative technique:
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127        X509 *x;
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129        unsigned char *buf, *p;
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131        int len;
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133        /* Something to setup buf and len */
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135        p = buf;
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137        x = NULL;
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139        if(!d2i_X509(&x, &p, len))
140           /* Some error */
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WARNINGS

143       The use of temporary variable is mandatory. A common mistake is to
144       attempt to use a buffer directly as follows:
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146        int len;
147        unsigned char *buf;
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149        len = i2d_X509(x, NULL);
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151        buf = OPENSSL_malloc(len);
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153        if (buf == NULL)
154               /* error */
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156        i2d_X509(x, &buf);
157
158        /* Other stuff ... */
159
160        OPENSSL_free(buf);
161
162       This code will result in buf apparently containing garbage because it
163       was incremented after the call to point after the data just written.
164       Also buf will no longer contain the pointer allocated by OPENSSL_mal‐
165       loc() and the subsequent call to OPENSSL_free() may well crash.
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167       The auto allocation feature (setting buf to NULL) only works on OpenSSL
168       0.9.7 and later. Attempts to use it on earlier versions will typically
169       cause a segmentation violation.
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171       Another trap to avoid is misuse of the xp argument to d2i_X509():
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173        X509 *x;
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175        if (!d2i_X509(&x, &p, len))
176               /* Some error */
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178       This will probably crash somewhere in d2i_X509(). The reason for this
179       is that the variable x is uninitialized and an attempt will be made to
180       interpret its (invalid) value as an X509 structure, typically causing a
181       segmentation violation. If x is set to NULL first then this will not
182       happen.
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BUGS

185       In some versions of OpenSSL the "reuse" behaviour of d2i_X509() when
186       *px is valid is broken and some parts of the reused structure may per‐
187       sist if they are not present in the new one. As a result the use of
188       this "reuse" behaviour is strongly discouraged.
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190       i2d_X509() will not return an error in many versions of OpenSSL, if
191       mandatory fields are not initialized due to a programming error then
192       the encoded structure may contain invalid data or omit the fields
193       entirely and will not be parsed by d2i_X509(). This may be fixed in
194       future so code should not assume that i2d_X509() will always succeed.
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RETURN VALUES

197       d2i_X509(), d2i_X509_bio() and d2i_X509_fp() return a valid X509 struc‐
198       ture or NULL if an error occurs. The error code that can be obtained by
199       ERR_get_error(3).
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201       i2d_X509(), i2d_X509_bio() and i2d_X509_fp() return a the number of
202       bytes successfully encoded or a negative value if an error occurs. The
203       error code can be obtained by ERR_get_error(3).
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205       i2d_X509_bio() and i2d_X509_fp() returns 1 for success and 0 if an
206       error occurs The error code can be obtained by ERR_get_error(3).
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HISTORY

212       d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio and
213       i2d_X509_fp are available in all versions of SSLeay and OpenSSL.
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2170.9.8b                            2005-07-13                       d2i_X509(3)