d2i_X509(3)                 OpenSSL                 d2i_X509(3)





NAME
       d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp,
       i2d_X509_bio, i2d_X509_fp - X509 encode and decode func-
       tions

SYNOPSIS
        #include <openssl/x509.h>

        X509 *d2i_X509(X509 **px, unsigned char **in, int len);
        int i2d_X509(X509 *x, unsigned char **out);

        X509 *d2i_X509_bio(BIO *bp, X509 **x);
        X509 *d2i_X509_fp(FILE *fp, X509 **x);

        int i2d_X509_bio(X509 *x, BIO *bp);
        int i2d_X509_fp(X509 *x, FILE *fp);

DESCRIPTION
       The X509 encode and decode routines encode and parse an
       X509 structure, which represents an X509 certificate.

       d2i_X509() attempts to decode len bytes at *out. If suc-
       cessful a pointer to the X509 structure is returned. If
       an error occurred then NULL is returned. If px is not
       NULL then the returned structure is written to *px. If
       *px is not NULL then it is assumed that *px contains a
       valid X509 structure and an attempt is made to reuse it.
       If the call is successful *out is incremented to the
       byte following the parsed data.

       i2d_X509() encodes the structure pointed to by x into
       DER format.  If out is not NULL is writes the DER
       encoded data to the buffer at *out, and increments it to
       point after the data just written.  If the return value
       is negative an error occurred, otherwise it returns the
       length of the encoded data.

       For OpenSSL 0.9.7 and later if *out is NULL memory will
       be allocated for a buffer and the encoded data written
       to it. In this case *out is not incremented and it
       points to the start of the data just written.

       d2i_X509_bio() is similar to d2i_X509() except it
       attempts to parse data from BIO bp.

       d2i_X509_fp() is similar to d2i_X509() except it
       attempts to parse data from FILE pointer fp.

       i2d_X509_bio() is similar to i2d_X509() except it writes
       the encoding of the structure x to BIO bp and it returns
       1 for success and 0 for failure.

       i2d_X509_fp() is similar to i2d_X509() except it writes
       the encoding of the structure x to BIO bp and it returns
       1 for success and 0 for failure.

NOTES
       The letters i and d in for example i2d_X509 stand for
       "internal" (that is an internal C structure) and "DER".
       So that i2d_X509 converts from internal to DER.

       The functions can also understand BER forms.

       The actual X509 structure passed to i2d_X509() must be a
       valid populated X509 structure it can not simply be fed
       with an empty structure such as that returned by
       X509_new().

       The encoded data is in binary form and may contain
       embedded zeroes.  Therefore any FILE pointers or BIOs
       should be opened in binary mode.  Functions such as
       strlen() will not return the correct length of the
       encoded structure.

       The ways that *in and *out are incremented after the
       operation can trap the unwary. See the WARNINGS section
       for some common errors.

       The reason for the auto increment behaviour is to
       reflect a typical usage of ASN1 functions: after one
       structure is encoded or decoded another will processed
       after it.

EXAMPLES
       Allocate and encode the DER encoding of an X509 struc-
       ture:

        int len;
        unsigned char *buf, *p;

        len = i2d_X509(x, NULL);

        buf = OPENSSL_malloc(len);

        if (buf == NULL)
               /* error */

        p = buf;

        i2d_X509(x, &p);

       If you are using OpenSSL 0.9.7 or later then this can be
       simplified to:

        int len;
        unsigned char *buf;

        buf = NULL;

        len = i2d_X509(x, &buf);

        if (len < 0)
               /* error */

       Attempt to decode a buffer:

        X509 *x;

        unsigned char *buf, *p;

        int len;

        /* Something to setup buf and len */

        p = buf;

        x = d2i_X509(NULL, &p, len);

        if (x == NULL)
           /* Some error */

       Alternative technique:

        X509 *x;

        unsigned char *buf, *p;

        int len;

        /* Something to setup buf and len */

        p = buf;

        x = NULL;

        if(!d2i_X509(&x, &p, len))
           /* Some error */

WARNINGS
       The use of temporary variable is mandatory. A common
       mistake is to attempt to use a buffer directly as fol-
       lows:

        int len;
        unsigned char *buf;

        len = i2d_X509(x, NULL);

        buf = OPENSSL_malloc(len);

        if (buf == NULL)
               /* error */

        i2d_X509(x, &buf);

        /* Other stuff ... */

        OPENSSL_free(buf);

       This code will result in buf apparently containing
       garbage because it was incremented after the call to
       point after the data just written.  Also buf will no
       longer contain the pointer allocated by OPENSSL_malloc()
       and the subsequent call to OPENSSL_free() may well
       crash.

       The auto allocation feature (setting buf to NULL) only
       works on OpenSSL 0.9.7 and later. Attempts to use it on
       earlier versions will typically cause a segmentation
       violation.

       Another trap to avoid is misuse of the xp argument to
       d2i_X509():

        X509 *x;

        if (!d2i_X509(&x, &p, len))
               /* Some error */

       This will probably crash somewhere in d2i_X509(). The
       reason for this is that the variable x is uninitialized
       and an attempt will be made to interpret its (invalid)
       value as an X509 structure, typically causing a segmen-
       tation violation. If x is set to NULL first then this
       will not happen.

BUGS
       In some versions of OpenSSL the "reuse" behaviour of
       d2i_X509() when *px is valid is broken and some parts of
       the reused structure may persist if they are not present
       in the new one. As a result the use of this "reuse" be-
       haviour is strongly discouraged.

       i2d_X509() will not return an error in many versions of
       OpenSSL, if mandatory fields are not initialized due to
       a programming error then the encoded structure may con-
       tain invalid data or omit the fields entirely and will
       not be parsed by d2i_X509(). This may be fixed in future
       so code should not assume that i2d_X509() will always
       succeed.

RETURN VALUES
       d2i_X509(), d2i_X509_bio() and d2i_X509_fp() return a
       valid X509 structure or NULL if an error occurs. The
       error code that can be obtained by ERR_get_error(3).

       i2d_X509(), i2d_X509_bio() and i2d_X509_fp() return a
       the number of bytes successfully encoded or a negative
       value if an error occurs. The error code can be obtained
       by ERR_get_error(3).

       i2d_X509_bio() and i2d_X509_fp() returns 1 for success
       and 0 if an error occurs The error code can be obtained
       by ERR_get_error(3).

SEE ALSO
       ERR_get_error(3)

HISTORY
       d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp,
       i2d_X509_bio and i2d_X509_fp are available in all ver-
       sions of SSLeay and OpenSSL.



0.9.7c                     2002-11-14               d2i_X509(3)
