d2i_X509 man page on MirBSD

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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 functions

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 success-
     ful 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 success-
     ful *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.

MirOS BSD #10-current	   2005-02-05				1

D2I_X509(3)		     OpenSSL		      D2I_X509(3)

     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 opera-
     tion 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 structure:

      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;

MirOS BSD #10-current	   2005-02-05				2

D2I_X509(3)		     OpenSSL		      D2I_X509(3)

      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 follows:

      int len;
      unsigned char *buf;

      len = i2d_X509(x, NULL);

      buf = OPENSSL_malloc(len);

MirOS BSD #10-current	   2005-02-05				3

D2I_X509(3)		     OpenSSL		      D2I_X509(3)

      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 segmentation 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" behaviour 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 contain
     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).

MirOS BSD #10-current	   2005-02-05				4

D2I_X509(3)		     OpenSSL		      D2I_X509(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 versions of SSLeay and
     OpenSSL.

MirOS BSD #10-current	   2005-02-05				5

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