1=pod 2 3=head1 NAME 4 5d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio, 6i2d_X509_fp - X509 encode and decode functions 7 8=head1 SYNOPSIS 9 10 #include <openssl/x509.h> 11 12 X509 *d2i_X509(X509 **px, const unsigned char **in, int len); 13 int i2d_X509(X509 *x, unsigned char **out); 14 15 X509 *d2i_X509_bio(BIO *bp, X509 **x); 16 X509 *d2i_X509_fp(FILE *fp, X509 **x); 17 18 int i2d_X509_bio(BIO *bp, X509 *x); 19 int i2d_X509_fp(FILE *fp, X509 *x); 20 21=head1 DESCRIPTION 22 23The X509 encode and decode routines encode and parse an 24B<X509> structure, which represents an X509 certificate. 25 26d2i_X509() attempts to decode B<len> bytes at B<*in>. If 27successful a pointer to the B<X509> structure is returned. If an error 28occurred then B<NULL> is returned. If B<px> is not B<NULL> then the 29returned structure is written to B<*px>. If B<*px> is not B<NULL> 30then it is assumed that B<*px> contains a valid B<X509> 31structure and an attempt is made to reuse it. If the call is 32successful B<*in> is incremented to the byte following the 33parsed data. 34 35i2d_X509() encodes the structure pointed to by B<x> into DER format. 36If B<out> is not B<NULL> is writes the DER encoded data to the buffer 37at B<*out>, and increments it to point after the data just written. 38If the return value is negative an error occurred, otherwise it 39returns the length of the encoded data. 40 41For OpenSSL 0.9.7 and later if B<*out> is B<NULL> memory will be 42allocated for a buffer and the encoded data written to it. In this 43case B<*out> is not incremented and it points to the start of the 44data just written. 45 46d2i_X509_bio() is similar to d2i_X509() except it attempts 47to parse data from BIO B<bp>. 48 49d2i_X509_fp() is similar to d2i_X509() except it attempts 50to parse data from FILE pointer B<fp>. 51 52i2d_X509_bio() is similar to i2d_X509() except it writes 53the encoding of the structure B<x> to BIO B<bp> and it 54returns 1 for success and 0 for failure. 55 56i2d_X509_fp() is similar to i2d_X509() except it writes 57the encoding of the structure B<x> to BIO B<bp> and it 58returns 1 for success and 0 for failure. 59 60=head1 NOTES 61 62The letters B<i> and B<d> in for example B<i2d_X509> stand for 63"internal" (that is an internal C structure) and "DER". So that 64B<i2d_X509> converts from internal to DER. 65 66The functions can also understand B<BER> forms. 67 68The actual X509 structure passed to i2d_X509() must be a valid 69populated B<X509> structure it can B<not> simply be fed with an 70empty structure such as that returned by X509_new(). 71 72The encoded data is in binary form and may contain embedded zeroes. 73Therefore any FILE pointers or BIOs should be opened in binary mode. 74Functions such as B<strlen()> will B<not> return the correct length 75of the encoded structure. 76 77The ways that B<*in> and B<*out> are incremented after the operation 78can trap the unwary. See the B<WARNINGS> section for some common 79errors. 80 81The reason for the auto increment behaviour is to reflect a typical 82usage of ASN1 functions: after one structure is encoded or decoded 83another will processed after it. 84 85=head1 EXAMPLES 86 87Allocate and encode the DER encoding of an X509 structure: 88 89 int len; 90 unsigned char *buf, *p; 91 92 len = i2d_X509(x, NULL); 93 94 buf = OPENSSL_malloc(len); 95 96 if (buf == NULL) 97 /* error */ 98 99 p = buf; 100 101 i2d_X509(x, &p); 102 103If you are using OpenSSL 0.9.7 or later then this can be 104simplified to: 105 106 107 int len; 108 unsigned char *buf; 109 110 buf = NULL; 111 112 len = i2d_X509(x, &buf); 113 114 if (len < 0) 115 /* error */ 116 117Attempt to decode a buffer: 118 119 X509 *x; 120 121 unsigned char *buf, *p; 122 123 int len; 124 125 /* Something to setup buf and len */ 126 127 p = buf; 128 129 x = d2i_X509(NULL, &p, len); 130 131 if (x == NULL) 132 /* Some error */ 133 134Alternative technique: 135 136 X509 *x; 137 138 unsigned char *buf, *p; 139 140 int len; 141 142 /* Something to setup buf and len */ 143 144 p = buf; 145 146 x = NULL; 147 148 if(!d2i_X509(&x, &p, len)) 149 /* Some error */ 150 151 152=head1 WARNINGS 153 154The use of temporary variable is mandatory. A common 155mistake is to attempt to use a buffer directly as follows: 156 157 int len; 158 unsigned char *buf; 159 160 len = i2d_X509(x, NULL); 161 162 buf = OPENSSL_malloc(len); 163 164 if (buf == NULL) 165 /* error */ 166 167 i2d_X509(x, &buf); 168 169 /* Other stuff ... */ 170 171 OPENSSL_free(buf); 172 173This code will result in B<buf> apparently containing garbage because 174it was incremented after the call to point after the data just written. 175Also B<buf> will no longer contain the pointer allocated by B<OPENSSL_malloc()> 176and the subsequent call to B<OPENSSL_free()> may well crash. 177 178The auto allocation feature (setting buf to NULL) only works on OpenSSL 1790.9.7 and later. Attempts to use it on earlier versions will typically 180cause a segmentation violation. 181 182Another trap to avoid is misuse of the B<xp> argument to B<d2i_X509()>: 183 184 X509 *x; 185 186 if (!d2i_X509(&x, &p, len)) 187 /* Some error */ 188 189This will probably crash somewhere in B<d2i_X509()>. The reason for this 190is that the variable B<x> is uninitialized and an attempt will be made to 191interpret its (invalid) value as an B<X509> structure, typically causing 192a segmentation violation. If B<x> is set to NULL first then this will not 193happen. 194 195=head1 BUGS 196 197In some versions of OpenSSL the "reuse" behaviour of d2i_X509() when 198B<*px> is valid is broken and some parts of the reused structure may 199persist if they are not present in the new one. As a result the use 200of this "reuse" behaviour is strongly discouraged. 201 202i2d_X509() will not return an error in many versions of OpenSSL, 203if mandatory fields are not initialized due to a programming error 204then the encoded structure may contain invalid data or omit the 205fields entirely and will not be parsed by d2i_X509(). This may be 206fixed in future so code should not assume that i2d_X509() will 207always succeed. 208 209=head1 RETURN VALUES 210 211d2i_X509(), d2i_X509_bio() and d2i_X509_fp() return a valid B<X509> structure 212or B<NULL> if an error occurs. The error code that can be obtained by 213L<ERR_get_error(3)|ERR_get_error(3)>. 214 215i2d_X509() returns the number of bytes successfully encoded or a negative 216value if an error occurs. The error code can be obtained by 217L<ERR_get_error(3)|ERR_get_error(3)>. 218 219i2d_X509_bio() and i2d_X509_fp() return 1 for success and 0 if an error 220occurs The error code can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 221 222=head1 SEE ALSO 223 224L<ERR_get_error(3)|ERR_get_error(3)> 225 226=head1 HISTORY 227 228d2i_X509, i2d_X509, d2i_X509_bio, d2i_X509_fp, i2d_X509_bio and i2d_X509_fp 229are available in all versions of SSLeay and OpenSSL. 230 231=cut 232