Creating a Network of Trust Using X.509 Certifi cates - Implementing SSL/TLS Using Cryptography and PKI - page 254

Listing 5-4: “asn1.h” constants
#define ASN1_CLASS_UNIVERSAL 0
#define ASN1_CLASS_APPLICATION 1
#define ASN1_CONTEXT_SPECIFIC 2
#define ASN1_PRIVATE 3
#define ASN1_BER 0
#define ASN1_BOOLEAN 1
#define ASN1_INTEGER 2
#define ASN1_BIT_STRING 3
#define ASN1_OCTET_STRING 4
#define ASN1_NULL 5
#define ASN1_OBJECT_IDENTIFIER 6
#define ASN1_OBJECT_DESCRIPTOR 7
#define ASN1_INSTANCE_OF_EXTERNAL 8
#define ASN1_REAL 9
#define ASN1_ENUMERATED 10
#define ASN1_EMBEDDED_PPV 11
#define ASN1_UTF8_STRING 12
#define ASN1_RELATIVE_OID 13
// 14 & 15 undefined
#define ASN1_SEQUENCE 16
#define ASN1_SET 17
#define ASN1_NUMERIC_STRING 18
#define ASN1_PRINTABLE_STRING 19
#define ASN1_TELETEX_STRING 20
#define ASN1_T61_STRING 20
#define ASN1_VIDEOTEX_STRING 21
#define ASN1_IA5_STRING 22
#define ASN1_UTC_TIME 23
#define ASN1_GENERALIZED_TIME 24
#define ASN1_GRAPHIC_STRING 25
#define ASN1_VISIBLE_STRING 26
#define ASN1_ISO64_STRING 26
#define ASN1_GENERAL_STRING 27
#define ASN1_UNIVERSAL_STRING 28
#define ASN1_CHARACTER_STRING 29
#define ASN1_BMP_STRING 30
The recursive ASN.1 parser routine itself is surprisingly simple (see Listing 5-5).
Listing 5-5: “asn1.c” asn1parse
int asn1parse( const unsigned char *buffer,
int length,
struct asn1struct *top_level_token )
{
unsigned int tag;
unsigned char tag_length_byte;
unsigned long tag_length;
const unsigned char *ptr;