Distinguished-Name validator in pure C

dn_validator.c

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

#define PARSER_KEY				0x001
#define PARSER_VALUE			0x002
#define PARSER_ESC				0x004
#define PARSER_SPACE			0x008

#define KEY_DC					((0x4443))
#define KEY_CN					((0x434e))
#define KEY_OU					((0x4f55))
#define KEY_O					((0x4f))
#define KEY_STREET				((0x535452454554))
#define KEY_ST					((0x5354))
#define KEY_L					((0x4c))
#define KEY_C					((0x43))
#define KEY_UID					((0x554944))

char	*dn_validator(char *str, const char **err);


int
main(int argc, char **argv)
{
	char *p, *dn;
	const char *err = NULL;
	if (argc != 2) {
		fprintf(stderr, "Usage: %s \"DistinguishedName\"\n", argv[0]);
		return -1;
	}

	if ((dn = strdup(argv[1])) == NULL) {
		return -1;
	}

	if ((p = dn_validator(argv[1], &err))) {
		fprintf(stderr, "%s: '%s'\n", err, p);
		return -1;
	}
	free(dn);
	return 0;
}

char *
dn_validator(char *str, const char **err)
{
    char *key = NULL, *value = NULL, *p;
    u_char parser = PARSER_KEY;
    u_int64_t key_magic = 0;

    p = str;
    while (1) {
		if (parser & PARSER_KEY) {
			if (!key) {
				key = p;
				value = NULL;
			}
			if (*p != '=')
				key_magic = (key_magic << 8 | toupper(*p));
		} else if ((parser & PARSER_VALUE) && !value) {
			if (*p == ' ' || *p == '#') {
				*err = "Invalid character";
				return p;
			}
			value = p;
		}

		if (parser & PARSER_ESC && *p == ',')
			goto escaped;

		switch(*p) {
		case 0x3d:	// equal sign
			if (!key || value || parser & PARSER_ESC) {
				*err = "Invalid character";
				return p;
			}
			*p = '\0';
			parser = PARSER_VALUE;
			break;
		case 0x00: // EOL
		case 0x2c: // separator comma
			if (!key || !value) {
				*err = (!key)? "Missing Key": "Missing Value";
				return p;
			}
			if (parser & (PARSER_ESC | PARSER_SPACE)) {
				*err = "Invalid character";
				return p;
			}
			switch (key_magic) {
			case KEY_DC:
			case KEY_CN:
			case KEY_OU:
			case KEY_O:
			case KEY_STREET:
			case KEY_ST:
			case KEY_L:
			case KEY_C:
			case KEY_UID:
				break;
			case 0x00:
				*err = "Missing Key";
				return p;
			default:
				*err = "Invalid key";
				return key;
			}

			parser = PARSER_KEY;
			key = value = NULL;
			key_magic = 0;
			if (*p == '\0')
				goto done;
			*p = '\0';
			break;
		case 0x5c: // backslash
			if (!(parser & PARSER_ESC)) {
				parser |= PARSER_ESC;
				break;
			}
		case 0x0a:	// CR
		case 0x0d:	// LF
		case 0x22:	// "
		case 0x27:	// '
		case 0x2b:	// +
		case 0x2f:	// slash
		case 0x3b:	// ;
		case 0x3c:	// <
		case 0x3e:	// >
			if (!(parser & PARSER_ESC)) {
				*err = "Invalid character";
				return p;
			}
		case 0x20 ... 0x21:
		case 0x23 ... 0x26:
		case 0x28 ... 0x2a:
		case 0x2d ... 0x2e:
		case 0x30 ... 0x3a:
		case 0x3f ... 0x5b:
		case 0x5d ... 0x7e:
			if (*p == ' ' && !(parser & PARSER_ESC))
				parser |= PARSER_SPACE;
			else
				parser &= ~PARSER_SPACE;
			if (*p == '\\' && !(parser & PARSER_ESC))
				parser = PARSER_ESC;
			else if (parser & PARSER_ESC)	/* ASCII escaped */
escaped:
				parser &= ~PARSER_ESC;
			break;
		default:
			*err = "Invalid character";
			return p;
		}
		p++;
    }
done:
    return NULL;
}