src/lib-dns/dns-util.c

/* Copyright (c) 2010-2018 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "dns-util.h"

/**
  return first position from b->a of c or a if not found
 */
static inline
const char *strchr_ba(const char *a, const char *b, char c)
{
    for(;b>a && *b != c; b--);
    return b;
}

int dns_ncompare(const char *a, const char *b, size_t n)
{
    if (a == NULL && b == NULL) return 0;
    if (a == NULL && b != NULL) return 1;
    if (a != NULL && b == NULL) return -1;

    for(size_t i = 0; i < n &&
              *a != '\0' &&
              *b != '\0' &&
              dns_tolower(*a) == dns_tolower(*b);
        i++, a++, b++);

    return dns_tolower(*a) - dns_tolower(*b);
}

int dns_compare(const char *a, const char *b)
{
    return dns_ncompare(a, b, (size_t)-1);
}

int dns_compare_labels(const char *a, const char *b)
{
    if (a == NULL && b == NULL) return 0;
    if (a == NULL && b != NULL) return 1;
    if (a != NULL && b == NULL) return -1;

    const char *ptr_a = a + strlen(a);
    const char *ptr_b = b + strlen(b);
    const char *label_a = ptr_a, *label_b = ptr_b;
    int comp = 0;

    while(comp == 0 && ptr_a > a && ptr_b > b) {
        /* look for start of label, including dot */
        label_a = strchr_ba(a, ptr_a, '.');
        label_b = strchr_ba(b, ptr_b, '.');
        if (ptr_a - label_a != ptr_b - label_b)
            /* compare labels up to minimum length
               but include \0 to make sure that we
               don't consider alpha and alphabet
               equal */
            return dns_ncompare(label_a, label_b,
                       I_MIN(ptr_a - label_a,
                         ptr_b - label_b)+1);
        comp = dns_ncompare(label_a, label_b, ptr_a -label_a);
        ptr_a = label_a - 1;
        ptr_b = label_b - 1;
    }

    return dns_tolower(*label_a) - dns_tolower(*label_b);
}

int dns_match_wildcard(const char *name, const char *mask)
{
    i_assert(name != NULL && mask != NULL);

    for(;*name != '\0' && *mask != '\0'; name++, mask++) {
        switch(*mask) {
        case '*':
            name = strchr(name, '.');
            if (name == NULL || mask[1] != '.') return -1;
            mask++;
            break;
        case '?':
            break;
        default:
            if (dns_tolower(*name) != dns_tolower(*mask)) return -1;
        }
    }
    if (*mask == '*') mask++;
    return dns_tolower(*name) == dns_tolower(*mask) ? 0 : -1;
}