lib-dns: Add DNS specific matching algorithms

RFC4343 and RFCRFC4592 compare and match algorithms

diff --git a/src/lib-dns/Makefile.am b/src/lib-dns/Makefile.am
index 751860a7c045c81ec6315f34ff026b5b5bae2177..4a0e8bc46f5fd99f3bafbc464b6f8e31c8a9447e 100644 (file)
--- a/src/lib-dns/Makefile.am
+++ b/src/lib-dns/Makefile.am
@@ -4,10 +4,12 @@ AM_CPPFLAGS = \
        -I$(top_srcdir)/src/lib
 
 libdns_la_SOURCES = \
-       dns-lookup.c
+       dns-lookup.c \
+       dns-util.c
 
 headers = \
-       dns-lookup.h
+       dns-lookup.h \
+       dns-util.h
 
 pkginc_libdir=$(pkgincludedir)
 pkginc_lib_HEADERS = $(headers)

diff --git a/src/lib-dns/dns-util.c b/src/lib-dns/dns-util.c
new file mode 100644 (file)
index 0000000..e88008f
--- /dev/null
+++ b/src/lib-dns/dns-util.c
@@ -0,0 +1,85 @@
+/* Copyright (c) 2010-2016 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;
+}

diff --git a/src/lib-dns/dns-util.h b/src/lib-dns/dns-util.h
new file mode 100644 (file)
index 0000000..cff52ff
--- /dev/null
+++ b/src/lib-dns/dns-util.h
@@ -0,0 +1,36 @@
+#ifndef DNS_UTIL_H
+#define DNS_UTIL_H 1
+
+static inline char
+dns_tolower(char c)
+{
+       if (c >= 'A' && c <= 'Z')
+               c+='a'-'A';
+       return c;
+}
+
+/**
+ * Will compare names in accordance with RFC4343
+ */
+int dns_compare(const char *a, const char *b) ATTR_PURE;
+int dns_ncompare(const char *a, const char *b, size_t n) ATTR_PURE;
+
+/**
+ * Same as above but done by labels from right to left
+ *
+ * www.example.org and www.example.net would be compared as
+ * org = net (return first difference)
+ * example = example
+ * www = www
+ */
+int dns_compare_labels(const char *a, const char *b) ATTR_PURE;
+
+/**
+ * Will match names in RFC4592 style
+ *
+ * this means *.foo.bar will match name.foo.bar
+ * but *DOES NOT* match something.name.foo.bar
+ */
+int dns_match_wildcard(const char *name, const char *mask) ATTR_PURE;
+
+#endif