1 files changed, 28 insertions, 0 deletions
diff --git a/src/network/dn_expand.c b/src/network/dn_expand.c
new file mode 100644
index 00000000..01b449bb
--- /dev/null
+++ b/src/network/dn_expand.c
@@ -0,0 +1,28 @@
+#include <resolv.h>
+#include <string.h>
+
+#define BITOP(a,b,op) \
+ ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
+
+int dn_expand(unsigned char *b, unsigned char *pz, unsigned char *p, unsigned char *s, int outlen)
+{
+	/* Remember jump destinations to detect loops and abort */
+	size_t seen[512/8/sizeof(size_t)] = { 0 };
+	unsigned char *sz = s + outlen;
+	if (pz-b > 512) return -1;
+	for (;;) {
+		if (p>=pz) return -1;
+		else if (*p&0xc0) {
+			int j = (p[0]&1) | p[1];
+			if (BITOP(seen, j, &)) return -1;
+			BITOP(seen, j, |=);
+			p = b + j;
+		} else if (*p) {
+			if (p+*p+1>=pz || s+*p>=sz) return -1;
+			memcpy(s, p+1, *p);
+			s += *p+1;
+			p += *p+1;
+			s[-1] = *p ? '.' : 0;
+		} else return 0;
+	}
+}