1 files changed, 85 insertions, 0 deletions
diff --git a/src/dnsstub/dns_packet.c b/src/dnsstub/dns_packet.c
new file mode 100644
index 0000000..b131635
--- /dev/null
+++ b/src/dnsstub/dns_packet.c
@@ -0,0 +1,85 @@
+#include "error.h"
+#include "dnsresolv.h"
+
+/**
+	* @file dns_packet.c
+	* @author djb
+	* @ref ucspi-tcp
+	* @brief DNS low level packet routine
+	* @brief DNS should have used LZ77 instead of its own sophomoric compression algorithm.
+  */
+
+unsigned int dns_packet_copy(const char *buf,unsigned int len,unsigned int pos,char *out,unsigned int outlen)
+{
+  while (outlen) {
+    if (pos >= len) { errno = EPROTO; return 0; }
+    *out = buf[pos++];
+    ++out; --outlen;
+  }
+  return pos;
+}
+
+unsigned int dns_packet_skipname(const char *buf,unsigned int len,unsigned int pos)
+{
+  unsigned char ch;
+
+  for (;;) {
+    if (pos >= len) break;
+    ch = buf[pos++];
+    if (ch >= 192) return pos + 1;
+    if (ch >= 64) break;
+    if (!ch) return pos;
+    pos += ch;
+  }
+
+  errno = EPROTO;
+  return 0;
+}
+
+unsigned int dns_packet_getname(const char *buf,unsigned int len,unsigned int pos,char **d)
+{
+  unsigned int loop = 0;
+  unsigned int state = 0;
+  unsigned int firstcompress = 0;
+  unsigned int where;
+  unsigned char ch;
+  char name[255];
+  unsigned int namelen = 0;
+
+  for (;;) {
+    if (pos >= len) goto PROTO; 
+    ch = buf[pos++];
+    if (++loop >= 1000) goto PROTO;
+
+    if (state) {
+      if (namelen + 1 > sizeof(name)) goto PROTO; 
+      name[namelen++] = ch;
+      --state;
+    } else {
+      while (ch >= 192) {
+        where = ch; where -= 192; where <<= 8;
+        if (pos >= len) goto PROTO; 
+        ch = buf[pos++];
+        if (!firstcompress) firstcompress = pos;
+        pos = where + ch;
+        if (pos >= len) goto PROTO; 
+        ch = buf[pos++];
+        if (++loop >= 1000) goto PROTO;
+      }
+      if (ch >= 64) goto PROTO;
+      if (namelen + 1 > sizeof(name)) goto PROTO; 
+      name[namelen++] = ch;
+      if (!ch) break;
+      state = ch;
+    }
+  }
+
+  if (!dns_domain_copy(d,name)) return 0;
+
+  if (firstcompress) return firstcompress;
+  return pos;
+
+  PROTO:
+  errno = EPROTO;
+  return 0;
+}