1 files changed, 141 insertions, 0 deletions
diff --git a/src/dnsstub/dns_rcrw.c b/src/dnsstub/dns_rcrw.c
new file mode 100644
index 0000000..c0cad86
--- /dev/null
+++ b/src/dnsstub/dns_rcrw.c
@@ -0,0 +1,141 @@
+#include <unistd.h>
+#include "taia.h"
+#include "env.h"
+#include "byte.h"
+#include "str.h"
+#include "readclose.h"
+#include "dnsresolv.h"
+
+/**
+	* @file dns_rcrw.c
+	* @author djb
+	* @ref ucspi-tcp
+	* @brief DNS receive rewrite
+  */
+
+static stralloc data = {0};
+
+static int init(stralloc *rules)
+{
+  char host[256];
+  const char *x;
+  int i;
+  int j;
+  int k;
+
+  if (!stralloc_copys(rules,"")) return DNS_MEM;
+
+  x = env_get("DNSREWRITEFILE");
+  if (!x) x = "/etc/dnsrewrite";
+
+  i = openreadclose(x,&data,64);
+  if (i == -1) return DNS_INT;
+
+  if (i) {
+    if (!stralloc_append(&data,"\n")) return DNS_MEM;
+    i = 0;
+    for (j = 0; j < data.len; ++j)
+      if (data.s[j] == '\n') {
+        if (!stralloc_catb(rules,data.s + i,j - i)) return DNS_MEM;
+        while (rules->len) {
+          if (rules->s[rules->len - 1] != ' ')
+          if (rules->s[rules->len - 1] != '\t')
+          if (rules->s[rules->len - 1] != '\r')
+            break;
+          --rules->len;
+        }
+        if (!stralloc_0(rules)) return DNS_MEM;
+        i = j + 1;
+      }
+    return 0;
+  }
+
+  x = env_get("LOCALDOMAIN");
+  if (x) {
+    if (!stralloc_copys(&data,x)) return DNS_MEM;
+    if (!stralloc_append(&data," ")) return DNS_MEM;
+    if (!stralloc_copys(rules,"?:")) return DNS_MEM;
+    i = 0;
+    for (j = 0; j < data.len; ++j)
+      if (data.s[j] == ' ') {
+        if (!stralloc_cats(rules,"+.")) return DNS_MEM;
+        if (!stralloc_catb(rules,data.s + i,j - i)) return DNS_MEM;
+        i = j + 1;
+      }
+    if (!stralloc_0(rules)) return DNS_MEM;
+    if (!stralloc_cats(rules,"*.:")) return DNS_MEM;
+    if (!stralloc_0(rules)) return DNS_MEM;
+    return 0;
+  }
+
+  i = openreadclose("/etc/resolv.conf",&data,64);
+  if (i == -1) return DNS_INT;
+
+  if (i) {
+    if (!stralloc_append(&data,"\n")) return DNS_MEM;
+    i = 0;
+    for (j = 0; j < data.len; ++j)
+      if (data.s[j] == '\n') {
+        if (byte_equal("search ",7,data.s + i) || 
+            byte_equal("search\t",7,data.s + i) || 
+            byte_equal("domain ",7,data.s + i) || 
+            byte_equal("domain\t",7,data.s + i)) {
+          if (!stralloc_copys(rules,"?:")) return DNS_MEM;
+          i += 7;
+          while (i < j) {
+            k = byte_chr(data.s + i,j - i,' ');
+            k = byte_chr(data.s + i,k,'\t');
+            if (!k) { ++i; continue; }
+            if (!stralloc_cats(rules,"+.")) return DNS_MEM;
+            if (!stralloc_catb(rules,data.s + i,k)) return DNS_MEM;
+            i += k;
+          }
+          if (!stralloc_0(rules)) return DNS_MEM;
+          if (!stralloc_cats(rules,"*.:")) return DNS_MEM;
+          if (!stralloc_0(rules)) return DNS_MEM;
+          return 0;
+        }
+        i = j + 1;
+      }
+  }
+
+  host[0] = 0;
+  if (gethostname(host,sizeof(host)) == -1) return DNS_ERR;
+  host[(sizeof(host)) - 1] = 0;
+  i = str_chr(host,'.');
+  if (host[i]) {
+    if (!stralloc_copys(rules,"?:")) return DNS_MEM;
+    if (!stralloc_cats(rules,host + i)) return DNS_MEM;
+    if (!stralloc_0(rules)) return DNS_MEM;
+  }
+  if (!stralloc_cats(rules,"*.:")) return DNS_MEM;
+  if (!stralloc_0(rules)) return DNS_MEM;
+
+  return 0;
+}
+
+static int ok = 0;
+static unsigned int uses;
+static struct taia deadline;
+static stralloc rules = {0}; /* defined if ok */
+
+int dns_resolvconfrewrite(stralloc *out)
+{
+  struct taia now;
+
+  taia_now(&now);
+  if (taia_less(&deadline,&now)) ok = 0;
+  if (!uses) ok = 0;
+
+  if (!ok) {
+    if (init(&rules) < 0) return DNS_INT;
+    taia_uint(&deadline,600);
+    taia_add(&deadline,&now,&deadline);
+    uses = 10000;
+    ok = 1;
+  }
+
+  --uses;
+  if (!stralloc_copy(out,&rules)) return DNS_MEM;
+  return 0;
+}