adding some code to check DNS consistency

1 files changed, 88 insertions, 25 deletions

diff --git a/tools/greylist.c b/tools/greylist.c
index d76ba08..b64636e 100644
--- a/tools/greylist.c
+++ b/tools/greylist.c
@@ -3,7 +3,7 @@
 #include <iomanip>
 #include <string>
 
-#include <sys/types.h>          /* for stat() */
+#include <sys/types.h>          /* for stat(), getaddrinfo() */
 #include <sys/stat.h>           /* for stat() */
 #include <unistd.h>             /* for stat() */
 #include <stdio.h>              /* for perror */
@@ -17,6 +17,10 @@
 // requires apt-get install libboost-filesystem-dev:
 #include <boost/filesystem.hpp>
 
+#include <sys/socket.h>         /* for getaddrinfo() */
+#include <netdb.h>              /* for getaddrinfo() */
+#include <string.h>             /* for memset() */
+
 using namespace std;
 
 const int minute(60);
@@ -84,6 +88,8 @@ public:
   string progname;
   pid_t mypid;
   timeval now;
+  char* ipvar;
+  char* hostvar;
   string ipbase;
   string ipname;
   string hostname;
@@ -104,7 +110,8 @@ public:
 // access comes after modification:
   void update(const string msg, const timeval new_mod,
         const timeval new_ac, const int penalty=0);
-  void bind();
+  int setup();
+  int check_dns();
 };
 
 string basename(const string path){
@@ -113,11 +120,24 @@ string basename(const string path){
   return path;
 }
 
-void whatsit::bind(){
+int whatsit::setup(){
   stringstream foo;
-  foo << basename(progname) << suffix 
+  foo << basename(progname) << suffix
     << "[" << mypid << "]";
   progid = foo.str();
+
+  ipvar = getenv("TCPREMOTEIP");
+  if (!ipvar) {
+    cerr << progid
+      << " TCPREMOTEIP not set???" << endl;
+    // should never happen
+    // although you can make it happen using a weird test-harness
+    return(ex_syserr);
+  }
+  ipbase = ipvar;
+  hostvar = getenv("TCPREMOTEHOST");
+  if (hostvar) hostname = hostvar;
+  return 0;
 }
 
 string time_out(const int _ttt){
@@ -218,6 +238,7 @@ void whatsit::update(const string msg, const timeval new_mod,
   utimes(ipname.c_str(), upd);
 }
 
+
 int main(int _argc, char** _argv){
   mypid = getpid();
   int argc(_argc);
@@ -256,7 +277,7 @@ int main(int _argc, char** _argv){
       exeunt(ex_syserr);
     }
   }
-  foo.bind();
+  if (foo.setup()) return ex_syserr;
 
   if (scanmode) {
     scan(foo.progid, dirname, copies);
@@ -269,31 +290,15 @@ int main(int _argc, char** _argv){
 
 // check mode ... perform some extra checks.
 // Probably a better design would be to
-//  a) make more thorough DNS checks, and
-//  b) move all the DNS checking to a separate module
+//  (a) make more thorough DNS checks, and
+//  (b) move all the DNS checking to a separate module
 
-  char* hostvar = getenv("TCPREMOTEHOST");
-  if (!hostvar) {
-    cerr << foo.progid
-      << " from " << foo.ipbase
-      << " ... TCPREMOTEHOST not set???" << endl;
-    exeunt(ex_spam);
-  }
+  int dns = foo.check_dns();
+  if (dns == ex_syserr) return dns;
   exeunt(sts);
 }
 
 int whatsit::doit(const int penalty){
-  char* ipvar = getenv("TCPREMOTEIP");
-  if (!ipvar) {
-    cerr << progid
-      << " TCPREMOTEIP not set???" << endl;
-    // should never happen
-    // although you can make it happen using a weird test-harness
-    return(ex_syserr);
-  }
-  ipbase = ipvar;
-  char* hostvar = getenv("TCPREMOTEHOST");
-  if (hostvar) hostname = hostvar;
 
 // see if our directory exists:
   struct stat dirstat;
@@ -365,3 +370,61 @@ int whatsit::doit(const int penalty){
   update("returning customer", mod_orig, now, penalty);
   return 0;
 }
+
+int whatsit::check_dns(){
+  char* hostvar = getenv("TCPREMOTEHOST");
+  if (!hostvar) {
+    cerr << progid
+      << " from " << ipbase
+      << " ... TCPREMOTEHOST not set???" << endl;
+    exeunt(ex_spam);
+  }
+
+  struct addrinfo *result;
+  struct addrinfo *ipresult;
+  struct addrinfo *res;
+  addrinfo hints;
+  int error;
+
+  /* resolve the domain name into a list of addresses */
+  memset(&hints, 0, sizeof(struct addrinfo));
+#if 1
+  // restrict to TCP only; otherwise we get N records per address
+  hints.ai_protocol = IPPROTO_TCP;
+#endif
+  error = getaddrinfo(hostvar, NULL, &hints, &result);
+  if (error) {
+    cerr << "error in getaddrinfo for " << hostvar
+      << " : " << gai_strerror(error) << endl;
+    return ex_syserr;
+  }
+
+  error = getaddrinfo(ipvar, NULL, &hints, &ipresult);
+  if (error) {
+    cerr << "error in getaddrinfo for " << ipvar
+      << " : " << gai_strerror(error) << endl;
+    return ex_syserr;
+  }
+
+// loop over all returned results and check for a match.
+  for (res = result; res != NULL; res = res->ai_next){
+    void *numericAddress;
+
+    sa_family_t fam = ((sockaddr *)res->ai_addr)->sa_family;
+    int addrsize;
+    switch (fam) {
+    case AF_INET:
+      numericAddress = &(((sockaddr_in *)res->ai_addr)->sin_addr.s_addr);
+      addrsize = sizeof(in_addr);
+      break;
+    case AF_INET6:
+      numericAddress = &(((sockaddr_in6 *)res->ai_addr)->sin6_addr.s6_addr);
+      addrsize = sizeof(in6_addr);
+      break;
+    default:
+      cerr << "?Unknown address family " << fam << endl;
+      return(ex_syserr);
+    }
+  }
+  return 0;
+}