Patch for 'ftp.c' file of ncftp v.2.3.5 to use within AWS instances

ftp.c.patch

--- libncftp/ftp.c.orig	2009-10-23 23:31:22.000000000 +0000
+++ libncftp/ftp.c	2015-08-15 19:49:04.014889944 +0000
@@ -5,6 +5,73 @@
  *
  */
 
+#include <stdio.h>
+#include <stdlib.h>
+#include <curl/curl.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <errno.h>
+#include <netdb.h>
+#include <arpa/inet.h>
+
+#define AWS_PUBLIC_IPV4_ADDRESS_URL "http://169.254.169.254/latest/meta-data/public-ipv4"
+
+struct MemoryStruct {
+  char *memory;
+  size_t size;
+};
+
+static size_t
+WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
+{
+	size_t realsize = size * nmemb;
+	struct MemoryStruct *mem = (struct MemoryStruct *)userp;
+
+	mem->memory = realloc(mem->memory, mem->size + realsize + 1);
+	if(mem->memory == NULL) { return 1; }
+
+	memcpy(&(mem->memory[mem->size]), contents, realsize);
+	mem->size += realsize;
+	mem->memory[mem->size] = 0;
+
+	return realsize;
+}
+
+int hostname_to_ip (char *hostname , char *ip)
+{
+	struct hostent *he;
+	struct in_addr **addr_list;
+	int i;
+         
+	if ((he=gethostbyname(hostname))==NULL) { return 0; }
+	addr_list=(struct in_addr **) he->h_addr_list;
+	for(i=0;addr_list[i]!=NULL;i++) { strcpy(ip, inet_ntoa(*addr_list[i]) ); return 1; }
+	return 0;
+}
+
+int is_a_private_ip (char *the_ip)
+{
+	char *ip_number;
+	int i=0,value[4];
+
+	for (i=0;i<4;i++) { value[i]=0; }
+	ip_number = strtok (the_ip,".");
+
+	i=0;
+	while ((ip_number!=NULL)&&(i<4)) { value[i++]=atoi(ip_number); ip_number=strtok (NULL, "."); }
+
+	if ((value[0]==127)||(value[0]==10)) { return 1; }
+	if ((value[0]==192)&&(value[1]==168)) { return 1; }
+	if ((value[0]==169)&&(value[1]==254)) { return 1; }
+	if ((value[0]==172)&&(value[1]>=16)&&(value[1]<=31)) { return 1; }
+	return 0;
+}
+
+int valid_ip (int *ip)
+{
+	if ((ip[0]>0)&&(ip[1]>0)&&(ip[2]>0)&&(ip[3]>0)&&(ip[0]<256)&&(ip[1]<256)&&(ip[2]<256)&&(ip[3]<256)) { return 1; } else { return 0; }
+}
+
 #include "syshdrs.h"
 #ifdef PRAGMA_HDRSTOP
 #	pragma hdrstop
@@ -743,9 +810,9 @@
 int
 FTPSendPort(const FTPCIPtr cip, struct sockaddr_in *saddr)
 {
-	char *a, *p;
-	int result;
 	ResponsePtr rp;
+	char *a, *p, the_ip[128];
+	int i=0,use_default=1,ext_aws_ipv4[4],result,resolv;
 
 	rp = InitResponse();
 	if (rp == NULL) {
@@ -762,8 +829,50 @@
 	/* Need to tell the other side which host (the address) and
 	 * which process (port) on that host to send data to.
 	 */
-	result = RCmd(cip, rp, "PORT %d,%d,%d,%d,%d,%d",
-		UC(a[0]), UC(a[1]), UC(a[2]), UC(a[3]), UC(p[0]), UC(p[1]));
+
+	CURL *curl_handle;
+	CURLcode res;
+
+	struct MemoryStruct chunk;
+
+	chunk.memory = malloc(1);
+	chunk.size = 0;
+
+	curl_global_init(CURL_GLOBAL_ALL);
+	curl_handle = curl_easy_init();
+	curl_easy_setopt(curl_handle, CURLOPT_TIMEOUT_MS, 5000L);
+	curl_easy_setopt(curl_handle, CURLOPT_URL, AWS_PUBLIC_IPV4_ADDRESS_URL);
+	curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
+	curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
+	curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
+
+	res=curl_easy_perform(curl_handle);
+	resolv=hostname_to_ip(cip->host, the_ip);
+
+	if((res==CURLE_OK)&&(chunk.size>0)) {
+		char *ip_number;
+		
+		for (i=0;i<4;i++) { ext_aws_ipv4[i]=0; }
+		ip_number = strtok (chunk.memory,".");
+		
+		i=0;
+		while ((ip_number!=NULL)&&(i<4)) { ext_aws_ipv4[i++]=atoi(ip_number); ip_number = strtok (NULL, "."); }
+
+		if (valid_ip(ext_aws_ipv4)) { if (resolv) { if (!is_a_private_ip(the_ip)) { use_default=0; }}}
+		free(ip_number);
+	}
+
+	if (use_default) {
+		result = RCmd(cip, rp, "PORT %d,%d,%d,%d,%d,%d",
+			UC(a[0]), UC(a[1]), UC(a[2]), UC(a[3]), UC(p[0]), UC(p[1]));
+	} else {
+		result = RCmd(cip, rp, "PORT %d,%d,%d,%d,%d,%d",
+			ext_aws_ipv4[0], ext_aws_ipv4[1], ext_aws_ipv4[2], ext_aws_ipv4[3], UC(p[0]), UC(p[1]));
+	}
+
+	curl_easy_cleanup(curl_handle);
+	free(chunk.memory);
+	curl_global_cleanup();
 
 	DoneWithResponse(cip, rp);
 	if (result < 0) {