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Name  : Avinash Ravi
uname : avinravi

Name  : Sravya Gudipudi
uname : sgudipud


What's in the code?
The main objective  of this project is  to scan various ports on a specified ip/ip's and derive
conclusions on the scanned ports. 
The implementation of PortScanner is as follows:

As the program starts, it parses  the command line arguments and creates a job queue with ip+port 
values in the queue. It then starts a thread to capture all the  incoming packets using libpcap  
and stores it in a map.  Then it starts a thread/threads to perform scanning using TCP SYN, TCP 
NULL,  TCP ACK, TCP FIN,  TCP XMAS, UDP scans on the ports of the specified host. These threads
pick up the work  from the job queue.For every scan,  it creates a  packet by populating the IP 
and TCP header values and calculates the TCP and IP header checksums. Now a raw socket connection 
is  opened and the manually  created packet is sent to the destination. Once the packet is sent, 
it keeps checking libpcap  instance for  any packet  received  from the destination until a time 
out occurs. If no packet is received, it then retransmits the packet and waits for response. The 
program retransmits a  packet for  three times  and if no response is received from the host, it 
moves onto the next port. If a response is seen  in libpcap instance, it checks the TCP/ICMP/UDP 
header to derive the conclusion based on the response received. Once all the specified scans are 
performed, it derives a conclusion based on all the responses received. The same process is repeated 
for all the  ports of  all the specified hosts. Once all the scanning is complete, final results 
are printed.

To scan a  DNS port using UDP scan, DNS headers are created manually and DNS specific payload is
added to the packet and sent over datagram sockets.  It also verifies if SSH, HTTP, SMTP, POP, IMAP
, WHOIS are running the expected  services by  sending appropriate queries over datagram sockets
and analysing the responses.

Tasks Accomplished
-> Running a background thread to capture all incoming packets using libpcap.
-> Performing TCP SYN, NULL, FIN, XMAS, ACK and UDP scans.
-> Sending manually created packets to scan the ports on the destination.
-> Parsing IP, TCP, UDP, ICMP headers of the received packets to analyse the response from hosts.
-> Deriving conclusion on a port of a host based on the results obtained from different scans.
-> Verifying if HTTP, SSH, SMTP, POP, IMAP and WHOIS are running these services on their respective ports.

Files in the Project
ps_setup.cpp      :      Contains setup code, such as parsing arguments
ps_setup.h        :      Header file for ps_setup

ps_helper.cpp     :      Contains hard coded values of port names of 1 - 1-24 ports
ps_helper.h       :      Header file for ps_helper

ps_lib.cpp        :      Contains functions necessary to support portScanner 
ps_lib.h          :      Header file for ps_lib

ps_pcap.cpp       :      Contains code to start a libpcap instance and capture incoming packets
ps_pcap.h         :      Header file for ps_pcap

portScanner.cpp   :      Contains code for creating threads and scanning ports 

Compiling the Code
The code compilation can be done using the Makefile as 
  gmake all
When compiling using gmake, the executable is stored in portScanner.

Execution and Interpretation of Output
This program can be executed as 
./portScanner --ip <ip_address> --ports <ports to scan> --prefix <Ip Prefix to scan> --file <FileName> --speedup <no_of_threads> --scan <scan_options>
Eg: ./portScanner --ip --ports 22-53 --speedup 5 --scan UDP SYN ACK

Here, FileName is the name of the file that contains a list of ip addresses.
One of ip, prefix, file options must be specified. All the other options are optional. 
If no ports are specified, 1-1024 ports are scanned by default.
All the scans are performed unless a scan option is specified.
By default, only a single instance of program scans the ports. If the speedup option is 
specified, it creates the no of threads specified in speedup option. This program limits 
the maximum number of threads to be specified in speedup option to 30.