c++ overflow problem Post: 302256213

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Top Forums Programming c++ overflow problem Post 302256213 by mshindo on Saturday 8th of November 2008 07:29:07 PM

11-08-2008

Registered User

c++ overflow problem

I have come accross a rather strange problem with two buffers that seem to be overriding each other.

Code:

bool killSession(const Session &session){
//Get user
	FILE* fp = fopen("conf/sessions.current", "rt");
	char line[1024]; char user[1024]; int x = 0; int leaseTime;
	printf("key: %s \n" , session.macAddress);

	while(fgets(line, 1024, fp) != NULL){
			x++;	
			int id; char addr[1024];
			sscanf(line, "%i %s %s %i", &id, addr, user, &leaseTime);
			addr[17] = '\0';
			
			printf("key: %s \naddr: %s \n", session.macAddress, addr);
			
			if(strcmp(addr, session.macAddress) != 0){
				printf("mac address found in file: %s \n", line);
				int gid =  getGroupId(user);
				char* accessType =  checkAccessType(gid);
				//modifyFirewall(accessType, session.macAddress, 0);
				break;
			}
		}
	//Finally remove session from session.current
	deleteLine("conf/sessions.current", x);
	fclose(fp);
return true;
}

gives the output:

Code:

key: 00:13:A9:A5:5D:EF 
key: 00:10 fakesessionthat michael 1999999999
 
addr: fakesessionthat 
mac address found in file: 0 fakesessionthat michael 1999999999

From that output it would seem that in the while loop that reads the session file session.macAddress is getting replaced by a part of the line variable. Have I actually managed to buffer overflow my own program.

Can someone please explain how ive gone wrong.

Thankyou

Cheers

mshindo

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LEARN ABOUT DEBIAN

sb2-session

sb2-session(1)						       sb2-session man page						    sb2-session(1)

NAME

       sb2-session - manage scratchbox2 sessions

SYNOPSIS

       sb2-session [COMMAND [PARAMS]]

DESCRIPTION

       sb2-session  is	used  to  create attachable scratchbox2 sessions.  You can save session even when you haven't done '-S session' during sb2
       startup.

       Note that you can give parameters to attach command which are passed verbatim to sb2. If there  is  only  one  session  to  attach,  it	is
       selected automatically.

       If no command is given, help text is printed.

COMMANDS

       help   shows help text

       save   saves current session

       list   lists detached sb2 sessions

       delete SESSION
	      deletes given session

       attach [SESSION [PARAMS]]
	      attaches to a given session

       setenv VARIABLE VALUE
	      store a value for an environment variable

       showenv
	      show stored environment variables

EXAMPLES

       Basic usage is:

	   [SB2 .. ] $ sb2-session save  # save session
	   [SB2 .. ] $ ^D		 # exit

       Later we can then attach to this session:

	   % sb2-session attach

       If there are more than one saved session, then:

	   % sb2-session list
	   session.XXXX    TARGET_ARM	   My Comment
	   session.YYYY    TARGET_ARM	   My Comment 2
	   session.ZZZZ    TARGET_MIPS
	   % sb2-session attach session.YYYY

       Here we pass '-eR' to sb2 and we only have one saved session:

	    % sb2-session attach -- -eR

       '--' marks end of parameter list for sb2-session.

       setenv  VARIABLE  VALUE	can  be  used  to  add environment variables, that will become active when a saved session is later taken into use
       (either by sb2-session attach or by sb2 -J).

       setenv VARIABLE VALUE does not change environment of sessions that are already active.

       showenv lists environment variable settings which have been stored with this tool. It  does  not  show  environment  variables  from  other
       sources.

SEE ALSO

       sb2(1)

AUTHOR

       Mika Westerberg

2.2								 21 December 2010						    sb2-session(1)