Managing Privilege in Java

Creation Code 39 Extended in Java Managing Privilege
122 Managing Privilege
Code 39 Extended Drawer In Java
Using Barcode creator for Java Control to generate, create Code 39 Extended image in Java applications.
Example 123 Code from a simple FTP server
Barcode Maker In Java
Using Barcode drawer for Java Control to generate, create bar code image in Java applications.
chroot("/var/ftproot"); if (fgets(filename, sizeof(filename), network) != NULL) { if (filename[strlen(filename) - 1] == '\n') { filename[strlen(filename) - 1] = '\0'; } localfile = fopen(filename, "r"); while ((len = fread(buf, 1, sizeof(buf), localfile)) != EOF) { (void)fwrite(buf, 1, len, network); } }
Bar Code Recognizer In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
The code in Example 124 demonstrates the correct construction of a chroot jail It fixes all the problems listed
Code-39 Generator In Visual C#.NET
Using Barcode creator for VS .NET Control to generate, create Code 39 Extended image in Visual Studio .NET applications.
Example 124 Code from the simple FTP server in Example 123 rewritten to create a chroot jail correctly
Code 39 Full ASCII Creator In VS .NET
Using Barcode encoder for ASP.NET Control to generate, create Code-39 image in ASP.NET applications.
// close all open file descriptors for (int i = 0; i < sysconf(_SC_OPEN_MAX); i++) { if (close(i) != 0) { exit(-1); } } // call chroot, check for errors, // then immediately call chdir if ((chroot("/var/ftproot") != 0) || (chdir("/") != 0)) { exit(-1); } // drop privileges if (drop_priv_temp(getuid()) != 0) { exit(-1); } if (fgets(filename, sizeof(filename), network) != NULL) { if (filename[strlen(filename) - 1] == '\n') { filename[strlen(filename) - 1] = '\0'; } localfile = fopen(filename, "r"); while ((len = fread(buf, 1, sizeof(buf), localfile)) != EOF) { (void)fwrite(buf, 1, len, network) ; } }
Paint Code 3/9 In VS .NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Code 3 of 9 image in .NET framework applications.
12 Privileged Programs
Code 3/9 Generator In VB.NET
Using Barcode encoder for .NET framework Control to generate, create Code 3/9 image in VS .NET applications.
Beware of Unexpected Events General guidelines for handling unexpected and exceptional conditions take on even greater importance in privileged programs, where attacks are more likely and the cost of a successful exploit is greater Check for Every Error Condition Many initially mysterious bugs have eventually been traced back to a failed system call with an ignored return value Attackers often leverage unexpected conditions to violate programmers assumptions, which can be particularly dangerous in code that runs with privileges Software that will eventually run under different operating systems, operating system versions, hardware configurations, or runtime environments is even more likely to suffer from unexpected conditions If a function returns an error code or any other evidence of its success or failure, always check for error conditions, even if there is no obvious way for the error to occur Two dubious assumptions that are easy to spot in code are this function call can never fail and it doesn t matter if this function call fails When programmers ignore the return value from a function, they implicitly state that they are operating under one of these assumptions Even worse, when a return value is inspected but the response is inappropriate, the problem is often hidden among code that appears to handle failures Example 125 shows a vulnerable call to setuid() from Sendmail 8101 [Sendmail, 2001] that was identified due to a Linux capabilities bug that allowed attackers to cause setuid() to fail silently [Purczynski, 2000] If the call to setuid() fails, the programmer notes the failure and continues execution, which leaves Sendmail running as root when it expects to have dropped privileges
Draw Barcode In Java
Using Barcode encoder for Java Control to generate, create bar code image in Java applications.
Example 125 Code from Sendmail 8101 that fails to respond appropriately when setuid() fails
Generating EAN128 In Java
Using Barcode printer for Java Control to generate, create GS1-128 image in Java applications.
if (setuid(DefUid) < 0 && geteuid() == 0) syserr("prog_open: setuid(%ld) failed", (long) DefUid);
Drawing Bar Code In Java
Using Barcode generation for Java Control to generate, create bar code image in Java applications.
122 Managing Privilege
Data Matrix ECC200 Generator In Java
Using Barcode generator for Java Control to generate, create Data Matrix image in Java applications.
Example 126 demonstrates how the code was patched in Sendmail 8102 to include a more appropriate response to a failure when calling setuid(): a call to exit()
Code 3 Of 9 Creation In Java
Using Barcode generation for Java Control to generate, create Code 3/9 image in Java applications.
Example 126 Vulnerable code from Example 125 patched in Sendmail 8102 to call exit() when setuid() fails
Encode RoyalMail4SCC In Java
Using Barcode encoder for Java Control to generate, create Royal Mail Barcode image in Java applications.
if (setuid(DefUid) < 0 && geteuid() == 0) { syserr("prog_open: setuid(%ld) failed", (long) DefUid); exit(EX_TEMPFAIL); }
EAN13 Drawer In .NET Framework
Using Barcode drawer for ASP.NET Control to generate, create UPC - 13 image in ASP.NET applications.
Value Security over Robustness: Die on Errors Don't attempt to recover from unexpected or poorly understood errors When errors do occur, value security over robustness This means the program should either stop the action it is currently performing or halt entirely If there is reasonable evidence that an error occurred because of some malicious activity, do not provide the would-be attacker with the capability to interact with the program Doing so only increases the window of vulnerability and makes it easier for an attacker to track down some weakness in the program At the same time, always take care to fail securely If your program can exit in a state that exposes sensitive information or helps attackers in some other way, you ve made their job easier Disable Signals Before Acquiring Privileges Disable signals before elevating privileges to avoid having signal handling code run with privileges Re-enable signals after dropping back to standard user privileges Signal handlers and spawned processes run with the privileges of the owning process, so if a process is running as root when a signal fires or a subprocess is executed, the signal handler or subprocess will operate with root privileges Signal handling code should never require elevated privileges Of course, a well-written signal handler should be small enough and simple enough that it cannot cause errors when executed with privileges; reducing signal handlers to the minimum possible complexity is always a worthwhile goal Example 127 shows the code from Example 121 rewritten to disable signals while executing with privileges
Encode GS1-128 In VS .NET
Using Barcode creator for ASP.NET Control to generate, create EAN / UCC - 14 image in ASP.NET applications.
Draw Code 128 In VB.NET
Using Barcode generator for Visual Studio .NET Control to generate, create Code 128A image in .NET applications.
Encode Barcode In VS .NET
Using Barcode generation for ASP.NET Control to generate, create barcode image in ASP.NET applications.
Creating Barcode In Visual Studio .NET
Using Barcode generator for Visual Studio .NET Control to generate, create bar code image in .NET framework applications.