Security Issues with CGI in .NET framework

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Buffer overflow problems have recently been exploited in such popular network daemons as qpopper, named, wu-ftpd, and many others Candidates for the buffer overrun exploit can include older versions of ProFTPD and wu-ftp Due to insufficient bounds checking in these programs, it is possible to subvert an FTP server by corrupting its internal stack space By supplying carefully designed commands to the FTP server, intruders could force the server to execute arbitrary commands using root privilege Thus, intruders who are able to exploit this vulnerability can ultimately gain interactive access with root privilege to the remote FTP server The most vulnerable systems were the ones with the ftpd software installed and enabled by default One temporary solution to this attack is to disable any world-writable directories to which the user may have access by making them read-only This action will prevent an attacker from building an unusually large path, which is required to execute these particular attacks The other preferred solution is to upgrade the programs with patches that address the potential buffer overruns Of even more interest, CERT reported a buffer overrun in early 1998 in <cfg_getline()> that possibly allowed malicious users to gain access, not as root, but as the user of Apache This is all the more reason to run Apache as any non-privileged user, other than nobody Those using pre-125 versions of Apache are susceptible to this buffer overflow in <cfg_getline()> <cfg_getline()> is a function that the Apache core and several Apache modules use to read certain types of files from disk Some examples of the type of files that read with this are htaccess, htpasswd, and mod_imap files It is possible to create a sequence of data such that a buffer overflow occurs while <cfg_getline()> is reading from a file If someone has access to create any of these types of files on the server, that hole is generally exploitable to gain full access to the user that Apache runs as On most systems, this is of little consequence because many users already have such access If, however, the server is secured so that the user has no access to the server other than to create and modify files (for example, an FTP only account with no ability to create CGI scripts), this could allow increased access to the server
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Security Issues with CGI
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Because CGI scripts are executables, they are subject to the same security vulnerabilities as normal programs What makes CGI scripts especially
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dangerous is that anyone in the world with a Web browser and Internet connection can execute programs on any public Web server The first step in securing CGIs is to secure the server; Apache should be run as a non-trusted user with secure permissions on key files The real key to keeping CGI scripts safe is to eliminate vulnerabilities in them
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Most CGI programs perform system calls, such as reading from or writing to a disk file, or perhaps executing other programs If any of the variables passed to the CGI are used in formulating the parameters to these system calls, malicious users can manipulate them to do undesirable things Certain commands are very dangerous; the eval command is one of them eval lets a script execute an arbitrary command given in a variable A CGI script could take the name of the command to run as a parameter, execute it, and show the output This could give a system cracker all the ammunition necessary to break into a system
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Buffer Overruns
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C programs suffer from vulnerability to buffer overruns When C programs read data, they must allocate enough room in memory to hold it When more data is read in than room is available, the excess data can be executed as code If writing scripts in C, ensure they are free from buffer overruns by checking the amount of data that comes into the program Although this is relatively difficult to exploit, it is worth watching
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