[UNIX] Cyrus Sieve / libSieve Buffer Overflow
From: support@securiteam.com
Date: 12/05/02
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From: support@securiteam.com To: list@securiteam.com Date: 5 Dec 2002 21:02:26 +0200
The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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Cyrus Sieve / libSieve Buffer Overflow
------------------------------------------------------------------------
SUMMARY
Cyrus' Sieve implementation has been found to contain multiple buffer
overflow vulnerabilities. These overflows allow remote attackers to cause
the program to execute arbitrary code.
DETAILS
Vulnerable systems:
* Versions up to libSieve 2.1.2 and Cyrus IMAP 2.1.10 are affected.
Cyrus' Sieve implementation contains a couple of classic string based
buffer overflows in script parsing code. Anyone who can execute Sieve
scripts can exploit these bugs.
Note that with Cyrus IMAP server exploiting this gives you the privileges
of Cyrus user, capable of reading all users mails.
Problem comes when giving the script a >100 chars long corrupted header
name, >100 chars long IMAP flag or a script that contains lots of errors
to overflow the 500 char limit in error message.
Fix:
Apply the included patch. Note that this changes only the yacc files, you
still need to generate .c files from them. libSieve 2.1.3 will hopefully
also contain some more hardening against potential buffer overflows.
diff -ru cyrus-imapd-2.1.10-old/sieve/addr.y
cyrus-imapd-2.1.10/sieve/addr.y
--- cyrus-imapd-2.1.10-old/sieve/addr.y 2002-10-28 18:30:18.000000000
+0200
+++ cyrus-imapd-2.1.10/sieve/addr.y 2002-12-02 04:52:58.000000000 +0200
@@ -82,8 +82,9 @@
/* copy address error message into buffer provided by sieve parser */
int yyerror(char *s)
{
-extern char addrerr[];
+extern char addrerr[512];
- strcpy(addrerr, s);
+ strncpy(addrerr, s, sizeof(addrerr)-1);
+ addrerr[sizeof(addrerr)-1] = '\0';
return 0;
}
diff -ru cyrus-imapd-2.1.10-old/sieve/sieve.y
cyrus-imapd-2.1.10/sieve/sieve.y
--- cyrus-imapd-2.1.10-old/sieve/sieve.y 2002-05-14 19:51:50.000000000
+0300
+++ cyrus-imapd-2.1.10/sieve/sieve.y 2002-12-02 03:57:17.000000000 +0200
@@ -810,7 +810,7 @@
addrptr = s;
addrerr[0] = '\0'; /* paranoia */
if (addrparse()) {
- sprintf(errbuf, "address '%s': %s", s, addrerr);
+ snprintf(errbuf, sizeof(errbuf), "address '%s': %s", s, addrerr);
yyerror(errbuf);
return 0;
}
@@ -835,7 +835,7 @@
; controls, SP, and
; ":". */
if (!((*h >= 33 && *h <= 57) || (*h >= 59 && *h <= 126))) {
- sprintf(errbuf, "header '%s': not a valid header", hdr);
+ snprintf(errbuf, sizeof(errbuf), "header '%s': not a valid header",
hdr);
yyerror(errbuf);
return 0;
}
@@ -853,14 +853,14 @@
if (strcmp(f, "\\seen") && strcmp(f, "\\answered") &&
strcmp(f, "\\flagged") && strcmp(f, "\\draft") &&
strcmp(f, "\\deleted")) {
- sprintf(errbuf, "flag '%s': not a system flag", f);
+ snprintf(errbuf, sizeof(errbuf), "flag '%s': not a system flag", f);
yyerror(errbuf);
return 0;
}
return 1;
}
if (!imparse_isatom(f)) {
- sprintf(errbuf, "flag '%s': not a valid keyword", f);
+ snprintf(errbuf, sizeof(errbuf), "flag '%s': not a valid keyword", f);
yyerror(errbuf);
return 0;
}
ADDITIONAL INFORMATION
The information has been provided by <mailto:tss@iki.fi> Timo Sirainen.
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