[Midnightbsd-cvs] src [6955] trunk: Fix a DOS attack on libmagic

[laffer1 at midnightbsd.org]

Revision: 6955
          http://svnweb.midnightbsd.org/src/?rev=6955
Author:   laffer1
Date:     2014-12-11 08:04:28 -0500 (Thu, 11 Dec 2014)
Log Message:
-----------
Fix a DOS attack on libmagic

Modified Paths:
--------------
    trunk/UPDATING
    trunk/contrib/file/elfclass.h
    trunk/contrib/file/readelf.c
    trunk/contrib/file/softmagic.c

Modified: trunk/UPDATING
===================================================================
--- trunk/UPDATING	2014-11-27 15:08:44 UTC (rev 6954)
+++ trunk/UPDATING	2014-12-11 13:04:28 UTC (rev 6955)
@@ -1,5 +1,10 @@
 Updating Information for MidnightBSD users.
 
+20141211:
+	Fix a security issue with file and libmagic that can allow
+	an attacker to create a denial of service attack on any
+	program that uses libmagic.
+
 20141117:
 	Add support for UDP Lite protocol aka RFC 3828 to IPv4 and IPv6
 	stacks.

Modified: trunk/contrib/file/elfclass.h
===================================================================
--- trunk/contrib/file/elfclass.h	2014-11-27 15:08:44 UTC (rev 6954)
+++ trunk/contrib/file/elfclass.h	2014-12-11 13:04:28 UTC (rev 6955)
@@ -35,10 +35,12 @@
 	switch (type) {
 #ifdef ELFCORE
 	case ET_CORE:
+		phnum = elf_getu16(swap, elfhdr.e_phnum);
+		if (phnum > MAX_PHNUM)
+			return toomany(ms, "program", phnum);
 		flags |= FLAGS_IS_CORE;
 		if (dophn_core(ms, clazz, swap, fd,
-		    (off_t)elf_getu(swap, elfhdr.e_phoff),
-		    elf_getu16(swap, elfhdr.e_phnum), 
+		    (off_t)elf_getu(swap, elfhdr.e_phoff), phnum,
 		    (size_t)elf_getu16(swap, elfhdr.e_phentsize),
 		    fsize, &flags) == -1)
 			return -1;
@@ -46,18 +48,24 @@
 #endif
 	case ET_EXEC:
 	case ET_DYN:
+		phnum = elf_getu16(swap, elfhdr.e_phnum);
+		if (phnum > MAX_PHNUM)
+			return toomany(ms, "program", phnum);
+		shnum = elf_getu16(swap, elfhdr.e_shnum);
+		if (shnum > MAX_SHNUM)
+			return toomany(ms, "section", shnum);
 		if (dophn_exec(ms, clazz, swap, fd,
-		    (off_t)elf_getu(swap, elfhdr.e_phoff),
-		    elf_getu16(swap, elfhdr.e_phnum), 
+		    (off_t)elf_getu(swap, elfhdr.e_phoff), phnum,
 		    (size_t)elf_getu16(swap, elfhdr.e_phentsize),
-		    fsize, &flags, elf_getu16(swap, elfhdr.e_shnum))
-		    == -1)
+		    fsize, &flags, shnum) == -1)
 			return -1;
 		/*FALLTHROUGH*/
 	case ET_REL:
+		shnum = elf_getu16(swap, elfhdr.e_shnum);
+		if (shnum > MAX_SHNUM)
+			return toomany(ms, "section", shnum);
 		if (doshn(ms, clazz, swap, fd,
-		    (off_t)elf_getu(swap, elfhdr.e_shoff),
-		    elf_getu16(swap, elfhdr.e_shnum),
+		    (off_t)elf_getu(swap, elfhdr.e_shoff), shnum,
 		    (size_t)elf_getu16(swap, elfhdr.e_shentsize),
 		    fsize, &flags, elf_getu16(swap, elfhdr.e_machine),
 		    (int)elf_getu16(swap, elfhdr.e_shstrndx)) == -1)

Modified: trunk/contrib/file/readelf.c
===================================================================
--- trunk/contrib/file/readelf.c	2014-11-27 15:08:44 UTC (rev 6954)
+++ trunk/contrib/file/readelf.c	2014-12-11 13:04:28 UTC (rev 6955)
@@ -60,6 +60,18 @@
 private uint32_t getu32(int, uint32_t);
 private uint64_t getu64(int, uint64_t);
 
+#define MAX_PHNUM	256
+#define	MAX_SHNUM	1024
+
+private int
+toomany(struct magic_set *ms, const char *name, uint16_t num)
+{
+	if (file_printf(ms, ", too many %s header sections (%u)", name, num
+	    ) == -1)
+		return -1;
+	return 0;
+}
+
 private uint16_t
 getu16(int swap, uint16_t value)
 {
@@ -492,13 +504,13 @@
 	if (namesz & 0x80000000) {
 	    (void)file_printf(ms, ", bad note name size 0x%lx",
 		(unsigned long)namesz);
-	    return offset;
+	    return 0;
 	}
 
 	if (descsz & 0x80000000) {
 	    (void)file_printf(ms, ", bad note description size 0x%lx",
 		(unsigned long)descsz);
-	    return offset;
+	    return 0;
 	}
 
 
@@ -900,6 +912,7 @@
 	Elf32_Shdr sh32;
 	Elf64_Shdr sh64;
 	int stripped = 1;
+	size_t nbadcap = 0;
 	void *nbuf;
 	off_t noff, coff, name_off;
 	uint64_t cap_hw1 = 0;	/* SunOS 5.x hardware capabilites */
@@ -977,6 +990,8 @@
 			free(nbuf);
 			break;
 		case SHT_SUNW_cap:
+			if (nbadcap > 5)
+                              break;
 			switch (mach) {
 			case EM_SPARC:
 			case EM_SPARCV9:
@@ -1053,6 +1068,8 @@
 					    (unsigned long long)xcap_tag,
 					    (unsigned long long)xcap_val) == -1)
 						return -1;
+					if (nbadcap++ > 2)
+						coff = xsh_size;
 					break;
 				}
 			}
@@ -1233,7 +1250,7 @@
 	int flags = 0;
 	Elf32_Ehdr elf32hdr;
 	Elf64_Ehdr elf64hdr;
-	uint16_t type;
+	uint16_t type, phnum, shnum;
 
 	if (ms->flags & (MAGIC_MIME|MAGIC_APPLE))
 		return 0;

Modified: trunk/contrib/file/softmagic.c
===================================================================
--- trunk/contrib/file/softmagic.c	2014-11-27 15:08:44 UTC (rev 6954)
+++ trunk/contrib/file/softmagic.c	2014-12-11 13:04:28 UTC (rev 6955)
@@ -67,6 +67,9 @@
 private void cvt_64(union VALUETYPE *, const struct magic *);
 
 #define OFFSET_OOB(n, o, i)	((n) < (o) || (i) > ((n) - (o)))
+
+#define MAX_RECURSION_LEVEL	10
+
 /*
  * softmagic - lookup one file in parsed, in-memory copy of database
  * Passed the name and FILE * of one file to be typed.
@@ -1200,7 +1203,7 @@
 	union VALUETYPE *p = &ms->ms_value;
 	struct mlist ml;
 
-	if (recursion_level >= 20) {
+	if (recursion_level >= MAX_RECURSION_LEVEL) {
 		file_error(ms, 0, "recursion nesting exceeded");
 		return -1;
 	}