Commit message: Avoid reading past the end of buffer (Rui Reis)
CVE: CVE-2018-10360
CWE: CWE-125
Vulnerability description: The do_core_note function in readelf.c in libmagic.a in file 5.33 allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via a crafted ELF file.

Project: file

do_core_note(struct magic_set *ms, unsigned char *nbuf, uint32_t type,
    int swap, uint32_t namesz, uint32_t descsz,
    size_t noff, size_t doff, int *flags, size_t size, int clazz)
{
#ifdef ELFCORE
	int os_style = -1;
	/*
	 * Sigh.  The 2.0.36 kernel in Debian 2.1, at
	 * least, doesn't correctly implement name
	 * sections, in core dumps, as specified by
	 * the "Program Linking" section of "UNIX(R) System
	 * V Release 4 Programmer's Guide: ANSI C and
	 * Programming Support Tools", because my copy
	 * clearly says "The first 'namesz' bytes in 'name'
	 * contain a *null-terminated* [emphasis mine]
	 * character representation of the entry's owner
	 * or originator", but the 2.0.36 kernel code
	 * doesn't include the terminating null in the
	 * name....
	 */
	if ((namesz == 4 && strncmp((char *)&nbuf[noff], "CORE", 4) == 0) ||
	    (namesz == 5 && strcmp((char *)&nbuf[noff], "CORE") == 0)) {
		os_style = OS_STYLE_SVR4;
	} 

	if ((namesz == 8 && strcmp((char *)&nbuf[noff], "FreeBSD") == 0)) {
		os_style = OS_STYLE_FREEBSD;
	}

	if ((namesz >= 11 && strncmp((char *)&nbuf[noff], "NetBSD-CORE", 11)
	    == 0)) {
		os_style = OS_STYLE_NETBSD;
	}

	if (os_style != -1 && (*flags & FLAGS_DID_CORE_STYLE) == 0) {
		if (file_printf(ms, ", %s-style", os_style_names[os_style])
		    == -1)
			return 1;
		*flags |= FLAGS_DID_CORE_STYLE;
		*flags |= os_style;
	}

	switch (os_style) {
	case OS_STYLE_NETBSD:
		if (type == NT_NETBSD_CORE_PROCINFO) {
			char sbuf[512];
			struct NetBSD_elfcore_procinfo pi;
			memset(&pi, 0, sizeof(pi));
			memcpy(&pi, nbuf + doff, descsz);

			if (file_printf(ms, ", from '%.31s', pid=%u, uid=%u, "
			    "gid=%u, nlwps=%u, lwp=%u (signal %u/code %u)",
			    file_printable(sbuf, sizeof(sbuf),
			    CAST(char *, pi.cpi_name)),
			    elf_getu32(swap, (uint32_t)pi.cpi_pid),
			    elf_getu32(swap, pi.cpi_euid),
			    elf_getu32(swap, pi.cpi_egid),
			    elf_getu32(swap, pi.cpi_nlwps),
			    elf_getu32(swap, (uint32_t)pi.cpi_siglwp),
			    elf_getu32(swap, pi.cpi_signo),
			    elf_getu32(swap, pi.cpi_sigcode)) == -1)
				return 1;

			*flags |= FLAGS_DID_CORE;
			return 1;
		}
		break;

	default:
		if (type == NT_PRPSINFO && *flags & FLAGS_IS_CORE) {
			size_t i, j;
			unsigned char c;
			/*
			 * Extract the program name.  We assume
			 * it to be 16 characters (that's what it
			 * is in SunOS 5.x and Linux).
			 *
			 * Unfortunately, it's at a different offset
			 * in various OSes, so try multiple offsets.
			 * If the characters aren't all printable,
			 * reject it.
			 */
			for (i = 0; i < NOFFSETS; i++) {
				unsigned char *cname, *cp;
				size_t reloffset = prpsoffsets(i);
				size_t noffset = doff + reloffset;
				size_t k;
				for (j = 0; j < 16; j++, noffset++,
				    reloffset++) {
					/*
					 * Make sure we're not past
					 * the end of the buffer; if
					 * we are, just give up.
					 */
					if (noffset >= size)
						goto tryanother;

					/*
					 * Make sure we're not past
					 * the end of the contents;
					 * if we are, this obviously
					 * isn't the right offset.
					 */
					if (reloffset >= descsz)
						goto tryanother;

					c = nbuf[noffset];
					if (c == '\0') {
						/*
						 * A '\0' at the
						 * beginning is
						 * obviously wrong.
						 * Any other '\0'
						 * means we're done.
						 */
						if (j == 0)
							goto tryanother;
						else
							break;
					} else {
						/*
						 * A nonprintable
						 * character is also
						 * wrong.
						 */
						if (!isprint(c) || isquote(c))
							goto tryanother;
					}
				}
				/*
				 * Well, that worked.
				 */

				/*
				 * Try next offsets, in case this match is
				 * in the middle of a string.
				 */
				for (k = i + 1 ; k < NOFFSETS; k++) {
					size_t no;
					int adjust = 1;
					if (prpsoffsets(k) >= prpsoffsets(i))
						continue;
					for (no = doff + prpsoffsets(k);
					     no < doff + prpsoffsets(i); no++)
						adjust = adjust
						         && isprint(nbuf[no]);
					if (adjust)
						i = k;
				}
 
 				cname = (unsigned char *)
 				    &nbuf[doff + prpsoffsets(i)];
				for (cp = cname; cp < nbuf + size && *cp
				    && isprint(*cp); cp++)
 					continue;
 				/*
 				 * Linux apparently appends a space at the end
				 * of the command line: remove it.
				 */
				while (cp > cname && isspace(cp[-1]))
					cp--;
				if (file_printf(ms, ", from '%.*s'",
				    (int)(cp - cname), cname) == -1)
					return 1;
				*flags |= FLAGS_DID_CORE;
				return 1;

			tryanother:
				;
			}
		}
		break;
	}
#endif
	return 0;
}