Commit message: Fix bug #68819 (Fileinfo on specific file causes spurious OOM and/or segfault)
CVE: CVE-2015-4604
CWE: CWE-20
Vulnerability description: The mget function in softmagic.c in file 5.x, as used in the Fileinfo component in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8, does not properly maintain a certain pointer relationship, which allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted string that is mishandled by a "Python script text executable" rule.

Project: php-src
File: softmagic.c


private int
mcopy(struct magic_set *ms, union VALUETYPE *p, int type, int indir,
    const unsigned char *s, uint32_t offset, size_t nbytes, struct magic *m)
{
	/*
	 * Note: FILE_SEARCH and FILE_REGEX do not actually copy
	 * anything, but setup pointers into the source
	 */
	if (indir == 0) {
		switch (type) {
		case FILE_SEARCH:
			ms->search.s = RCAST(const char *, s) + offset;
			ms->search.s_len = nbytes - offset;
			ms->search.offset = offset;
			return 0;

		case FILE_REGEX: {
			const char *b;
			const char *c;
			const char *last;	/* end of search region */
			const char *buf;	/* start of search region */
			const char *end;
			size_t lines, linecnt, bytecnt;

			linecnt = m->str_range;
			bytecnt = linecnt * 80;

			if (bytecnt == 0) {
				bytecnt = 8192;
			}
			if (bytecnt > nbytes) {
				bytecnt = nbytes;
			}
			if (offset > bytecnt) {
				offset = bytecnt;
			}
			if (s == NULL) {
				ms->search.s_len = 0;
				ms->search.s = NULL;
				return 0;
			}
			buf = RCAST(const char *, s) + offset;
			end = last = RCAST(const char *, s) + bytecnt;
			/* mget() guarantees buf <= last */
			for (lines = linecnt, b = buf; lines && b < end &&
			     ((b = CAST(const char *,
				 memchr(c = b, '\n', CAST(size_t, (end - b)))))
			     || (b = CAST(const char *,
				 memchr(c, '\r', CAST(size_t, (end - c))))));
			     lines--, b++) {
				last = b;
				if (b[0] == '\r' && b[1] == '\n')
					b++;
			}
			if (lines)
				last = RCAST(const char *, s) + bytecnt;

			ms->search.s = buf;
			ms->search.s_len = last - buf;
			ms->search.offset = offset;
			ms->search.rm_len = 0;
			return 0;
		}
		case FILE_BESTRING16:
		case FILE_LESTRING16: {
			const unsigned char *src = s + offset;
			const unsigned char *esrc = s + nbytes;
			char *dst = p->s;
			char *edst = &p->s[sizeof(p->s) - 1];

			if (type == FILE_BESTRING16)
				src++;

			/* check that offset is within range */
			if (offset >= nbytes) {
				file_magerror(ms, "invalid offset %u in mcopy()",
				    offset);
				return -1;
			}
			for (/*EMPTY*/; src < esrc; src += 2, dst++) {
				if (dst < edst)
					*dst = *src;
				else
					break;
				if (*dst == '\0') {
					if (type == FILE_BESTRING16 ?
					    *(src - 1) != '\0' :
					    *(src + 1) != '\0')
						*dst = ' ';
				}
			}
			*edst = '\0';
			return 0;
		}
		case FILE_STRING:	/* XXX - these two should not need */
		case FILE_PSTRING:	/* to copy anything, but do anyway. */
		default:
			break;
		}
	}

	if (offset >= nbytes) {
		(void)memset(p, '\0', sizeof(*p));
		return 0;
	}
	if (nbytes - offset < sizeof(*p))
		nbytes = nbytes - offset;
	else
		nbytes = sizeof(*p);

	(void)memcpy(p, s + offset, nbytes);

	/*
	 * the usefulness of padding with zeroes eludes me, it
	 * might even cause problems
	 */
	if (nbytes < sizeof(*p))
		(void)memset(((char *)(void *)p) + nbytes, '\0',
		    sizeof(*p) - nbytes);