# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 1437057368 -32400
# Node ID 82d6a35cf432b66c4c7bdcbdc111a6eceb84b66f
# Parent  ebb5bb9bc32e1e75166cf134d2c1d6095143f710
parsers: fix buffer overflow by invalid parent revision read from revlog

If revlog file is corrupted, it can have parent pointing to invalid revision.
So we should validate it before updating nothead[], phases[], seen[], etc.
Otherwise it would cause segfault at best.

We could use "rev" instead of "maxrev" as upper bound, but I think the explicit
"maxrev" can clarify that we just want to avoid possible buffer overflow
vulnerability.

diff -r ebb5bb9bc32e -r 82d6a35cf432 mercurial/parsers.c
--- a/mercurial/parsers.c	Thu Jul 16 11:12:15 2015 -0700
+++ b/mercurial/parsers.c	Thu Jul 16 23:36:08 2015 +0900
@@ -752,8 +752,8 @@
 	return PyString_AS_STRING(self->data) + pos * v1_hdrsize;
 }
 
-static inline void index_get_parents(indexObject *self, Py_ssize_t rev,
-				int *ps)
+static inline int index_get_parents(indexObject *self, Py_ssize_t rev,
+				    int *ps, int maxrev)
 {
 	if (rev >= self->length - 1) {
 		PyObject *tuple = PyList_GET_ITEM(self->added,
@@ -765,6 +765,13 @@
 		ps[0] = getbe32(data + 24);
 		ps[1] = getbe32(data + 28);
 	}
+	/* If index file is corrupted, ps[] may point to invalid revisions. So
+	 * there is a risk of buffer overflow to trust them unconditionally. */
+	if (ps[0] > maxrev || ps[1] > maxrev) {
+		PyErr_SetString(PyExc_ValueError, "parent out of range");
+		return -1;
+	}
+	return 0;
 }
 
 
@@ -1149,7 +1156,8 @@
 	if (minrevallphases != -1) {
 		int parents[2];
 		for (i = minrevallphases; i < len; i++) {
-			index_get_parents(self, i, parents);
+			if (index_get_parents(self, i, parents, len - 1) < 0)
+				goto release_phasesetlist;
 			set_phase_from_parents(phases, parents[0], parents[1], i);
 		}
 	}
@@ -1248,7 +1256,8 @@
 			continue;
 		}
 
-		index_get_parents(self, i, parents);
+		if (index_get_parents(self, i, parents, len - 1) < 0)
+			goto bail;
 		for (j = 0; j < 2; j++) {
 			if (parents[j] >= 0)
 				nothead[parents[j]] = 1;
@@ -1716,7 +1725,8 @@
 				}
 			}
 		}
-		index_get_parents(self, v, parents);
+		if (index_get_parents(self, v, parents, maxrev) < 0)
+			goto bail;
 
 		for (i = 0; i < 2; i++) {
 			int p = parents[i];
@@ -1813,7 +1823,8 @@
 			continue;
 
 		sv = seen[v];
-		index_get_parents(self, v, parents);
+		if (index_get_parents(self, v, parents, maxrev) < 0)
+			goto bail;
 
 		for (i = 0; i < 2; i++) {
 			int p = parents[i];
diff -r ebb5bb9bc32e -r 82d6a35cf432 tests/test-parseindex.t
--- a/tests/test-parseindex.t	Thu Jul 16 11:12:15 2015 -0700
+++ b/tests/test-parseindex.t	Thu Jul 16 23:36:08 2015 +0900
@@ -59,3 +59,62 @@
   26333235a41c
 
   $ cd ..
+
+Test corrupted p1/p2 fields that could cause SEGV at parsers.c:
+
+  $ mkdir invalidparent
+  $ cd invalidparent
+
+  $ hg clone --pull -q --config phases.publish=False ../a limit
+  $ hg clone --pull -q --config phases.publish=False ../a segv
+  $ rm -R limit/.hg/cache segv/.hg/cache
+
+  $ python <<EOF
+  > data = open("limit/.hg/store/00changelog.i", "rb").read()
+  > for n, p in [('limit', '\0\0\0\x02'), ('segv', '\0\x01\0\0')]:
+  >     # corrupt p1 at rev0 and p2 at rev1
+  >     d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:]
+  >     open(n + "/.hg/store/00changelog.i", "wb").write(d)
+  > EOF
+
+  $ hg debugindex -f1 limit/.hg/store/00changelog.i
+     rev flag   offset   length     size   base   link     p1     p2       nodeid
+       0 0000        0       63       62      0      0      2     -1 7c31755bf9b5
+       1 0000       63       66       65      1      1      0      2 26333235a41c
+  $ hg debugindex -f1 segv/.hg/store/00changelog.i
+     rev flag   offset   length     size   base   link     p1     p2       nodeid
+       0 0000        0       63       62      0      0  65536     -1 7c31755bf9b5
+       1 0000       63       66       65      1      1      0  65536 26333235a41c
+
+  $ cat <<EOF > test.py
+  > import sys
+  > from mercurial import changelog, scmutil
+  > cl = changelog.changelog(scmutil.vfs(sys.argv[1]))
+  > n0, n1 = cl.node(0), cl.node(1)
+  > ops = [
+  >     ('compute_phases_map_sets', lambda: cl.computephases([[0], []])),
+  >     ('index_headrevs', lambda: cl.headrevs()),
+  >     ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)),
+  >     ('find_deepest', lambda: cl.ancestor(n0, n1)),
+  >     ]
+  > for l, f in ops:
+  >     print l + ':',
+  >     try:
+  >         f()
+  >         print 'uncaught buffer overflow?'
+  >     except ValueError, inst:
+  >         print inst
+  > EOF
+
+  $ python test.py limit/.hg/store
+  compute_phases_map_sets: parent out of range
+  index_headrevs: parent out of range
+  find_gca_candidates: parent out of range
+  find_deepest: parent out of range
+  $ python test.py segv/.hg/store
+  compute_phases_map_sets: parent out of range
+  index_headrevs: parent out of range
+  find_gca_candidates: parent out of range
+  find_deepest: parent out of range
+
+  $ cd ..