From dd726dcc6a95355d0e0cc949018d9c8aefc89a02 Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@gentoo.org>
Date: Mon, 24 Dec 2012 19:41:49 -0500
Subject: [PATCH 1/2] libsandbox: reject "" paths with *at funcs before
 checking the dirfd

When it comes to processing errors, an empty path is checked before
an invalid dirfd.  Make sure sandbox matches that behavior for the
random testsuites out there that look for this.

URL: https://bugs.gentoo.org/346929
Reported-by: Marien Zwart <marienz@gentoo.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
 libsandbox/wrapper-funcs/__pre_check.c        |  2 ++
 libsandbox/wrapper-funcs/mkdirat_pre_check.c  | 17 +++++------------
 libsandbox/wrapper-funcs/openat_pre_check.c   | 15 ++++-----------
 libsandbox/wrapper-funcs/unlinkat_pre_check.c | 17 +++++------------
 libsandbox/wrappers.h                         |  2 ++
 tests/mkdirat-3.sh                            |  7 +++++++
 tests/mkdirat.at                              |  1 +
 tests/openat-2.sh                             |  9 +++++++++
 tests/openat.at                               |  1 +
 tests/unlinkat-4.sh                           |  7 +++++++
 tests/unlinkat.at                             |  1 +
 11 files changed, 44 insertions(+), 35 deletions(-)
 create mode 100755 tests/mkdirat-3.sh
 create mode 100755 tests/openat-2.sh
 create mode 100755 tests/unlinkat-4.sh

diff --git a/libsandbox/wrapper-funcs/__pre_check.c b/libsandbox/wrapper-funcs/__pre_check.c
index 2d5711f..28ad91f 100644
--- a/libsandbox/wrapper-funcs/__pre_check.c
+++ b/libsandbox/wrapper-funcs/__pre_check.c
@@ -20,3 +20,5 @@
 #if SB_NR_UNLINK != SB_NR_UNDEF && SB_NR_UNLINKAT == SB_NR_UNDEF
 # include "unlinkat_pre_check.c"
 #endif
+
+#include "__pre_at_check.c"
diff --git a/libsandbox/wrapper-funcs/mkdirat_pre_check.c b/libsandbox/wrapper-funcs/mkdirat_pre_check.c
index 77a65df..0b48d1f 100644
--- a/libsandbox/wrapper-funcs/mkdirat_pre_check.c
+++ b/libsandbox/wrapper-funcs/mkdirat_pre_check.c
@@ -1,20 +1,13 @@
 bool sb_mkdirat_pre_check(const char *func, const char *pathname, int dirfd)
 {
 	char canonic[SB_PATH_MAX];
-	char dirfd_path[SB_PATH_MAX];
 
 	save_errno();
 
-	/* Expand the dirfd path first */
-	switch (resolve_dirfd_path(dirfd, pathname, dirfd_path, sizeof(dirfd_path))) {
-		case -1:
-			sb_debug_dyn("EARLY FAIL: %s(%s) @ resolve_dirfd_path: %s\n",
-				func, pathname, strerror(errno));
-			return false;
-		case 0:
-			pathname = dirfd_path;
-			break;
-	}
+	/* Check incoming args against common *at issues */
+	char dirfd_path[SB_PATH_MAX];
+	if (!sb_common_at_pre_check(func, &pathname, dirfd, dirfd_path, sizeof(dirfd_path)))
+		return false;
 
 	/* Then break down any relative/symlink paths */
 	if (-1 == canonicalize(pathname, canonic))
diff --git a/libsandbox/wrapper-funcs/openat_pre_check.c b/libsandbox/wrapper-funcs/openat_pre_check.c
index 0127708..5fd5eaa 100644
--- a/libsandbox/wrapper-funcs/openat_pre_check.c
+++ b/libsandbox/wrapper-funcs/openat_pre_check.c
@@ -15,17 +15,10 @@ bool sb_openat_pre_check(const char *func, const char *pathname, int dirfd, int
 
 	save_errno();
 
-	/* Expand the dirfd path first */
+	/* Check incoming args against common *at issues */
 	char dirfd_path[SB_PATH_MAX];
-	switch (resolve_dirfd_path(dirfd, pathname, dirfd_path, sizeof(dirfd_path))) {
-		case -1:
-			sb_debug_dyn("EARLY FAIL: %s(%s) @ resolve_dirfd_path: %s\n",
-				func, pathname, strerror(errno));
-			return false;
-		case 0:
-			pathname = dirfd_path;
-			break;
-	}
+	if (!sb_common_at_pre_check(func, &pathname, dirfd, dirfd_path, sizeof(dirfd_path)))
+		return false;
 
 	/* Doesn't exist -> skip permission checks */
 	struct stat st;
diff --git a/libsandbox/wrapper-funcs/unlinkat_pre_check.c b/libsandbox/wrapper-funcs/unlinkat_pre_check.c
index 9f5e7d7..c004d15 100644
--- a/libsandbox/wrapper-funcs/unlinkat_pre_check.c
+++ b/libsandbox/wrapper-funcs/unlinkat_pre_check.c
@@ -1,20 +1,13 @@
 bool sb_unlinkat_pre_check(const char *func, const char *pathname, int dirfd)
 {
 	char canonic[SB_PATH_MAX];
-	char dirfd_path[SB_PATH_MAX];
 
 	save_errno();
 
-	/* Expand the dirfd path first */
-	switch (resolve_dirfd_path(dirfd, pathname, dirfd_path, sizeof(dirfd_path))) {
-		case -1:
-			sb_debug_dyn("EARLY FAIL: %s(%s) @ resolve_dirfd_path: %s\n",
-				func, pathname, strerror(errno));
-			return false;
-		case 0:
-			pathname = dirfd_path;
-			break;
-	}
+	/* Check incoming args against common *at issues */
+	char dirfd_path[SB_PATH_MAX];
+	if (!sb_common_at_pre_check(func, &pathname, dirfd, dirfd_path, sizeof(dirfd_path)))
+		return false;
 
 	/* Then break down any relative/symlink paths */
 	if (-1 == canonicalize(pathname, canonic))
diff --git a/libsandbox/wrappers.h b/libsandbox/wrappers.h
index 5b97787..0aa58bb 100644
--- a/libsandbox/wrappers.h
+++ b/libsandbox/wrappers.h
@@ -28,5 +28,7 @@ attribute_hidden bool sb_mkdirat_pre_check  (const char *func, const char *pathn
 attribute_hidden bool sb_openat_pre_check   (const char *func, const char *pathname, int dirfd, int flags);
 attribute_hidden bool sb_openat64_pre_check (const char *func, const char *pathname, int dirfd, int flags);
 attribute_hidden bool sb_unlinkat_pre_check (const char *func, const char *pathname, int dirfd);
+attribute_hidden bool sb_common_at_pre_check(const char *func, const char **pathname, int dirfd,
+                                             char *dirfd_path, size_t dirfd_path_len);
 
 #endif
-- 
1.8.1.2

From 0b8a6d9773cc0e6d86bf1187f46817d5716698fe Mon Sep 17 00:00:00 2001
From: Mike Frysinger <vapier@gentoo.org>
Date: Mon, 24 Dec 2012 19:41:49 -0500
Subject: [PATCH 2/2] libsandbox: reject "" paths with *at funcs before
 checking the dirfd [missing file]

When it comes to processing errors, an empty path is checked before
an invalid dirfd.  Make sure sandbox matches that behavior for the
random testsuites out there that look for this.

Forgot to `git add` in the previous commit :/.

URL: https://bugs.gentoo.org/346929
Reported-by: Marien Zwart <marienz@gentoo.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
---
 libsandbox/wrapper-funcs/__pre_at_check.c | 34 +++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 libsandbox/wrapper-funcs/__pre_at_check.c

diff --git a/libsandbox/wrapper-funcs/__pre_at_check.c b/libsandbox/wrapper-funcs/__pre_at_check.c
new file mode 100644
index 0000000..f72c40c
--- /dev/null
+++ b/libsandbox/wrapper-funcs/__pre_at_check.c
@@ -0,0 +1,34 @@
+/*
+ * common *at() pre-checks.
+ *
+ * Copyright 1999-2012 Gentoo Foundation
+ * Licensed under the GPL-2
+ */
+
+/* We assume the parent has nested use with save/restore errno */
+bool sb_common_at_pre_check(const char *func, const char **pathname, int dirfd,
+                            char *dirfd_path, size_t dirfd_path_len)
+{
+	/* the empty path name should fail with ENOENT before any dirfd
+	 * checks get a chance to run #346929
+	 */
+	if (*pathname && *pathname[0] == '\0') {
+		errno = ENOENT;
+		sb_debug_dyn("EARLY FAIL: %s(%s): %s\n",
+			func, *pathname, strerror(errno));
+		return false;
+	}
+
+	/* Expand the dirfd path first */
+	switch (resolve_dirfd_path(dirfd, *pathname, dirfd_path, dirfd_path_len)) {
+		case -1:
+			sb_debug_dyn("EARLY FAIL: %s(%s) @ resolve_dirfd_path: %s\n",
+				func, *pathname, strerror(errno));
+			return false;
+		case 0:
+			*pathname = dirfd_path;
+			break;
+	}
+
+	return true;
+}
-- 
1.8.1.2