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https://git.hardenedbsd.org/hardenedbsd/HardenedBSD.git
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8cf5812af4
Update the tests to check O_RESOLVE_BENEATH instead. If this looks reasonable, I'll try to upstream this change. This keeps a compat fallback for O_BENEATH since the Linux port still has/had O_BENEATH with "no .., no absolute paths" semantics. Test Plan: `/usr/tests/sys/capsicum/capsicum-test -u 977` passes and runs the O_RESOLVE_BENEATH tests. Reviewed By: markj Differential Revision: https://reviews.freebsd.org/D29016
367 lines
15 KiB
C++
367 lines
15 KiB
C++
#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <sys/ioctl.h>
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#include <string>
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#include "capsicum.h"
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#include "capsicum-test.h"
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#include "syscalls.h"
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// Check an open call works and close the resulting fd.
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#define EXPECT_OPEN_OK(f) do { \
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SCOPED_TRACE(#f); \
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int _fd = f; \
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EXPECT_OK(_fd); \
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close(_fd); \
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} while (0)
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static void CreateFile(const char *filename, const char *contents) {
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int fd = open(filename, O_CREAT|O_RDWR, 0644);
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EXPECT_OK(fd);
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EXPECT_OK(write(fd, contents, strlen(contents)));
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close(fd);
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}
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// Test openat(2) in a variety of sitations to ensure that it obeys Capsicum
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// "strict relative" rules:
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//
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// 1. Use strict relative lookups in capability mode or when operating
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// relative to a capability.
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// 2. When performing strict relative lookups, absolute paths (including
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// symlinks to absolute paths) are not allowed, nor are paths containing
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// '..' components.
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//
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// These rules apply when:
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// - the directory FD is a Capsicum capability
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// - the process is in capability mode
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// - the openat(2) operation includes the O_BENEATH flag.
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FORK_TEST(Openat, Relative) {
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int etc = open("/etc/", O_RDONLY);
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EXPECT_OK(etc);
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cap_rights_t r_base;
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cap_rights_init(&r_base, CAP_READ, CAP_WRITE, CAP_SEEK, CAP_LOOKUP, CAP_FCNTL, CAP_IOCTL);
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cap_rights_t r_ro;
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cap_rights_init(&r_ro, CAP_READ);
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cap_rights_t r_rl;
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cap_rights_init(&r_rl, CAP_READ, CAP_LOOKUP);
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int etc_cap = dup(etc);
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EXPECT_OK(etc_cap);
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EXPECT_OK(cap_rights_limit(etc_cap, &r_ro));
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int etc_cap_ro = dup(etc);
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EXPECT_OK(etc_cap_ro);
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EXPECT_OK(cap_rights_limit(etc_cap_ro, &r_rl));
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int etc_cap_base = dup(etc);
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EXPECT_OK(etc_cap_base);
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EXPECT_OK(cap_rights_limit(etc_cap_base, &r_base));
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#ifdef HAVE_CAP_FCNTLS_LIMIT
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// Also limit fcntl(2) subrights.
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EXPECT_OK(cap_fcntls_limit(etc_cap_base, CAP_FCNTL_GETFL));
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#endif
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#ifdef HAVE_CAP_IOCTLS_LIMIT
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// Also limit ioctl(2) subrights.
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cap_ioctl_t ioctl_nread = FIONREAD;
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EXPECT_OK(cap_ioctls_limit(etc_cap_base, &ioctl_nread, 1));
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#endif
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// openat(2) with regular file descriptors in non-capability mode
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// Should Just Work (tm).
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EXPECT_OPEN_OK(openat(etc, "/etc/passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(AT_FDCWD, "/etc/passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(etc, "passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(etc, "../etc/passwd", O_RDONLY));
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// Lookups relative to capabilities should be strictly relative.
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// When not in capability mode, we don't actually require CAP_LOOKUP.
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EXPECT_OPEN_OK(openat(etc_cap_ro, "passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(etc_cap_base, "passwd", O_RDONLY));
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// Performing openat(2) on a path with leading slash ignores
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// the provided directory FD.
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EXPECT_OPEN_OK(openat(etc_cap_ro, "/etc/passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(etc_cap_base, "/etc/passwd", O_RDONLY));
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// Relative lookups that go upward are not allowed.
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc_cap_ro, "../etc/passwd", O_RDONLY);
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc_cap_base, "../etc/passwd", O_RDONLY);
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// A file opened relative to a capability should itself be a capability.
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int fd = openat(etc_cap_base, "passwd", O_RDONLY);
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EXPECT_OK(fd);
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cap_rights_t rights;
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EXPECT_OK(cap_rights_get(fd, &rights));
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EXPECT_RIGHTS_IN(&rights, &r_base);
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#ifdef HAVE_CAP_FCNTLS_LIMIT
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cap_fcntl_t fcntls;
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EXPECT_OK(cap_fcntls_get(fd, &fcntls));
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EXPECT_EQ((cap_fcntl_t)CAP_FCNTL_GETFL, fcntls);
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#endif
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#ifdef HAVE_CAP_IOCTLS_LIMIT
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cap_ioctl_t ioctls[16];
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ssize_t nioctls;
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memset(ioctls, 0, sizeof(ioctls));
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nioctls = cap_ioctls_get(fd, ioctls, 16);
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EXPECT_OK(nioctls);
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EXPECT_EQ(1, nioctls);
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EXPECT_EQ((cap_ioctl_t)FIONREAD, ioctls[0]);
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#endif
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close(fd);
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// Enter capability mode; now ALL lookups are strictly relative.
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EXPECT_OK(cap_enter());
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// Relative lookups on regular files or capabilities with CAP_LOOKUP
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// ought to succeed.
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EXPECT_OPEN_OK(openat(etc, "passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(etc_cap_ro, "passwd", O_RDONLY));
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EXPECT_OPEN_OK(openat(etc_cap_base, "passwd", O_RDONLY));
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// Lookup relative to capabilities without CAP_LOOKUP should fail.
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EXPECT_NOTCAPABLE(openat(etc_cap, "passwd", O_RDONLY));
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// Absolute lookups should fail.
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EXPECT_CAPMODE(openat(AT_FDCWD, "/etc/passwd", O_RDONLY));
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc, "/etc/passwd", O_RDONLY);
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc_cap_ro, "/etc/passwd", O_RDONLY);
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// Lookups containing '..' should fail in capability mode.
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc, "../etc/passwd", O_RDONLY);
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc_cap_ro, "../etc/passwd", O_RDONLY);
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EXPECT_OPENAT_FAIL_TRAVERSAL(etc_cap_base, "../etc/passwd", O_RDONLY);
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fd = openat(etc, "passwd", O_RDONLY);
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EXPECT_OK(fd);
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// A file opened relative to a capability should itself be a capability.
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fd = openat(etc_cap_base, "passwd", O_RDONLY);
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EXPECT_OK(fd);
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EXPECT_OK(cap_rights_get(fd, &rights));
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EXPECT_RIGHTS_IN(&rights, &r_base);
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close(fd);
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fd = openat(etc_cap_ro, "passwd", O_RDONLY);
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EXPECT_OK(fd);
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EXPECT_OK(cap_rights_get(fd, &rights));
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EXPECT_RIGHTS_IN(&rights, &r_rl);
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close(fd);
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}
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#define TOPDIR "cap_topdir"
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#define SUBDIR TOPDIR "/subdir"
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class OpenatTest : public ::testing::Test {
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public:
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// Build a collection of files, subdirs and symlinks:
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// /tmp/cap_topdir/
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// /topfile
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// /subdir/
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// /subdir/bottomfile
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// /symlink.samedir -> topfile
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// /dsymlink.samedir -> ./
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// /symlink.down -> subdir/bottomfile
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// /dsymlink.down -> subdir/
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// /symlink.absolute_out -> /etc/passwd
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// /dsymlink.absolute_out -> /etc/
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// /symlink.relative_in -> ../../tmp/cap_topdir/topfile
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// /dsymlink.relative_in -> ../../tmp/cap_topdir/
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// /symlink.relative_out -> ../../etc/passwd
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// /dsymlink.relative_out -> ../../etc/
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// /subdir/dsymlink.absolute_in -> /tmp/cap_topdir/
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// /subdir/dsymlink.up -> ../
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// /subdir/symlink.absolute_in -> /tmp/cap_topdir/topfile
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// /subdir/symlink.up -> ../topfile
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// (In practice, this is a little more complicated because tmpdir might
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// not be "/tmp".)
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OpenatTest() {
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// Create a couple of nested directories
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int rc = mkdir(TmpFile(TOPDIR), 0755);
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EXPECT_OK(rc);
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if (rc < 0) {
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EXPECT_EQ(EEXIST, errno);
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}
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rc = mkdir(TmpFile(SUBDIR), 0755);
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EXPECT_OK(rc);
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if (rc < 0) {
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EXPECT_EQ(EEXIST, errno);
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}
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// Figure out a path prefix (like "../..") that gets us to the root
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// directory from TmpFile(TOPDIR).
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const char *p = TmpFile(TOPDIR); // maybe "/tmp/somewhere/cap_topdir"
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std::string dots2root = "..";
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while (*p++ != '\0') {
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if (*p == '/') {
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dots2root += "/..";
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}
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}
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// Create normal files in each.
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CreateFile(TmpFile(TOPDIR "/topfile"), "Top-level file");
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CreateFile(TmpFile(SUBDIR "/bottomfile"), "File in subdirectory");
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// Create various symlinks to files.
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EXPECT_OK(symlink("topfile", TmpFile(TOPDIR "/symlink.samedir")));
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EXPECT_OK(symlink("subdir/bottomfile", TmpFile(TOPDIR "/symlink.down")));
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EXPECT_OK(symlink(TmpFile(TOPDIR "/topfile"), TmpFile(SUBDIR "/symlink.absolute_in")));
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EXPECT_OK(symlink("/etc/passwd", TmpFile(TOPDIR "/symlink.absolute_out")));
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std::string dots2top = dots2root + TmpFile(TOPDIR "/topfile");
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EXPECT_OK(symlink(dots2top.c_str(), TmpFile(TOPDIR "/symlink.relative_in")));
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std::string dots2passwd = dots2root + "/etc/passwd";
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EXPECT_OK(symlink(dots2passwd.c_str(), TmpFile(TOPDIR "/symlink.relative_out")));
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EXPECT_OK(symlink("../topfile", TmpFile(SUBDIR "/symlink.up")));
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// Create various symlinks to directories.
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EXPECT_OK(symlink("./", TmpFile(TOPDIR "/dsymlink.samedir")));
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EXPECT_OK(symlink("subdir/", TmpFile(TOPDIR "/dsymlink.down")));
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EXPECT_OK(symlink(TmpFile(TOPDIR "/"), TmpFile(SUBDIR "/dsymlink.absolute_in")));
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EXPECT_OK(symlink("/etc/", TmpFile(TOPDIR "/dsymlink.absolute_out")));
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std::string dots2cwd = dots2root + tmpdir + "/";
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EXPECT_OK(symlink(dots2cwd.c_str(), TmpFile(TOPDIR "/dsymlink.relative_in")));
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std::string dots2etc = dots2root + "/etc/";
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EXPECT_OK(symlink(dots2etc.c_str(), TmpFile(TOPDIR "/dsymlink.relative_out")));
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EXPECT_OK(symlink("../", TmpFile(SUBDIR "/dsymlink.up")));
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// Open directory FDs for those directories and for cwd.
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dir_fd_ = open(TmpFile(TOPDIR), O_RDONLY);
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EXPECT_OK(dir_fd_);
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sub_fd_ = open(TmpFile(SUBDIR), O_RDONLY);
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EXPECT_OK(sub_fd_);
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cwd_ = openat(AT_FDCWD, ".", O_RDONLY);
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EXPECT_OK(cwd_);
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// Move into the directory for the test.
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EXPECT_OK(fchdir(dir_fd_));
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}
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~OpenatTest() {
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fchdir(cwd_);
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close(cwd_);
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close(sub_fd_);
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close(dir_fd_);
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unlink(TmpFile(SUBDIR "/symlink.up"));
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unlink(TmpFile(SUBDIR "/symlink.absolute_in"));
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unlink(TmpFile(TOPDIR "/symlink.absolute_out"));
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unlink(TmpFile(TOPDIR "/symlink.relative_in"));
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unlink(TmpFile(TOPDIR "/symlink.relative_out"));
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unlink(TmpFile(TOPDIR "/symlink.down"));
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unlink(TmpFile(TOPDIR "/symlink.samedir"));
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unlink(TmpFile(SUBDIR "/dsymlink.up"));
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unlink(TmpFile(SUBDIR "/dsymlink.absolute_in"));
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unlink(TmpFile(TOPDIR "/dsymlink.absolute_out"));
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unlink(TmpFile(TOPDIR "/dsymlink.relative_in"));
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unlink(TmpFile(TOPDIR "/dsymlink.relative_out"));
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unlink(TmpFile(TOPDIR "/dsymlink.down"));
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unlink(TmpFile(TOPDIR "/dsymlink.samedir"));
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unlink(TmpFile(SUBDIR "/bottomfile"));
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unlink(TmpFile(TOPDIR "/topfile"));
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rmdir(TmpFile(SUBDIR));
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rmdir(TmpFile(TOPDIR));
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}
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// Check openat(2) policing that is common across capabilities, capability mode and O_BENEATH.
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void CheckPolicing(int oflag) {
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// OK for normal access.
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EXPECT_OPEN_OK(openat(dir_fd_, "topfile", O_RDONLY|oflag));
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EXPECT_OPEN_OK(openat(dir_fd_, "subdir/bottomfile", O_RDONLY|oflag));
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EXPECT_OPEN_OK(openat(sub_fd_, "bottomfile", O_RDONLY|oflag));
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EXPECT_OPEN_OK(openat(sub_fd_, ".", O_RDONLY|oflag));
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// Can't open paths with ".." in them.
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "../topfile", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "../subdir/bottomfile", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "..", O_RDONLY|oflag);
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#ifdef HAVE_OPENAT_INTERMEDIATE_DOTDOT
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// OK for dotdot lookups that don't escape the top directory
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EXPECT_OPEN_OK(openat(dir_fd_, "subdir/../topfile", O_RDONLY|oflag));
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#endif
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// Check that we can't escape the top directory by the cunning
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// ruse of going via a subdirectory.
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "subdir/../../etc/passwd", O_RDONLY|oflag);
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// Should only be able to open symlinks that stay within the directory.
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.samedir", O_RDONLY|oflag));
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.down", O_RDONLY|oflag));
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "symlink.absolute_out", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "symlink.relative_in", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "symlink.relative_out", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "symlink.absolute_in", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "symlink.up", O_RDONLY|oflag);
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EXPECT_OPEN_OK(openat(dir_fd_, "dsymlink.samedir/topfile", O_RDONLY|oflag));
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EXPECT_OPEN_OK(openat(dir_fd_, "dsymlink.down/bottomfile", O_RDONLY|oflag));
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "dsymlink.absolute_out/passwd", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "dsymlink.relative_in/topfile", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "dsymlink.relative_out/passwd", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "dsymlink.absolute_in/topfile", O_RDONLY|oflag);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "dsymlink.up/topfile", O_RDONLY|oflag);
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// Although recall that O_NOFOLLOW prevents symlink following in final component.
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EXPECT_SYSCALL_FAIL(E_TOO_MANY_LINKS, openat(dir_fd_, "symlink.samedir", O_RDONLY|O_NOFOLLOW|oflag));
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EXPECT_SYSCALL_FAIL(E_TOO_MANY_LINKS, openat(dir_fd_, "symlink.down", O_RDONLY|O_NOFOLLOW|oflag));
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}
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protected:
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int dir_fd_;
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int sub_fd_;
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int cwd_;
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};
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TEST_F(OpenatTest, WithCapability) {
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// Any kind of symlink can be opened relative to an ordinary directory FD.
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.samedir", O_RDONLY));
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.down", O_RDONLY));
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.absolute_out", O_RDONLY));
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.relative_in", O_RDONLY));
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EXPECT_OPEN_OK(openat(dir_fd_, "symlink.relative_out", O_RDONLY));
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EXPECT_OPEN_OK(openat(sub_fd_, "symlink.absolute_in", O_RDONLY));
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EXPECT_OPEN_OK(openat(sub_fd_, "symlink.up", O_RDONLY));
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// Now make both DFDs into Capsicum capabilities.
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cap_rights_t r_rl;
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cap_rights_init(&r_rl, CAP_READ, CAP_LOOKUP, CAP_FCHDIR);
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EXPECT_OK(cap_rights_limit(dir_fd_, &r_rl));
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EXPECT_OK(cap_rights_limit(sub_fd_, &r_rl));
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CheckPolicing(0);
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// Use of AT_FDCWD is independent of use of a capability.
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// Can open paths starting with "/" against a capability dfd, because the dfd is ignored.
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}
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FORK_TEST_F(OpenatTest, InCapabilityMode) {
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EXPECT_OK(cap_enter()); // Enter capability mode
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CheckPolicing(0);
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// Use of AT_FDCWD is banned in capability mode.
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EXPECT_CAPMODE(openat(AT_FDCWD, "topfile", O_RDONLY));
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EXPECT_CAPMODE(openat(AT_FDCWD, "subdir/bottomfile", O_RDONLY));
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EXPECT_CAPMODE(openat(AT_FDCWD, "/etc/passwd", O_RDONLY));
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// Can't open paths starting with "/" in capability mode.
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "/etc/passwd", O_RDONLY);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "/etc/passwd", O_RDONLY);
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}
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#if !defined(O_RESOLVE_BENEATH) && defined(O_BENEATH)
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#define O_RESOLVE_BENEATH O_BENEATH
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#endif
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#ifdef O_RESOLVE_BENEATH
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TEST_F(OpenatTest, WithFlag) {
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CheckPolicing(O_RESOLVE_BENEATH);
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// Check with AT_FDCWD.
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EXPECT_OPEN_OK(openat(AT_FDCWD, "topfile", O_RDONLY|O_RESOLVE_BENEATH));
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EXPECT_OPEN_OK(openat(AT_FDCWD, "subdir/bottomfile", O_RDONLY|O_RESOLVE_BENEATH));
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// Can't open paths starting with "/" with O_RESOLVE_BENEATH specified.
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EXPECT_OPENAT_FAIL_TRAVERSAL(AT_FDCWD, "/etc/passwd", O_RDONLY|O_RESOLVE_BENEATH);
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EXPECT_OPENAT_FAIL_TRAVERSAL(dir_fd_, "/etc/passwd", O_RDONLY|O_RESOLVE_BENEATH);
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EXPECT_OPENAT_FAIL_TRAVERSAL(sub_fd_, "/etc/passwd", O_RDONLY|O_RESOLVE_BENEATH);
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}
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FORK_TEST_F(OpenatTest, WithFlagInCapabilityMode) {
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EXPECT_OK(cap_enter()); // Enter capability mode
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CheckPolicing(O_RESOLVE_BENEATH);
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}
|
|
#endif
|