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freebsd/contrib/capsicum-test/openat.cc
Enji Cooper 8ac5aef8f3 Integrate capsicum-test into the FreeBSD test suite 
This change takes capsicum-test from upstream and applies some local changes to make the
tests work on FreeBSD when executed via Kyua.

The local modifications are as follows:
1. Make `OpenatTest.WithFlag` pass with the new dot-dot lookup behavior in FreeBSD 12.x+.
2. capsicum-test references a set of helper binaries: `mini-me`, `mini-me.noexec`, and
   `mini-me.setuid`, as part of the execve/fexecve tests, via execve, fexecve, and open.
   It achieves this upstream by assuming `mini-me*` is in the current directory, however,
   in order for Kyua to execute `capsicum-test`, it needs to provide a full path to
   `mini-me*`. In order to achieve this, I made `capsicum-test` cache the executable's
   path from argv[0] in main(..) and use the cached value to compute the path to
   `mini-me*` as part of the execve/fexecve testcases.
3. The capsicum-test test suite assumes that it's always being run on CAPABILITIES enabled
   kernels. However, there's a chance that the test will be run on a host without a
   CAPABILITIES enabled kernel, so we must check for the support before running the tests.
   The way to achieve this is to add the relevant `feature_present("security_capabilities")`
   check to SetupEnvironment::SetUp() and skip the tests when the support is not available.
   While here, add a check for `kern.trap_enotcap` being enabled. As noted by markj@ in
   https://github.com/google/capsicum-test/issues/23, this sysctl being enabled can trigger
   non-deterministic failures. Therefore, the tests should be skipped if this sysctl is
   enabled.

All local changes have been submitted to the capsicum-test project
(https://github.com/google/capsicum-test) and are in various stages of review.
Please see the following pull requests for more details:
1. https://github.com/google/capsicum-test/pull/35
2. https://github.com/google/capsicum-test/pull/41
3. https://github.com/google/capsicum-test/pull/42

Reviewed by:	asomers
Discussed with:	emaste, markj
Approved by:	emaste (mentor)
MFC after:	2 months
Differential Revision: https://reviews.freebsd.org/D19758
2019-04-01 21:24:50 +00:00

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