posix.py

import logging

from .plugin import SimStatePlugin
from .filesystem import SimMount, Stat
from ..storage.file import SimFile, SimPacketsStream, Flags, SimFileDescriptor, SimFileDescriptorDuplex
from .. import sim_options as options

l = logging.getLogger(name=__name__)

max_fds = 8192


class PosixDevFS(SimMount):  # this'll be mounted at /dev
    def get(self, path):  # pylint: disable=arguments-differ
        if path == ["stdin"]:
            return self.state.posix.fd.get(0, None)
        elif path == ["stdout"]:
            return self.state.posix.fd.get(1, None)
        elif path == ["stderr"]:
            return self.state.posix.fd.get(2, None)
        else:
            return None

    def insert(self, path, simfile):  # pylint: disable=unused-argument, arguments-differ
        return False

    def delete(self, path):  # pylint: disable=unused-argument, arguments-differ
        return False

    def lookup(self, _):  # disable=unused-argument
        return False

    def merge(self, others, conditions, common_ancestor=None):  # pylint: disable=unused-argument, arguments-differ
        return False

    def widen(self, others):  # pylint: disable=unused-argument
        return False

    def copy(self, _):
        return self  # this holds no state!


class PosixProcFS(SimMount):
    """
    The virtual file system mounted at /proc (as of now, on Linux).
    """

    def get(self, path):  # pylint: disable=arguments-differ
        if path == [b"uptime"]:
            return SimFile(b"uptime", content=b"0 0")
        else:
            return None

    def insert(self, path, simfile):  # pylint: disable=unused-argument, arguments-differ
        return False

    def delete(self, path):  # pylint: disable=unused-argument, arguments-differ
        return False

    def lookup(self, _):  # disable=unused-argument
        return False

    def merge(self, others, conditions, common_ancestor=None):  # pylint: disable=unused-argument, arguments-differ
        return False

    def widen(self, others):  # pylint: disable=unused-argument
        return False

    def copy(self, _):
        return self  # this holds no state!


class SimSystemPosix(SimStatePlugin):
    """
    Data storage and interaction mechanisms for states with an environment conforming to posix.
    Available as ``state.posix``.
    """

    # __slots__ = [ 'maximum_symbolic_syscalls', 'files', 'max_length' ]

    # some posix constants
    SIG_BLOCK = 0
    SIG_UNBLOCK = 1
    SIG_SETMASK = 2

    EPERM = 1  # /* Operation not permitted */
    ENOENT = 2  # /* No such file or directory */
    ESRCH = 3  # /* No such process */
    EINTR = 4  # /* Interrupted system call */
    EIO = 5  # /* I/O error */
    ENXIO = 6  # /* No such device or address */
    E2BIG = 7  # /* Argument list too long */
    ENOEXEC = 8  # /* Exec format error */
    EBADF = 9  # /* Bad file number */
    ECHILD = 10  # /* No child processes */
    EAGAIN = 11  # /* Try again */
    ENOMEM = 12  # /* Out of memory */
    EACCES = 13  # /* Permission denied */
    EFAULT = 14  # /* Bad address */
    ENOTBLK = 15  # /* Block device required */
    EBUSY = 16  # /* Device or resource busy */
    EEXIST = 17  # /* File exists */
    EXDEV = 18  # /* Cross-device link */
    ENODEV = 19  # /* No such device */
    ENOTDIR = 20  # /* Not a directory */
    EISDIR = 21  # /* Is a directory */
    EINVAL = 22  # /* Invalid argument */
    ENFILE = 23  # /* File table overflow */
    EMFILE = 24  # /* Too many open files */
    ENOTTY = 25  # /* Not a typewriter */
    ETXTBSY = 26  # /* Text file busy */
    EFBIG = 27  # /* File too large */
    ENOSPC = 28  # /* No space left on device */
    ESPIPE = 29  # /* Illegal seek */
    EROFS = 30  # /* Read-only file system */
    EMLINK = 31  # /* Too many links */
    EPIPE = 32  # /* Broken pipe */
    EDOM = 33  # /* Math argument out of domain of func */
    ERANGE = 34  # /* Math result not representable */

    def __init__(
        self,
        stdin=None,
        stdout=None,
        stderr=None,
        fd=None,
        sockets=None,
        socket_queue=None,
        argv=None,
        argc=None,
        environ=None,
        auxv=None,
        tls_modules=None,
        sigmask=None,
        pid=None,
        ppid=None,
        uid=None,
        gid=None,
        brk=None,
    ):
        super().__init__()

        # some limits and constants
        self.sigmask_bits = 1024
        self.maximum_symbolic_syscalls = 255
        self.max_length = 2**16

        self.argc = argc
        self.argv = argv
        self.environ = environ
        self.auxv = auxv
        self.tls_modules = tls_modules if tls_modules is not None else {}
        self.brk = brk if brk is not None else 0x1B00000
        self._sigmask = sigmask
        self.pid = 1337 if pid is None else pid
        self.ppid = 1336 if ppid is None else ppid
        self.uid = 1000 if uid is None else uid
        self.gid = 1000 if gid is None else gid
        self.dev_fs = None
        self.proc_fs = None
        self.autotmp_counter = 0
        self._closed_fds = []

        self.sockets = sockets if sockets is not None else {}
        self.socket_queue = socket_queue if socket_queue is not None else []

        if stdin is None:
            stdin = SimPacketsStream("stdin", write_mode=False, writable=False, ident="stdin")
        if stdout is None:
            stdout = SimPacketsStream("stdout", write_mode=True, writable=True, ident="stdout")
        if stderr is None:
            stderr = SimPacketsStream("stderr", write_mode=True, writable=True, ident="stderr")

        if fd is None:
            fd = {}
            tty = SimFileDescriptorDuplex(stdin, stdout)

            # the initial fd layout just looks like this:
            # lrwx------ 1 audrey audrey 64 Jan 17 14:21 0 -> /dev/pts/4
            # lrwx------ 1 audrey audrey 64 Jan 17 14:21 1 -> /dev/pts/4
            # lrwx------ 1 audrey audrey 64 Jan 17 14:21 2 -> /dev/pts/4
            # but we want to distinguish the streams. we compromise by having 0 and 1 go to the "tty"
            # and stderr goes to a special stderr file
            fd[0] = tty
            fd[1] = tty
            fd[2] = SimFileDescriptor(stderr, 0)

        self.fd = fd
        # these are the storage mechanisms!
        self.stdin = stdin
        self.stdout = stdout
        self.stderr = stderr

    @SimStatePlugin.memo
    def copy(self, memo):
        o = super().copy(memo)

        o.sigmask_bits = self.sigmask_bits
        o.maximum_symbolic_syscalls = self.maximum_symbolic_syscalls
        o.max_length = self.max_length
        o.stdin = self.stdin.copy(memo)
        o.stdout = self.stdout.copy(memo)
        o.stderr = self.stderr.copy(memo)
        o.fd = {k: self.fd[k].copy(memo) for k in self.fd}
        o.sockets = {ident: tuple(x.copy(memo) for x in self.sockets[ident]) for ident in self.sockets}
        o.socket_queue = self.socket_queue  # shouldn't need to copy this - should be copied before use.
        o.argv = self.argv
        o.argc = self.argc
        o.environ = self.environ
        o.auxv = self.auxv
        o.tls_modules = self.tls_modules
        o._sigmask = self._sigmask
        o.pid = self.pid
        o.ppid = self.ppid
        o.uid = self.uid
        o.gid = self.gid
        o.brk = self.brk
        o.autotmp_counter = self.autotmp_counter
        o.dev_fs = self.dev_fs.copy(memo)
        o.proc_fs = self.proc_fs.copy(memo)
        o._closed_fds = list(self._closed_fds)

        return o

    @property
    def closed_fds(self):
        for _, f in self._closed_fds:
            f.set_state(self.state)
        return self._closed_fds

    def init_state(self):
        if self.dev_fs is None:
            self.dev_fs = PosixDevFS()
            self.state.fs.mount(b"/dev", self.dev_fs)
        if self.proc_fs is None:
            self.proc_fs = PosixProcFS()
            self.state.fs.mount(b"/proc", self.proc_fs)

    def set_brk(self, new_brk):
        # arch word size is not available at init for some reason, fix that here
        if isinstance(self.brk, int):
            self.brk = self.state.solver.BVV(self.brk, self.state.arch.bits)

        if new_brk.symbolic:
            l.warning("Program is requesting a symbolic brk! This cannot be emulated cleanly!")
            self.brk = self.state.solver.If(new_brk < self.brk, self.brk, new_brk)

        else:
            conc_start = self.state.solver.eval(self.brk)
            conc_end = self.state.solver.eval(new_brk)
            # failure case: new brk is less than old brk
            if conc_end < conc_start:
                pass
            else:
                # set break! we might not actually need to allocate memory though... pages
                self.brk = new_brk

                # if the old and new are in different pages, map
                # we check the byte before each of them since the "break" is the address of the first
                # "unmapped" byte...
                if ((conc_start - 1) ^ (conc_end - 1)) & ~0xFFF:
                    # align up
                    if conc_start & 0xFFF:
                        conc_start = (conc_start & ~0xFFF) + 0x1000
                    if conc_end & 0xFFF:
                        conc_end = (conc_end & ~0xFFF) + 0x1000
                    # TODO: figure out what permissions to use
                    try:
                        self.state.memory.map_region(conc_start, conc_end - conc_start, 7)
                    except SimMemoryError as e:
                        if len(e.args) >= 2 and type(e.args[1]) is int:
                            l.warning("The heap seems to have collided with another allocation. Be careful!")
                            self.brk = e.args[1]
                        else:
                            raise

        return self.brk

    def set_state(self, state):
        super().set_state(state)

        for fd in self.fd:
            self.fd[fd].set_state(state)

        self.stdin.set_state(state)
        self.stdout.set_state(state)
        self.stderr.set_state(state)

        if self.socket_queue:
            for sock_pair in self.socket_queue:
                if not sock_pair:
                    continue
                sock_pair[0].set_state(state)
                sock_pair[1].set_state(state)

        if self.sockets:
            for sock_pair in self.sockets.values():
                sock_pair[0].set_state(state)
                sock_pair[1].set_state(state)

    def _pick_fd(self):
        for fd in range(0, max_fds):
            if fd not in self.fd:
                return fd
        raise SimPosixError("exhausted file descriptors")

    def open(self, name, flags, preferred_fd=None):
        """
        Open a symbolic file. Basically open(2).

        :param name:            Path of the symbolic file, as a string or bytes.
        :type name:             string or bytes
        :param flags:           File operation flags, a bitfield of constants from open(2), as an AST
        :param preferred_fd:    Assign this fd if it's not already claimed.
        :return:                The file descriptor number allocated (maps through posix.get_fd to a SimFileDescriptor)
                                or -1 if the open fails.

        ``mode`` from open(2) is unsupported at present.
        """

        if len(name) == 0:
            return -1
        if type(name) is str:
            name = name.encode()

        # FIXME: HACK
        if self.uid != 0 and name.startswith(b"/var/run"):
            return -1

        # TODO: speed this up (editor's note: ...really? this is fine)
        if preferred_fd is not None and preferred_fd not in self.fd:
            fd = preferred_fd
        else:
            fd = self._pick_fd()

        flags = self.state.solver.eval(flags)
        create_file = (flags & Flags.O_ACCMODE) in (Flags.O_RDWR, Flags.O_WRONLY)

        simfile = self.state.fs.get(name)
        if simfile is None:
            ident = SimFile.make_ident(name)
            if not create_file:
                if options.ALL_FILES_EXIST not in self.state.options:
                    if options.ANY_FILE_MIGHT_EXIST in self.state.options:
                        file_exists = self.state.solver.BoolS("file_exists_%s" % ident, explicit_name=True)
                    else:
                        return -1
                else:
                    file_exists = True
                    l.warning(
                        "Trying to open unknown file %s - created a symbolic file since ALL_FILES_EXIST is set", name
                    )
                simfile = SimFile(
                    name,
                    ident=ident,
                    size=self.state.solver.BVS(
                        "filesize_%s" % ident, self.state.arch.bits, key=("file", ident, "filesize"), eternal=True
                    ),
                    file_exists=file_exists,
                )
            else:
                simfile = SimFile(name, ident=ident)
            if not self.state.fs.insert(name, simfile):
                return -1

        simfd = SimFileDescriptor(simfile, flags)
        simfd.set_state(self.state)
        self.fd[fd] = simfd
        if self.state.solver.is_true(simfd.file_exists):
            return fd
        else:
            m1 = self.state.solver.BVV(-1, self.state.arch.sizeof["int"])
            return self.state.solver.If(simfd.file_exists, fd, m1)

    def open_socket(self, ident):
        fd = self._pick_fd()

        # we need a sockpair, or a pair of storage mechanisms that will be duplexed to form the socket
        # we can get them from either:
        # a) the socket identifier store
        # b) the socket queue
        # c) making them ourselves
        # in the latter two cases we need to attach them to the socket identifier store

        # control flow sucks. we should be doing our analysis with nothing but mov instructions
        sockpair = None
        if ident not in self.sockets:
            if self.socket_queue:
                sockpair = self.socket_queue.pop(0)
                if sockpair is not None:
                    memo = {}
                    # Since we are not copying sockpairs when the FS state plugin branches, their original SimState
                    # instances might have long gone. Update their states before making copies.
                    sockpair[0].set_state(self.state)
                    sockpair[1].set_state(self.state)
                    sockpair = sockpair[0].copy(memo), sockpair[1].copy(memo)

            if sockpair is None:
                read_file = SimPacketsStream("socket %s read" % str(ident))
                write_file = SimPacketsStream("socket %s write" % str(ident))
                sockpair = (read_file, write_file)

            self.sockets[ident] = sockpair
        else:
            sockpair = self.sockets[ident]

        simfd = SimFileDescriptorDuplex(sockpair[0], sockpair[1])
        simfd.set_state(self.state)
        self.fd[fd] = simfd
        return fd

    def get_fd(self, fd, create_file=True):
        """
        Looks up the SimFileDescriptor associated with the given number (an AST).
        If the number is concrete and does not map to anything, return None.
        If the number is symbolic, constrain it to an open fd and create a new file for it.
        Set create_file to False if no write-access is planned (i.e. fd is read-only).
        """
        concr_fd = self._get_concrete_fd(fd, create_file)
        if concr_fd < 0 or max_fds <= concr_fd:
            return None
        return self.fd.get(concr_fd)

    def get_concrete_fd(self, fd, create_file=True):
        """
        Same behavior as get_fd(fd), only the result is a concrete integer fd (or -1) instead of a SimFileDescriptor.
        """
        concr_fd = self._get_concrete_fd(fd, create_file)
        if concr_fd < 0 or max_fds <= concr_fd:
            return -1
        return concr_fd

    def _get_concrete_fd(self, fd, create_file):
        if isinstance(fd, int):
            return fd
        if not self.state.satisfiable(extra_constraints=(fd < max_fds,)):
            return -1
        try:
            return self.state.solver.eval_one(fd, extra_constraints=(fd < max_fds,))
        except SimSolverError:
            pass

        new_filename = b"/tmp/angr_implicit_%d" % self.autotmp_counter
        self.autotmp_counter += 1
        if create_file:
            flags = Flags.O_RDWR
        else:
            flags = Flags.O_RDONLY
        concr_fd = self._pick_fd()
        if not self.state.satisfiable(extra_constraints=(concr_fd == fd,)):
            l.error("Could not look up a partially constrained symbolic fd")
            return -1
        opened_fd = self.open(new_filename, flags, preferred_fd=concr_fd)

        if not self.state.satisfiable(extra_constraints=(concr_fd == opened_fd,)):
            l.error("Something went wrong trying to open implicit temp")
            return -1
        self.state.add_constraints(fd == opened_fd)
        l.warning("Tried to look up a symbolic fd - constrained to %d and opened %s", concr_fd, new_filename)
        return concr_fd

    def close(self, fd):
        """
        Closes the given file descriptor (an AST).
        Returns whether the operation succeeded (a concrete boolean)
        """
        if not isinstance(fd, int):
            try:
                fd = self.state.solver.eval_one(fd, extra_constraints=(fd < max_fds,))
            except SimSolverError:
                l.error("Trying to close a symbolic file descriptor")
                return False

        if fd not in self.fd:
            l.info("Trying to close an unopened file descriptor")
            return False

        self.state.history.add_event("fs_close", fd=fd, close_idx=len(self.closed_fds))
        self.closed_fds.append((fd, self.fd[fd]))

        del self.fd[fd]
        return True

    def fstat(self, fd):
        stat, _ = self.fstat_with_result(fd)
        return stat

    def fstat_with_result(self, sim_fd):
        # sizes are AMD64-specific for symbolic files for now
        fd = None
        mount = None
        mode = None
        guest_path = None

        # set fd to the value of sim_fd, if positive and unique
        try:
            fd = self.state.solver.eval_one(sim_fd)
            if fd < 0 or max_fds <= fd:
                fd = None
        except SimSolverError:
            pass

        if fd is not None:
            fd_desc = self.state.posix.get_fd(fd)

            # a fd can be SimFileDescriptorDuplex which is not backed by a file
            if isinstance(fd_desc, SimFileDescriptor):
                sim_file = fd_desc.file
                mount = self.state.fs.get_mountpoint(sim_file.name)[0]  # TODO this is wrong. .name starts with file://
                if mount:
                    guest_path = mount.lookup(sim_file)
            result = 0
        else:
            if options.ALL_FILES_EXIST not in self.state.options:
                if options.ANY_FILE_MIGHT_EXIST in self.state.options:
                    m1 = self.state.solver.BVV(-1, self.state.arch.bits)
                    result = self.state.solver.If(self.state.solver.BoolS("file_exists"), 0, m1)
                else:
                    result = -1
            else:
                result = 0

        # if it is mounted, let the filesystem figure out the stat
        if guest_path is not None and mount is not None:
            stat = mount._get_stat(guest_path, dereference=True)
            if stat is None:
                raise SimPosixError(f"file {guest_path} does not exist on mount {mount}")
            size = stat.st_size
            mode = stat.st_mode
            ino = stat.st_ino
        else:
            # now we know it is not mounted, do the same as before
            if not fd:
                mode = self.state.solver.BVS("st_mode", 32, key=("api", "fstat", "st_mode"))
            else:
                mode = (
                    self.state.solver.BVS("st_mode", 32, key=("api", "fstat", "st_mode"))
                    if fd > 2
                    else self.state.solver.BVV(0, 32)
                )
            size = self.state.solver.BVS("st_size", 64, key=("api", "fstat", "st_size"))  # st_size
            ino = 0

        # return this weird bogus zero value to keep code paths in libc simple :\
        return (
            Stat(
                self.state.solver.BVV(0, 64),  # st_dev
                self.state.solver.BVV(ino, 64),  # st_ino
                self.state.solver.BVV(0, 64),  # st_nlink
                mode,  # st_mode
                self.state.solver.BVV(0, 32),  # st_uid (lol root)
                self.state.solver.BVV(0, 32),  # st_gid
                self.state.solver.BVV(0, 64),  # st_rdev
                size,  # st_size
                self.state.solver.BVV(0x400, 64),  # st_blksize
                self.state.solver.BVV(0, 64),  # st_blocks
                self.state.solver.BVV(0, 64),  # st_atime
                self.state.solver.BVV(0, 64),  # st_atimensec
                self.state.solver.BVV(0, 64),  # st_mtime
                self.state.solver.BVV(0, 64),  # st_mtimensec
                self.state.solver.BVV(0, 64),  # st_ctime
                self.state.solver.BVV(0, 64),  # st_ctimensec
            ),
            result,
        )

    def sigmask(self, sigsetsize=None):
        """
        Gets the current sigmask. If it's blank, a new one is created (of sigsetsize).

        :param sigsetsize: the size (in *bytes* of the sigmask set)
        :return: the sigmask
        """
        if self._sigmask is None:
            if sigsetsize is not None:
                sc = self.state.solver.eval(sigsetsize)
                self.state.add_constraints(sc == sigsetsize)
                self._sigmask = self.state.solver.BVS(
                    "initial_sigmask", sc * self.state.arch.byte_width, key=("initial_sigmask",), eternal=True
                )
            else:
                self._sigmask = self.state.solver.BVS(
                    "initial_sigmask", self.sigmask_bits, key=("initial_sigmask",), eternal=True
                )
        return self._sigmask

    def sigprocmask(self, how, new_mask, sigsetsize, valid_ptr=True):
        """
        Updates the signal mask.

        :param how: the "how" argument of sigprocmask (see manpage)
        :param new_mask: the mask modification to apply
        :param sigsetsize: the size (in *bytes* of the sigmask set)
        :param valid_ptr: is set if the new_mask was not NULL
        """
        oldmask = self.sigmask(sigsetsize)
        self._sigmask = self.state.solver.If(
            valid_ptr,
            self.state.solver.If(
                how == self.SIG_BLOCK,
                oldmask | new_mask,
                self.state.solver.If(
                    how == self.SIG_UNBLOCK,
                    oldmask & (~new_mask),
                    self.state.solver.If(how == self.SIG_SETMASK, new_mask, oldmask),
                ),
            ),
            oldmask,
        )

    def merge(self, others, merge_conditions, common_ancestor=None):
        for o in others:
            if len(self.fd) != len(o.fd):
                raise SimMergeError("Can't merge states with disparate open file descriptors")
            for fd in self.fd:
                if fd not in o.fd:
                    raise SimMergeError("Can't merge states with disparate open file descriptors")
            if len(self.sockets) != len(o.sockets):
                raise SimMergeError("Can't merge states with disparate sockets")
            for ident in self.sockets:
                if ident not in o.sockets:
                    raise SimMergeError("Can't merge states with disparate sockets")
            if len(self.socket_queue) != len(o.socket_queue) or any(
                x is not y for x, y in zip(self.socket_queue, o.socket_queue)
            ):
                raise SimMergeError("Can't merge states with disparate socket queues")

        merging_occurred = False
        for fd in self.fd:
            try:
                common_fd = common_ancestor.fd[fd]
            except (AttributeError, KeyError):
                common_fd = None
            merging_occurred |= self.fd[fd].merge(
                [o.fd[fd] for o in others], merge_conditions, common_ancestor=common_fd
            )
        for ident in self.sockets:
            try:
                common_sock = common_ancestor.sockets[ident]
            except (AttributeError, KeyError):
                common_sock = None
            merging_occurred |= self.sockets[ident][0].merge(
                [o.sockets[ident][0] for o in others], merge_conditions, common_ancestor=common_sock[0]
            )
            merging_occurred |= self.sockets[ident][1].merge(
                [o.sockets[ident][1] for o in others], merge_conditions, common_ancestor=common_sock[1]
            )

        # pylint: disable=no-member
        # pylint seems to be seriously flipping out here for reasons I'm unsure of
        # it thinks others is a list of bools somehow
        merging_occurred |= self.stdin.merge(
            [o.stdin for o in others],
            merge_conditions,
            common_ancestor=common_ancestor.stdin if common_ancestor is not None else None,
        )
        merging_occurred |= self.stdout.merge(
            [o.stdout for o in others],
            merge_conditions,
            common_ancestor=common_ancestor.stdout if common_ancestor is not None else None,
        )
        merging_occurred |= self.stderr.merge(
            [o.stderr for o in others],
            merge_conditions,
            common_ancestor=common_ancestor.stderr if common_ancestor is not None else None,
        )

        return merging_occurred

    def widen(self, _):
        raise SimMergeError("Widening the system state is unsupported")

    def dump_file_by_path(self, path, **kwargs):
        """
        Returns the concrete content for a file by path.

        :param path: file path as string
        :param kwargs: passed to state.solver.eval
        :return: file contents as string
        """
        file = self.state.fs.get(path)
        if file is None:
            return None
        return file.concretize(**kwargs)

    def dumps(self, fd, **kwargs):
        """
        Returns the concrete content for a file descriptor.

        BACKWARD COMPATIBILITY: if you ask for file descriptors 0 1 or 2, it will return the data from stdin, stdout,
        or stderr as a flat string.

        :param fd:  A file descriptor.
        :return:    The concrete content.
        :rtype:     str
        """
        if 0 <= fd <= 2:
            data = [self.stdin, self.stdout, self.stderr][fd].concretize(**kwargs)
            if type(data) is list:
                data = b"".join(data)
            return data
        return self.get_fd(fd).concretize(**kwargs)


from angr.sim_state import SimState

SimState.register_default("posix", SimSystemPosix)

from ..errors import SimPosixError, SimSolverError, SimMergeError, SimMemoryError