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v2.3.2
src/python/seccomp.pyx
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Paul Moore
python: add support for Python 3.x
28 фев 2017, 00:57
28 фев 2017, 00:57
8f31809
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# # Seccomp Library Python Bindings # # Copyright (c) 2012,2013,2017 Red Hat <pmoore@redhat.com> # Author: Paul Moore <paul@paul-moore.com> # # # This library is free software; you can redistribute it and/or modify it # under the terms of version 2.1 of the GNU Lesser General Public License as # published by the Free Software Foundation. # # This library is distributed in the hope that it will be useful, but WITHOUT # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or # FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License # for more details. # # You should have received a copy of the GNU Lesser General Public License # along with this library; if not, see <http://www.gnu.org/licenses>. # """ Python bindings for the libseccomp library The libseccomp library provides and easy to use, platform independent, interface to the Linux Kernel's syscall filtering mechanism: seccomp. The libseccomp API is designed to abstract away the underlying BPF based syscall filter language and present a more conventional function-call based filtering interface that should be familiar to, and easily adopted by application developers. Filter action values: KILL - kill the process ALLOW - allow the syscall to execute TRAP - a SIGSYS signal will be thrown ERRNO(x) - syscall will return (x) TRACE(x) - if the process is being traced, (x) will be returned to the tracing process via PTRACE_EVENT_SECCOMP and the PTRACE_GETEVENTMSG option Argument comparison values (see the Arg class): NE - arg != datum_a LT - arg < datum_a LE - arg <= datum_a EQ - arg == datum_a GT - arg > datum_a GE - arg >= datum_a MASKED_EQ - (arg & datum_b) == datum_a Example: import sys from seccomp import * # create a filter object with a default KILL action f = SyscallFilter(defaction=KILL) # add syscall filter rules to allow certain syscalls f.add_rule(ALLOW, "open") f.add_rule(ALLOW, "close") f.add_rule(ALLOW, "read", Arg(0, EQ, sys.stdin)) f.add_rule(ALLOW, "write", Arg(0, EQ, sys.stdout)) f.add_rule(ALLOW, "write", Arg(0, EQ, sys.stderr)) f.add_rule(ALLOW, "rt_sigreturn") # load the filter into the kernel f.load() """ __author__ = 'Paul Moore <paul@paul-moore.com>' __date__ = "3 February 2017" from cpython.version cimport PY_MAJOR_VERSION from libc.stdint cimport uint32_t import errno cimport libseccomp def c_str(string): """ Convert a Python string to a C string. Arguments: string - the Python string Description: Convert the Python string into a form usable by C taking into consideration the Python major version, e.g. Python 2.x or Python 3.x. See http://docs.cython.org/en/latest/src/tutorial/strings.html for more information. """ if PY_MAJOR_VERSION < 3: return string else: return bytes(string, "ascii") KILL = libseccomp.SCMP_ACT_KILL TRAP = libseccomp.SCMP_ACT_TRAP ALLOW = libseccomp.SCMP_ACT_ALLOW def ERRNO(int errno): """The action ERRNO(x) means that the syscall will return (x). To conform to Linux syscall calling conventions, the syscall return value should almost always be a negative number. """ return libseccomp.SCMP_ACT_ERRNO(errno) def TRACE(int value): """The action TRACE(x) means that, if the process is being traced, (x) will be returned to the tracing process via PTRACE_EVENT_SECCOMP and the PTRACE_GETEVENTMSG option. """ return libseccomp.SCMP_ACT_TRACE(value) NE = libseccomp.SCMP_CMP_NE LT = libseccomp.SCMP_CMP_LT LE = libseccomp.SCMP_CMP_LE EQ = libseccomp.SCMP_CMP_EQ GE = libseccomp.SCMP_CMP_GE GT = libseccomp.SCMP_CMP_GT MASKED_EQ = libseccomp.SCMP_CMP_MASKED_EQ def system_arch(): """ Return the system architecture value. Description: Returns the native system architecture value. """ return libseccomp.seccomp_arch_native() def resolve_syscall(arch, syscall): """ Resolve the syscall. Arguments: arch - the architecture value, e.g. Arch.* syscall - the syscall name or number Description: Resolve an architecture's syscall name to the correct number or the syscall number to the correct name. """ cdef char *ret_str if isinstance(syscall, basestring): return libseccomp.seccomp_syscall_resolve_name_rewrite(arch, c_str(syscall)) elif isinstance(syscall, int): ret_str = libseccomp.seccomp_syscall_resolve_num_arch(arch, syscall) if ret_str is NULL: raise ValueError('Unknown syscall %d on arch %d' % (syscall, arch)) else: return ret_str else: raise TypeError("Syscall must either be an int or str type") cdef class Arch: """ Python object representing the SyscallFilter architecture values. Data values: NATIVE - the native architecture X86 - 32-bit x86 X86_64 - 64-bit x86 X32 - 64-bit x86 using the x32 ABI ARM - ARM AARCH64 - 64-bit ARM MIPS - MIPS O32 ABI MIPS64 - MIPS 64-bit ABI MIPS64N32 - MIPS N32 ABI MIPSEL - MIPS little endian O32 ABI MIPSEL64 - MIPS little endian 64-bit ABI MIPSEL64N32 - MIPS little endian N32 ABI PPC64 - 64-bit PowerPC PPC - 32-bit PowerPC """ cdef int _token NATIVE = libseccomp.SCMP_ARCH_NATIVE X86 = libseccomp.SCMP_ARCH_X86 X86_64 = libseccomp.SCMP_ARCH_X86_64 X32 = libseccomp.SCMP_ARCH_X32 ARM = libseccomp.SCMP_ARCH_ARM AARCH64 = libseccomp.SCMP_ARCH_AARCH64 MIPS = libseccomp.SCMP_ARCH_MIPS MIPS64 = libseccomp.SCMP_ARCH_MIPS64 MIPS64N32 = libseccomp.SCMP_ARCH_MIPS64N32 MIPSEL = libseccomp.SCMP_ARCH_MIPSEL MIPSEL64 = libseccomp.SCMP_ARCH_MIPSEL64 MIPSEL64N32 = libseccomp.SCMP_ARCH_MIPSEL64N32 PPC = libseccomp.SCMP_ARCH_PPC PPC64 = libseccomp.SCMP_ARCH_PPC64 PPC64LE = libseccomp.SCMP_ARCH_PPC64LE S390 = libseccomp.SCMP_ARCH_S390 S390X = libseccomp.SCMP_ARCH_S390X def __cinit__(self, arch=libseccomp.SCMP_ARCH_NATIVE): """ Initialize the architecture object. Arguments: arch - the architecture name or token value Description: Create an architecture object using the given name or token value. """ if isinstance(arch, int): if arch == libseccomp.SCMP_ARCH_NATIVE: self._token = libseccomp.seccomp_arch_native() elif arch == libseccomp.SCMP_ARCH_X86: self._token = libseccomp.SCMP_ARCH_X86 elif arch == libseccomp.SCMP_ARCH_X86_64: self._token = libseccomp.SCMP_ARCH_X86_64 elif arch == libseccomp.SCMP_ARCH_X32: self._token = libseccomp.SCMP_ARCH_X32 elif arch == libseccomp.SCMP_ARCH_ARM: self._token = libseccomp.SCMP_ARCH_ARM elif arch == libseccomp.SCMP_ARCH_AARCH64: self._token = libseccomp.SCMP_ARCH_AARCH64 elif arch == libseccomp.SCMP_ARCH_MIPS: self._token = libseccomp.SCMP_ARCH_MIPS elif arch == libseccomp.SCMP_ARCH_MIPS64: self._token = libseccomp.SCMP_ARCH_MIPS64 elif arch == libseccomp.SCMP_ARCH_MIPS64N32: self._token = libseccomp.SCMP_ARCH_MIPS64N32 elif arch == libseccomp.SCMP_ARCH_MIPSEL: self._token = libseccomp.SCMP_ARCH_MIPSEL elif arch == libseccomp.SCMP_ARCH_MIPSEL64: self._token = libseccomp.SCMP_ARCH_MIPSEL64 elif arch == libseccomp.SCMP_ARCH_MIPSEL64N32: self._token = libseccomp.SCMP_ARCH_MIPSEL64N32 elif arch == libseccomp.SCMP_ARCH_PPC: self._token = libseccomp.SCMP_ARCH_PPC elif arch == libseccomp.SCMP_ARCH_PPC64: self._token = libseccomp.SCMP_ARCH_PPC64 elif arch == libseccomp.SCMP_ARCH_PPC64LE: self._token = libseccomp.SCMP_ARCH_PPC64LE elif arch == libseccomp.SCMP_ARCH_S390: self._token = libseccomp.SCMP_ARCH_S390 elif arch == libseccomp.SCMP_ARCH_S390X: self._token = libseccomp.SCMP_ARCH_S390X else: self._token = 0; elif isinstance(arch, basestring): self._token = libseccomp.seccomp_arch_resolve_name(c_str(arch)) else: raise TypeError("Architecture must be an int or str type") if self._token == 0: raise ValueError("Invalid architecture") def __int__(self): """ Convert the architecture object to a token value. Description: Convert the architecture object to an integer representing the architecture's token value. """ return self._token cdef class Attr: """ Python object representing the SyscallFilter attributes. Data values: ACT_DEFAULT - the filter's default action ACT_BADARCH - the filter's bad architecture action CTL_NNP - the filter's "no new privileges" flag CTL_NNP - the filter's thread sync flag """ ACT_DEFAULT = libseccomp.SCMP_FLTATR_ACT_DEFAULT ACT_BADARCH = libseccomp.SCMP_FLTATR_ACT_BADARCH CTL_NNP = libseccomp.SCMP_FLTATR_CTL_NNP CTL_TSYNC = libseccomp.SCMP_FLTATR_CTL_TSYNC API_TSKIP = libseccomp.SCMP_FLTATR_API_TSKIP cdef class Arg: """ Python object representing a SyscallFilter syscall argument. """ cdef libseccomp.scmp_arg_cmp _arg def __cinit__(self, arg, op, datum_a, datum_b = 0): """ Initialize the argument comparison. Arguments: arg - the argument number, starting at 0 op - the argument comparison operator, e.g. {NE,LT,LE,...} datum_a - argument value datum_b - argument value, only valid when op == MASKED_EQ Description: Create an argument comparison object for use with SyscallFilter. """ self._arg.arg = arg self._arg.op = op self._arg.datum_a = datum_a self._arg.datum_b = datum_b cdef libseccomp.scmp_arg_cmp to_c(self): """ Convert the object into a C structure. Description: Helper function which should only be used internally by SyscallFilter objects and exists for the sole purpose of making it easier to deal with the varadic functions of the libseccomp API, e.g. seccomp_rule_add(). """ return self._arg cdef class SyscallFilter: """ Python object representing a seccomp syscall filter. """ cdef int _defaction cdef libseccomp.scmp_filter_ctx _ctx def __cinit__(self, int defaction): self._ctx = libseccomp.seccomp_init(defaction) if self._ctx == NULL: raise RuntimeError("Library error") _defaction = defaction def __init__(self, defaction): """ Initialize the filter state Arguments: defaction - the default filter action Description: Initializes the seccomp filter state to the defaults. """ def __dealloc__(self): """ Destroys the filter state and releases any resources. Description: Destroys the seccomp filter state and releases any resources associated with the filter state. This function does not affect any seccomp filters already loaded into the kernel. """ if self._ctx != NULL: libseccomp.seccomp_release(self._ctx) def reset(self, int defaction = -1): """ Reset the filter state. Arguments: defaction - the default filter action Description: Resets the seccomp filter state to an initial default state, if a default filter action is not specified in the reset call the original action will be reused. This function does not affect any seccomp filters alread loaded into the kernel. """ if defaction == -1: defaction = self._defaction rc = libseccomp.seccomp_reset(self._ctx, defaction) if rc == -errno.EINVAL: raise ValueError("Invalid action") if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) _defaction = defaction def merge(self, SyscallFilter filter): """ Merge two existing SyscallFilter objects. Arguments: filter - a valid SyscallFilter object Description: Merges a valid SyscallFilter object with the current SyscallFilter object; the passed filter object will be reset on success. In order to successfully merge two seccomp filters they must have the same attribute values and not share any of the same architectures. """ rc = libseccomp.seccomp_merge(self._ctx, filter._ctx) if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) filter._ctx = NULL filter = SyscallFilter(filter._defaction) def exist_arch(self, arch): """ Check if the seccomp filter contains a given architecture. Arguments: arch - the architecture value, e.g. Arch.* Description: Test to see if a given architecture is included in the filter. Return True is the architecture exists, False if it does not exist. """ rc = libseccomp.seccomp_arch_exist(self._ctx, arch) if rc == 0: return True elif rc == -errno.EEXIST: return False elif rc == -errno.EINVAL: raise ValueError("Invalid architecture") else: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def add_arch(self, arch): """ Add an architecture to the filter. Arguments: arch - the architecture value, e.g. Arch.* Description: Add the given architecture to the filter. Any new rules added after this method returns successfully will be added to this new architecture, but any existing rules will not be added to the new architecture. """ rc = libseccomp.seccomp_arch_add(self._ctx, arch) if rc == -errno.EINVAL: raise ValueError("Invalid architecture") elif rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def remove_arch(self, arch): """ Remove an architecture from the filter. Arguments: arch - the architecture value, e.g. Arch.* Description: Remove the given architecture from the filter. The filter must always contain at least one architecture, so if only one architecture exists in the filter this method will fail. """ rc = libseccomp.seccomp_arch_remove(self._ctx, arch) if rc == -errno.EINVAL: raise ValueError("Invalid architecture") elif rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def load(self): """ Load the filter into the Linux Kernel. Description: Load the current filter into the Linux Kernel. As soon as the method returns the filter will be active and enforcing. """ rc = libseccomp.seccomp_load(self._ctx) if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def get_attr(self, attr): """ Get an attribute value from the filter. Arguments: attr - the attribute, e.g. Attr.* Description: Lookup the given attribute in the filter and return the attribute's value to the caller. """ cdef uint32_t value = 0 rc = libseccomp.seccomp_attr_get(self._ctx, attr, <uint32_t *>&value) if rc == -errno.EINVAL: raise ValueError("Invalid attribute") elif rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) return value def set_attr(self, attr, int value): """ Set a filter attribute. Arguments: attr - the attribute, e.g. Attr.* value - the attribute value Description: Lookup the given attribute in the filter and assign it the given value. """ rc = libseccomp.seccomp_attr_set(self._ctx, attr, value) if rc == -errno.EINVAL: raise ValueError("Invalid attribute") elif rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def syscall_priority(self, syscall, int priority): """ Set the filter priority of a syscall. Arguments: syscall - the syscall name or number priority - the priority of the syscall Description: Set the filter priority of the given syscall. A syscall with a higher priority will have less overhead in the generated filter code which is loaded into the system. Priority values can range from 0 to 255 inclusive. """ if priority < 0 or priority > 255: raise ValueError("Syscall priority must be between 0 and 255") if isinstance(syscall, str): syscall_str = syscall.encode() syscall_num = libseccomp.seccomp_syscall_resolve_name(syscall_str) elif isinstance(syscall, int): syscall_num = syscall else: raise TypeError("Syscall must either be an int or str type") rc = libseccomp.seccomp_syscall_priority(self._ctx, syscall_num, priority) if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def add_rule(self, int action, syscall, *args): """ Add a new rule to filter. Arguments: action - the rule action: KILL, TRAP, ERRNO(), TRACE(), or ALLOW syscall - the syscall name or number args - variable number of Arg objects Description: Add a new rule to the filter, matching on the given syscall and an optional list of argument comparisons. If the rule is triggered the given action will be taken by the kernel. In order for the rule to trigger, the syscall as well as each argument comparison must be true. In the case where the specific rule is not valid on a specific architecture, e.g. socket() on 32-bit x86, this method rewrites the rule to the best possible match. If you don't want this fule rewriting to take place use add_rule_exactly(). """ cdef libseccomp.scmp_arg_cmp c_arg[6] if isinstance(syscall, str): syscall_str = syscall.encode() syscall_num = libseccomp.seccomp_syscall_resolve_name(syscall_str) elif isinstance(syscall, int): syscall_num = syscall else: raise TypeError("Syscall must either be an int or str type") """ NOTE: the code below exists solely to deal with the varadic nature of seccomp_rule_add() function and the inability of Cython to handle this automatically """ if len(args) > 6: raise RuntimeError("Maximum number of arguments exceeded") cdef Arg arg for i, arg in enumerate(args): c_arg[i] = arg.to_c() if len(args) == 0: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, 0) elif len(args) == 1: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, len(args), c_arg[0]) elif len(args) == 2: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1]) elif len(args) == 3: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2]) elif len(args) == 4: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2], c_arg[3]) elif len(args) == 5: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2], c_arg[3], c_arg[4]) elif len(args) == 6: rc = libseccomp.seccomp_rule_add(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2], c_arg[3], c_arg[4], c_arg[5]) else: raise RuntimeError("Maximum number of arguments exceeded") if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def add_rule_exactly(self, int action, syscall, *args): """ Add a new rule to filter. Arguments: action - the rule action: KILL, TRAP, ERRNO(), TRACE(), or ALLOW syscall - the syscall name or number args - variable number of Arg objects Description: Add a new rule to the filter, matching on the given syscall and an optional list of argument comparisons. If the rule is triggered the given action will be taken by the kernel. In order for the rule to trigger, the syscall as well as each argument comparison must be true. This method attempts to add the filter rule exactly as specified which can cause problems on certain architectures, e.g. socket() on 32-bit x86. For a architecture independent version of this method use add_rule(). """ cdef libseccomp.scmp_arg_cmp c_arg[6] if isinstance(syscall, str): syscall_str = syscall.encode() syscall_num = libseccomp.seccomp_syscall_resolve_name(syscall_str) elif isinstance(syscall, int): syscall_num = syscall else: raise TypeError("Syscall must either be an int or str type") """ NOTE: the code below exists solely to deal with the varadic nature of seccomp_rule_add_exact() function and the inability of Cython to handle this automatically """ if len(args) > 6: raise RuntimeError("Maximum number of arguments exceeded") cdef Arg arg for i, arg in enumerate(args): c_arg[i] = arg.to_c() if len(args) == 0: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, 0) elif len(args) == 1: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, len(args), c_arg[0]) elif len(args) == 2: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1]) elif len(args) == 3: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2]) elif len(args) == 4: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2], c_arg[3]) elif len(args) == 5: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2], c_arg[3], c_arg[4]) elif len(args) == 6: rc = libseccomp.seccomp_rule_add_exact(self._ctx, action, syscall_num, len(args), c_arg[0], c_arg[1], c_arg[2], c_arg[3], c_arg[4], c_arg[5]) else: raise RuntimeError("Maximum number of arguments exceeded") if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def export_pfc(self, file): """ Export the filter in PFC format. Arguments: file - the output file Description: Output the filter in Pseudo Filter Code (PFC) to the given file. The output is functionally equivalent to the BPF based filter which is loaded into the Linux Kernel. """ rc = libseccomp.seccomp_export_pfc(self._ctx, file.fileno()) if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) def export_bpf(self, file): """ Export the filter in BPF format. Arguments: file - the output file Output the filter in Berkley Packet Filter (BPF) to the given file. The output is identical to what is loaded into the Linux Kernel. """ rc = libseccomp.seccomp_export_bpf(self._ctx, file.fileno()) if rc != 0: raise RuntimeError(str.format("Library error (errno = {0})", rc)) # kate: syntax python; # kate: indent-mode python; space-indent on; indent-width 4; mixedindent off;