f374ba41f5
Release notes are available at https://www.openssh.com/txt/release-9.2 OpenSSH 9.2 contains fixes for two security problems and a memory safety problem. The memory safety problem is not believed to be exploitable. These fixes have already been committed to OpenSSH 9.1 in FreeBSD. Some other notable items from the release notes: * ssh(1): add a new EnableEscapeCommandline ssh_config(5) option that controls whether the client-side ~C escape sequence that provides a command-line is available. Among other things, the ~C command-line could be used to add additional port-forwards at runtime. * sshd(8): add support for channel inactivity timeouts via a new sshd_config(5) ChannelTimeout directive. This allows channels that have not seen traffic in a configurable interval to be automatically closed. Different timeouts may be applied to session, X11, agent and TCP forwarding channels. * sshd(8): add a sshd_config UnusedConnectionTimeout option to terminate client connections that have no open channels for a length of time. This complements the ChannelTimeout option above. * sshd(8): add a -V (version) option to sshd like the ssh client has. * scp(1), sftp(1): add a -X option to both scp(1) and sftp(1) to allow control over some SFTP protocol parameters: the copy buffer length and the number of in-flight requests, both of which are used during upload/download. Previously these could be controlled in sftp(1) only. This makes them available in both SFTP protocol clients using the same option character sequence. * ssh-keyscan(1): allow scanning of complete CIDR address ranges, e.g. "ssh-keyscan 192.168.0.0/24". If a CIDR range is passed, then it will be expanded to all possible addresses in the range including the all-0s and all-1s addresses. bz#976 * ssh(1): support dynamic remote port forwarding in escape command-line's -R processing. bz#3499 MFC after: 1 week Sponsored by: The FreeBSD Foundation
461 lines
12 KiB
C
461 lines
12 KiB
C
/*
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* Copyright (c) 2012 Will Drewry <wad@dataspill.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* Uncomment the SANDBOX_SECCOMP_FILTER_DEBUG macro below to help diagnose
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* filter breakage during development. *Do not* use this in production,
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* as it relies on making library calls that are unsafe in signal context.
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*
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* Instead, live systems the auditctl(8) may be used to monitor failures.
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* E.g.
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* auditctl -a task,always -F uid=<privsep uid>
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*/
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/* #define SANDBOX_SECCOMP_FILTER_DEBUG 1 */
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#if 0
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/*
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* For older toolchains, it may be necessary to use the kernel
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* headers directly.
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*/
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#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
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# include <asm/siginfo.h>
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# define __have_siginfo_t 1
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# define __have_sigval_t 1
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# define __have_sigevent_t 1
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#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
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#endif
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#include "includes.h"
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#ifdef SANDBOX_SECCOMP_FILTER
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#include <sys/types.h>
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#include <sys/resource.h>
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#include <sys/prctl.h>
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#include <sys/mman.h>
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#include <sys/syscall.h>
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#include <linux/net.h>
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#include <linux/audit.h>
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#include <linux/filter.h>
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#include <linux/seccomp.h>
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#include <elf.h>
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#include <asm/unistd.h>
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#ifdef __s390__
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#include <asm/zcrypt.h>
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#endif
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#include <errno.h>
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#include <signal.h>
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#include <stdarg.h>
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#include <stddef.h> /* for offsetof */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "log.h"
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#include "ssh-sandbox.h"
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#include "xmalloc.h"
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/* Linux seccomp_filter sandbox */
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#define SECCOMP_FILTER_FAIL SECCOMP_RET_KILL
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/* Use a signal handler to emit violations when debugging */
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#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
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# undef SECCOMP_FILTER_FAIL
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# define SECCOMP_FILTER_FAIL SECCOMP_RET_TRAP
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#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
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#if __BYTE_ORDER == __LITTLE_ENDIAN
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# define ARG_LO_OFFSET 0
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# define ARG_HI_OFFSET sizeof(uint32_t)
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#elif __BYTE_ORDER == __BIG_ENDIAN
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# define ARG_LO_OFFSET sizeof(uint32_t)
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# define ARG_HI_OFFSET 0
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#else
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#error "Unknown endianness"
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#endif
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/* Simple helpers to avoid manual errors (but larger BPF programs). */
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#define SC_DENY(_nr, _errno) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ERRNO|(_errno))
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#define SC_ALLOW(_nr) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
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#define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 6), \
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/* load and test syscall argument, low word */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \
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((_arg_val) & 0xFFFFFFFF), 0, 3), \
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/* load and test syscall argument, high word */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \
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(((uint32_t)((uint64_t)(_arg_val) >> 32)) & 0xFFFFFFFF), 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
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/* reload syscall number; all rules expect it in accumulator */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, nr))
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/* Allow if syscall argument contains only values in mask */
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#define SC_ALLOW_ARG_MASK(_nr, _arg_nr, _arg_mask) \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 8), \
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/* load, mask and test syscall argument, low word */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \
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BPF_STMT(BPF_ALU+BPF_AND+BPF_K, ~((_arg_mask) & 0xFFFFFFFF)), \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 4), \
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/* load, mask and test syscall argument, high word */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \
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BPF_STMT(BPF_ALU+BPF_AND+BPF_K, \
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~(((uint32_t)((uint64_t)(_arg_mask) >> 32)) & 0xFFFFFFFF)), \
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 1), \
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
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/* reload syscall number; all rules expect it in accumulator */ \
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
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offsetof(struct seccomp_data, nr))
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/* Syscall filtering set for preauth. */
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static const struct sock_filter preauth_insns[] = {
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/* Ensure the syscall arch convention is as expected. */
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
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offsetof(struct seccomp_data, arch)),
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BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, SECCOMP_AUDIT_ARCH, 1, 0),
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
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/* Load the syscall number for checking. */
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BPF_STMT(BPF_LD+BPF_W+BPF_ABS,
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offsetof(struct seccomp_data, nr)),
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/* Syscalls to non-fatally deny */
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#ifdef __NR_lstat
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SC_DENY(__NR_lstat, EACCES),
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#endif
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#ifdef __NR_lstat64
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SC_DENY(__NR_lstat64, EACCES),
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#endif
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#ifdef __NR_fstat
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SC_DENY(__NR_fstat, EACCES),
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#endif
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#ifdef __NR_fstat64
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SC_DENY(__NR_fstat64, EACCES),
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#endif
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#ifdef __NR_fstatat64
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SC_DENY(__NR_fstatat64, EACCES),
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#endif
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#ifdef __NR_open
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SC_DENY(__NR_open, EACCES),
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#endif
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#ifdef __NR_openat
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SC_DENY(__NR_openat, EACCES),
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#endif
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#ifdef __NR_newfstatat
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SC_DENY(__NR_newfstatat, EACCES),
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#endif
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#ifdef __NR_stat
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SC_DENY(__NR_stat, EACCES),
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#endif
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#ifdef __NR_stat64
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SC_DENY(__NR_stat64, EACCES),
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#endif
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#ifdef __NR_shmget
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SC_DENY(__NR_shmget, EACCES),
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#endif
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#ifdef __NR_shmat
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SC_DENY(__NR_shmat, EACCES),
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#endif
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#ifdef __NR_shmdt
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SC_DENY(__NR_shmdt, EACCES),
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#endif
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#ifdef __NR_ipc
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SC_DENY(__NR_ipc, EACCES),
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#endif
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#ifdef __NR_statx
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SC_DENY(__NR_statx, EACCES),
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#endif
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/* Syscalls to permit */
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#ifdef __NR_brk
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SC_ALLOW(__NR_brk),
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#endif
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#ifdef __NR_clock_gettime
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SC_ALLOW(__NR_clock_gettime),
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#endif
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#ifdef __NR_clock_gettime64
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SC_ALLOW(__NR_clock_gettime64),
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#endif
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#ifdef __NR_close
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SC_ALLOW(__NR_close),
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#endif
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#ifdef __NR_exit
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SC_ALLOW(__NR_exit),
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#endif
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#ifdef __NR_exit_group
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SC_ALLOW(__NR_exit_group),
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#endif
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#ifdef __NR_futex
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SC_ALLOW(__NR_futex),
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#endif
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#ifdef __NR_futex_time64
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SC_ALLOW(__NR_futex_time64),
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#endif
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#ifdef __NR_geteuid
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SC_ALLOW(__NR_geteuid),
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#endif
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#ifdef __NR_geteuid32
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SC_ALLOW(__NR_geteuid32),
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#endif
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#ifdef __NR_getpgid
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SC_ALLOW(__NR_getpgid),
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#endif
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#ifdef __NR_getpid
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SC_ALLOW(__NR_getpid),
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#endif
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#ifdef __NR_getrandom
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SC_ALLOW(__NR_getrandom),
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#endif
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#ifdef __NR_gettid
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SC_ALLOW(__NR_gettid),
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#endif
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#ifdef __NR_gettimeofday
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SC_ALLOW(__NR_gettimeofday),
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#endif
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#ifdef __NR_getuid
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SC_ALLOW(__NR_getuid),
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#endif
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#ifdef __NR_getuid32
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SC_ALLOW(__NR_getuid32),
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#endif
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#ifdef __NR_madvise
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SC_ALLOW(__NR_madvise),
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#endif
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#ifdef __NR_mmap
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SC_ALLOW_ARG_MASK(__NR_mmap, 2, PROT_READ|PROT_WRITE|PROT_NONE),
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#endif
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#ifdef __NR_mmap2
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SC_ALLOW_ARG_MASK(__NR_mmap2, 2, PROT_READ|PROT_WRITE|PROT_NONE),
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#endif
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#ifdef __NR_mprotect
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SC_ALLOW_ARG_MASK(__NR_mprotect, 2, PROT_READ|PROT_WRITE|PROT_NONE),
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#endif
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#ifdef __NR_mremap
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SC_ALLOW(__NR_mremap),
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#endif
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#ifdef __NR_munmap
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SC_ALLOW(__NR_munmap),
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#endif
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#ifdef __NR_nanosleep
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SC_ALLOW(__NR_nanosleep),
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#endif
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#ifdef __NR_clock_nanosleep
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SC_ALLOW(__NR_clock_nanosleep),
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#endif
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#ifdef __NR_clock_nanosleep_time64
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SC_ALLOW(__NR_clock_nanosleep_time64),
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#endif
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#ifdef __NR_clock_gettime64
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SC_ALLOW(__NR_clock_gettime64),
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#endif
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#ifdef __NR__newselect
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SC_ALLOW(__NR__newselect),
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#endif
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#ifdef __NR_ppoll
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SC_ALLOW(__NR_ppoll),
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#endif
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#ifdef __NR_ppoll_time64
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SC_ALLOW(__NR_ppoll_time64),
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#endif
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#ifdef __NR_poll
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SC_ALLOW(__NR_poll),
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#endif
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#ifdef __NR_pselect6
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SC_ALLOW(__NR_pselect6),
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#endif
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#ifdef __NR_pselect6_time64
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SC_ALLOW(__NR_pselect6_time64),
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#endif
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#ifdef __NR_read
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SC_ALLOW(__NR_read),
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#endif
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#ifdef __NR_rt_sigprocmask
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SC_ALLOW(__NR_rt_sigprocmask),
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#endif
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#ifdef __NR_select
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SC_ALLOW(__NR_select),
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#endif
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#ifdef __NR_shutdown
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SC_ALLOW(__NR_shutdown),
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#endif
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#ifdef __NR_sigprocmask
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SC_ALLOW(__NR_sigprocmask),
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#endif
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#ifdef __NR_time
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SC_ALLOW(__NR_time),
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#endif
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#ifdef __NR_write
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SC_ALLOW(__NR_write),
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#endif
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#ifdef __NR_writev
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SC_ALLOW(__NR_writev),
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#endif
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#ifdef __NR_socketcall
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SC_ALLOW_ARG(__NR_socketcall, 0, SYS_SHUTDOWN),
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SC_DENY(__NR_socketcall, EACCES),
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#endif
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#if defined(__NR_ioctl) && defined(__s390__)
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/* Allow ioctls for ICA crypto card on s390 */
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SC_ALLOW_ARG(__NR_ioctl, 1, Z90STAT_STATUS_MASK),
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SC_ALLOW_ARG(__NR_ioctl, 1, ICARSAMODEXPO),
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SC_ALLOW_ARG(__NR_ioctl, 1, ICARSACRT),
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SC_ALLOW_ARG(__NR_ioctl, 1, ZSECSENDCPRB),
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/* Allow ioctls for EP11 crypto card on s390 */
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SC_ALLOW_ARG(__NR_ioctl, 1, ZSENDEP11CPRB),
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#endif
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#if defined(__x86_64__) && defined(__ILP32__) && defined(__X32_SYSCALL_BIT)
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/*
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* On Linux x32, the clock_gettime VDSO falls back to the
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* x86-64 syscall under some circumstances, e.g.
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* https://bugs.debian.org/849923
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*/
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SC_ALLOW(__NR_clock_gettime & ~__X32_SYSCALL_BIT),
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#endif
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/* Default deny */
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BPF_STMT(BPF_RET+BPF_K, SECCOMP_FILTER_FAIL),
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};
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static const struct sock_fprog preauth_program = {
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.len = (unsigned short)(sizeof(preauth_insns)/sizeof(preauth_insns[0])),
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.filter = (struct sock_filter *)preauth_insns,
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};
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struct ssh_sandbox {
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pid_t child_pid;
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};
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struct ssh_sandbox *
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ssh_sandbox_init(struct monitor *monitor)
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{
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struct ssh_sandbox *box;
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/*
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* Strictly, we don't need to maintain any state here but we need
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* to return non-NULL to satisfy the API.
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*/
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debug3("%s: preparing seccomp filter sandbox", __func__);
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box = xcalloc(1, sizeof(*box));
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box->child_pid = 0;
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return box;
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}
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#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
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extern struct monitor *pmonitor;
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void mm_log_handler(LogLevel level, int forced, const char *msg, void *ctx);
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static void
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ssh_sandbox_violation(int signum, siginfo_t *info, void *void_context)
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{
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char msg[256];
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snprintf(msg, sizeof(msg),
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"%s: unexpected system call (arch:0x%x,syscall:%d @ %p)",
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__func__, info->si_arch, info->si_syscall, info->si_call_addr);
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mm_log_handler(SYSLOG_LEVEL_FATAL, 0, msg, pmonitor);
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_exit(1);
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}
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static void
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ssh_sandbox_child_debugging(void)
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{
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struct sigaction act;
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sigset_t mask;
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debug3("%s: installing SIGSYS handler", __func__);
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memset(&act, 0, sizeof(act));
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sigemptyset(&mask);
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sigaddset(&mask, SIGSYS);
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act.sa_sigaction = &ssh_sandbox_violation;
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act.sa_flags = SA_SIGINFO;
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if (sigaction(SIGSYS, &act, NULL) == -1)
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fatal("%s: sigaction(SIGSYS): %s", __func__, strerror(errno));
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if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
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fatal("%s: sigprocmask(SIGSYS): %s",
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__func__, strerror(errno));
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}
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#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
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void
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ssh_sandbox_child(struct ssh_sandbox *box)
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{
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struct rlimit rl_zero, rl_one = {.rlim_cur = 1, .rlim_max = 1};
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int nnp_failed = 0;
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/* Set rlimits for completeness if possible. */
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rl_zero.rlim_cur = rl_zero.rlim_max = 0;
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if (setrlimit(RLIMIT_FSIZE, &rl_zero) == -1)
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fatal("%s: setrlimit(RLIMIT_FSIZE, { 0, 0 }): %s",
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__func__, strerror(errno));
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/*
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* Cannot use zero for nfds, because poll(2) will fail with
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* errno=EINVAL if npfds>RLIMIT_NOFILE.
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*/
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if (setrlimit(RLIMIT_NOFILE, &rl_one) == -1)
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fatal("%s: setrlimit(RLIMIT_NOFILE, { 0, 0 }): %s",
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__func__, strerror(errno));
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if (setrlimit(RLIMIT_NPROC, &rl_zero) == -1)
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fatal("%s: setrlimit(RLIMIT_NPROC, { 0, 0 }): %s",
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__func__, strerror(errno));
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#ifdef SANDBOX_SECCOMP_FILTER_DEBUG
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ssh_sandbox_child_debugging();
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#endif /* SANDBOX_SECCOMP_FILTER_DEBUG */
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debug3("%s: setting PR_SET_NO_NEW_PRIVS", __func__);
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if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == -1) {
|
|
debug("%s: prctl(PR_SET_NO_NEW_PRIVS): %s",
|
|
__func__, strerror(errno));
|
|
nnp_failed = 1;
|
|
}
|
|
debug3("%s: attaching seccomp filter program", __func__);
|
|
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &preauth_program) == -1)
|
|
debug("%s: prctl(PR_SET_SECCOMP): %s",
|
|
__func__, strerror(errno));
|
|
else if (nnp_failed)
|
|
fatal("%s: SECCOMP_MODE_FILTER activated but "
|
|
"PR_SET_NO_NEW_PRIVS failed", __func__);
|
|
}
|
|
|
|
void
|
|
ssh_sandbox_parent_finish(struct ssh_sandbox *box)
|
|
{
|
|
free(box);
|
|
debug3("%s: finished", __func__);
|
|
}
|
|
|
|
void
|
|
ssh_sandbox_parent_preauth(struct ssh_sandbox *box, pid_t child_pid)
|
|
{
|
|
box->child_pid = child_pid;
|
|
}
|
|
|
|
#endif /* SANDBOX_SECCOMP_FILTER */
|