1816494330
This change has the following effects, in order of descreasing importance: 1) Prevent a stack buffer overflow 2) Do not append an unnecessary NULL to an anyway binary buffer, which is writing one byte past client_digest when caller is: chap_string_to_hex(client_digest, chap_r, strlen(chap_r)); The latter was found by KASAN (see below) when input value hes expected size (32 hex chars), and further analysis revealed a stack buffer overflow can happen when network-received value is longer, allowing an unauthenticated remote attacker to smash up to 17 bytes after destination buffer (16 bytes attacker-controlled and one null). As switching to hex2bin requires specifying destination buffer length, and does not internally append any null, it solves both issues. This addresses CVE-2018-14633. Beyond this: - Validate received value length and check hex2bin accepted the input, to log this rejection reason instead of just failing authentication. - Only log received CHAP_R and CHAP_C values once they passed sanity checks. ================================================================== BUG: KASAN: stack-out-of-bounds in chap_string_to_hex+0x32/0x60 [iscsi_target_mod] Write of size 1 at addr ffff8801090ef7c8 by task kworker/0:0/1021 CPU: 0 PID: 1021 Comm: kworker/0:0 Tainted: G O 4.17.8kasan.sess.connops+ #2 Hardware name: To be filled by O.E.M. To be filled by O.E.M./Aptio CRB, BIOS 5.6.5 05/19/2014 Workqueue: events iscsi_target_do_login_rx [iscsi_target_mod] Call Trace: dump_stack+0x71/0xac print_address_description+0x65/0x22e ? chap_string_to_hex+0x32/0x60 [iscsi_target_mod] kasan_report.cold.6+0x241/0x2fd chap_string_to_hex+0x32/0x60 [iscsi_target_mod] chap_server_compute_md5.isra.2+0x2cb/0x860 [iscsi_target_mod] ? chap_binaryhex_to_asciihex.constprop.5+0x50/0x50 [iscsi_target_mod] ? ftrace_caller_op_ptr+0xe/0xe ? __orc_find+0x6f/0xc0 ? unwind_next_frame+0x231/0x850 ? kthread+0x1a0/0x1c0 ? ret_from_fork+0x35/0x40 ? ret_from_fork+0x35/0x40 ? iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod] ? deref_stack_reg+0xd0/0xd0 ? iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod] ? is_module_text_address+0xa/0x11 ? kernel_text_address+0x4c/0x110 ? __save_stack_trace+0x82/0x100 ? ret_from_fork+0x35/0x40 ? save_stack+0x8c/0xb0 ? 0xffffffffc1660000 ? iscsi_target_do_login+0x155/0x8d0 [iscsi_target_mod] ? iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod] ? process_one_work+0x35c/0x640 ? worker_thread+0x66/0x5d0 ? kthread+0x1a0/0x1c0 ? ret_from_fork+0x35/0x40 ? iscsi_update_param_value+0x80/0x80 [iscsi_target_mod] ? iscsit_release_cmd+0x170/0x170 [iscsi_target_mod] chap_main_loop+0x172/0x570 [iscsi_target_mod] ? chap_server_compute_md5.isra.2+0x860/0x860 [iscsi_target_mod] ? rx_data+0xd6/0x120 [iscsi_target_mod] ? iscsit_print_session_params+0xd0/0xd0 [iscsi_target_mod] ? cyc2ns_read_begin.part.2+0x90/0x90 ? _raw_spin_lock_irqsave+0x25/0x50 ? memcmp+0x45/0x70 iscsi_target_do_login+0x875/0x8d0 [iscsi_target_mod] ? iscsi_target_check_first_request.isra.5+0x1a0/0x1a0 [iscsi_target_mod] ? del_timer+0xe0/0xe0 ? memset+0x1f/0x40 ? flush_sigqueue+0x29/0xd0 iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod] ? iscsi_target_nego_release+0x80/0x80 [iscsi_target_mod] ? iscsi_target_restore_sock_callbacks+0x130/0x130 [iscsi_target_mod] process_one_work+0x35c/0x640 worker_thread+0x66/0x5d0 ? flush_rcu_work+0x40/0x40 kthread+0x1a0/0x1c0 ? kthread_bind+0x30/0x30 ret_from_fork+0x35/0x40 The buggy address belongs to the page: page:ffffea0004243bc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x17fffc000000000() raw: 017fffc000000000 0000000000000000 0000000000000000 00000000ffffffff raw: ffffea0004243c20 ffffea0004243ba0 0000000000000000 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801090ef680: f2 f2 f2 f2 f2 f2 f2 01 f2 f2 f2 f2 f2 f2 f2 00 ffff8801090ef700: f2 f2 f2 f2 f2 f2 f2 00 02 f2 f2 f2 f2 f2 f2 00 >ffff8801090ef780: 00 f2 f2 f2 f2 f2 f2 00 00 f2 f2 f2 f2 f2 f2 00 ^ ffff8801090ef800: 00 f2 f2 f2 f2 f2 f2 00 00 00 00 02 f2 f2 f2 f2 ffff8801090ef880: f2 f2 f2 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00 ================================================================== Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com> Reviewed-by: Mike Christie <mchristi@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.