Fix CVE-2018-14633
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From 1816494330a83f2a064499d8ed2797045641f92c Mon Sep 17 00:00:00 2001
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From: Vincent Pelletier <plr.vincent@gmail.com>
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Date: Sun, 9 Sep 2018 04:09:26 +0000
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Subject: scsi: target: iscsi: Use hex2bin instead of a re-implementation
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This change has the following effects, in order of descreasing importance:
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1) Prevent a stack buffer overflow
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2) Do not append an unnecessary NULL to an anyway binary buffer, which
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is writing one byte past client_digest when caller is:
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chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
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The latter was found by KASAN (see below) when input value hes expected size
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(32 hex chars), and further analysis revealed a stack buffer overflow can
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happen when network-received value is longer, allowing an unauthenticated
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remote attacker to smash up to 17 bytes after destination buffer (16 bytes
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attacker-controlled and one null). As switching to hex2bin requires
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specifying destination buffer length, and does not internally append any null,
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it solves both issues.
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This addresses CVE-2018-14633.
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Beyond this:
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- Validate received value length and check hex2bin accepted the input, to log
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this rejection reason instead of just failing authentication.
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- Only log received CHAP_R and CHAP_C values once they passed sanity checks.
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==================================================================
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BUG: KASAN: stack-out-of-bounds in chap_string_to_hex+0x32/0x60 [iscsi_target_mod]
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Write of size 1 at addr ffff8801090ef7c8 by task kworker/0:0/1021
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CPU: 0 PID: 1021 Comm: kworker/0:0 Tainted: G O 4.17.8kasan.sess.connops+ #2
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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
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Workqueue: events iscsi_target_do_login_rx [iscsi_target_mod]
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Call Trace:
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dump_stack+0x71/0xac
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print_address_description+0x65/0x22e
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? chap_string_to_hex+0x32/0x60 [iscsi_target_mod]
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kasan_report.cold.6+0x241/0x2fd
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chap_string_to_hex+0x32/0x60 [iscsi_target_mod]
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chap_server_compute_md5.isra.2+0x2cb/0x860 [iscsi_target_mod]
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? chap_binaryhex_to_asciihex.constprop.5+0x50/0x50 [iscsi_target_mod]
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? ftrace_caller_op_ptr+0xe/0xe
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? __orc_find+0x6f/0xc0
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? unwind_next_frame+0x231/0x850
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? kthread+0x1a0/0x1c0
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? ret_from_fork+0x35/0x40
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? ret_from_fork+0x35/0x40
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? iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod]
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? deref_stack_reg+0xd0/0xd0
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? iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod]
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? is_module_text_address+0xa/0x11
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? kernel_text_address+0x4c/0x110
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? __save_stack_trace+0x82/0x100
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? ret_from_fork+0x35/0x40
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? save_stack+0x8c/0xb0
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? 0xffffffffc1660000
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? iscsi_target_do_login+0x155/0x8d0 [iscsi_target_mod]
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? iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod]
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? process_one_work+0x35c/0x640
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? worker_thread+0x66/0x5d0
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? kthread+0x1a0/0x1c0
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? ret_from_fork+0x35/0x40
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? iscsi_update_param_value+0x80/0x80 [iscsi_target_mod]
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? iscsit_release_cmd+0x170/0x170 [iscsi_target_mod]
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chap_main_loop+0x172/0x570 [iscsi_target_mod]
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? chap_server_compute_md5.isra.2+0x860/0x860 [iscsi_target_mod]
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? rx_data+0xd6/0x120 [iscsi_target_mod]
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? iscsit_print_session_params+0xd0/0xd0 [iscsi_target_mod]
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? cyc2ns_read_begin.part.2+0x90/0x90
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? _raw_spin_lock_irqsave+0x25/0x50
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? memcmp+0x45/0x70
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iscsi_target_do_login+0x875/0x8d0 [iscsi_target_mod]
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? iscsi_target_check_first_request.isra.5+0x1a0/0x1a0 [iscsi_target_mod]
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? del_timer+0xe0/0xe0
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? memset+0x1f/0x40
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? flush_sigqueue+0x29/0xd0
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iscsi_target_do_login_rx+0x3bc/0x4c0 [iscsi_target_mod]
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? iscsi_target_nego_release+0x80/0x80 [iscsi_target_mod]
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? iscsi_target_restore_sock_callbacks+0x130/0x130 [iscsi_target_mod]
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process_one_work+0x35c/0x640
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worker_thread+0x66/0x5d0
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? flush_rcu_work+0x40/0x40
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kthread+0x1a0/0x1c0
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? kthread_bind+0x30/0x30
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ret_from_fork+0x35/0x40
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The buggy address belongs to the page:
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page:ffffea0004243bc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
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flags: 0x17fffc000000000()
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raw: 017fffc000000000 0000000000000000 0000000000000000 00000000ffffffff
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raw: ffffea0004243c20 ffffea0004243ba0 0000000000000000 0000000000000000
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page dumped because: kasan: bad access detected
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Memory state around the buggy address:
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ffff8801090ef680: f2 f2 f2 f2 f2 f2 f2 01 f2 f2 f2 f2 f2 f2 f2 00
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ffff8801090ef700: f2 f2 f2 f2 f2 f2 f2 00 02 f2 f2 f2 f2 f2 f2 00
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>ffff8801090ef780: 00 f2 f2 f2 f2 f2 f2 00 00 f2 f2 f2 f2 f2 f2 00
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^
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ffff8801090ef800: 00 f2 f2 f2 f2 f2 f2 00 00 00 00 02 f2 f2 f2 f2
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ffff8801090ef880: f2 f2 f2 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00
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==================================================================
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Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
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Reviewed-by: Mike Christie <mchristi@redhat.com>
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Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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---
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drivers/target/iscsi/iscsi_target_auth.c | 30 ++++++++++++++----------------
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1 file changed, 14 insertions(+), 16 deletions(-)
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diff --git a/drivers/target/iscsi/iscsi_target_auth.c b/drivers/target/iscsi/iscsi_target_auth.c
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index 9518ffd8b8ba..6c3b4c022894 100644
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--- a/drivers/target/iscsi/iscsi_target_auth.c
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+++ b/drivers/target/iscsi/iscsi_target_auth.c
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@@ -26,18 +26,6 @@
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#include "iscsi_target_nego.h"
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#include "iscsi_target_auth.h"
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-static int chap_string_to_hex(unsigned char *dst, unsigned char *src, int len)
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-{
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- int j = DIV_ROUND_UP(len, 2), rc;
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-
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- rc = hex2bin(dst, src, j);
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- if (rc < 0)
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- pr_debug("CHAP string contains non hex digit symbols\n");
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-
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- dst[j] = '\0';
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- return j;
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-}
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-
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static void chap_binaryhex_to_asciihex(char *dst, char *src, int src_len)
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{
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int i;
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@@ -248,9 +236,16 @@ static int chap_server_compute_md5(
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pr_err("Could not find CHAP_R.\n");
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goto out;
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}
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+ if (strlen(chap_r) != MD5_SIGNATURE_SIZE * 2) {
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+ pr_err("Malformed CHAP_R\n");
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+ goto out;
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+ }
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+ if (hex2bin(client_digest, chap_r, MD5_SIGNATURE_SIZE) < 0) {
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+ pr_err("Malformed CHAP_R\n");
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+ goto out;
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+ }
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pr_debug("[server] Got CHAP_R=%s\n", chap_r);
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- chap_string_to_hex(client_digest, chap_r, strlen(chap_r));
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tfm = crypto_alloc_shash("md5", 0, 0);
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if (IS_ERR(tfm)) {
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@@ -349,9 +344,7 @@ static int chap_server_compute_md5(
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pr_err("Could not find CHAP_C.\n");
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goto out;
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}
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- pr_debug("[server] Got CHAP_C=%s\n", challenge);
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- challenge_len = chap_string_to_hex(challenge_binhex, challenge,
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- strlen(challenge));
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+ challenge_len = DIV_ROUND_UP(strlen(challenge), 2);
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if (!challenge_len) {
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pr_err("Unable to convert incoming challenge\n");
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goto out;
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@@ -360,6 +353,11 @@ static int chap_server_compute_md5(
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pr_err("CHAP_C exceeds maximum binary size of 1024 bytes\n");
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goto out;
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}
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+ if (hex2bin(challenge_binhex, challenge, challenge_len) < 0) {
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+ pr_err("Malformed CHAP_C\n");
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+ goto out;
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+ }
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+ pr_debug("[server] Got CHAP_C=%s\n", challenge);
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/*
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* During mutual authentication, the CHAP_C generated by the
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* initiator must not match the original CHAP_C generated by
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--
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cgit 1.2-0.3.lf.el7
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From 8c39e2699f8acb2e29782a834e56306da24937fe Mon Sep 17 00:00:00 2001
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From: Vincent Pelletier <plr.vincent@gmail.com>
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Date: Sun, 9 Sep 2018 04:09:27 +0000
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Subject: scsi: target: iscsi: Use bin2hex instead of a re-implementation
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Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
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Reviewed-by: Mike Christie <mchristi@redhat.com>
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Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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---
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drivers/target/iscsi/iscsi_target_auth.c | 15 +++------------
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1 file changed, 3 insertions(+), 12 deletions(-)
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diff --git a/drivers/target/iscsi/iscsi_target_auth.c b/drivers/target/iscsi/iscsi_target_auth.c
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index 6c3b4c022894..4e680d753941 100644
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--- a/drivers/target/iscsi/iscsi_target_auth.c
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+++ b/drivers/target/iscsi/iscsi_target_auth.c
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@@ -26,15 +26,6 @@
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#include "iscsi_target_nego.h"
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#include "iscsi_target_auth.h"
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-static void chap_binaryhex_to_asciihex(char *dst, char *src, int src_len)
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-{
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- int i;
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-
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- for (i = 0; i < src_len; i++) {
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- sprintf(&dst[i*2], "%02x", (int) src[i] & 0xff);
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- }
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-}
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-
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static int chap_gen_challenge(
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struct iscsi_conn *conn,
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int caller,
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@@ -50,7 +41,7 @@ static int chap_gen_challenge(
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ret = get_random_bytes_wait(chap->challenge, CHAP_CHALLENGE_LENGTH);
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if (unlikely(ret))
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return ret;
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- chap_binaryhex_to_asciihex(challenge_asciihex, chap->challenge,
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+ bin2hex(challenge_asciihex, chap->challenge,
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CHAP_CHALLENGE_LENGTH);
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/*
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* Set CHAP_C, and copy the generated challenge into c_str.
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@@ -289,7 +280,7 @@ static int chap_server_compute_md5(
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goto out;
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}
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- chap_binaryhex_to_asciihex(response, server_digest, MD5_SIGNATURE_SIZE);
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+ bin2hex(response, server_digest, MD5_SIGNATURE_SIZE);
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pr_debug("[server] MD5 Server Digest: %s\n", response);
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if (memcmp(server_digest, client_digest, MD5_SIGNATURE_SIZE) != 0) {
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@@ -411,7 +402,7 @@ static int chap_server_compute_md5(
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/*
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* Convert response from binary hex to ascii hext.
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*/
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- chap_binaryhex_to_asciihex(response, digest, MD5_SIGNATURE_SIZE);
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+ bin2hex(response, digest, MD5_SIGNATURE_SIZE);
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*nr_out_len += sprintf(nr_out_ptr + *nr_out_len, "CHAP_R=0x%s",
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response);
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*nr_out_len += 1;
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--
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cgit 1.2-0.3.lf.el7
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@ -628,6 +628,9 @@ Patch504: xsa270.patch
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Patch506: 0001-random-add-a-config-option-to-trust-the-CPU-s-hwrng.patch
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Patch507: 0001-random-make-CPU-trust-a-boot-parameter.patch
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# CVE-2018-14633 rhbz 1626035 1632185
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Patch508: CVE-2018-14633.patch
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# END OF PATCH DEFINITIONS
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%endif
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@ -1877,6 +1880,9 @@ fi
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#
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#
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%changelog
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* Mon Sep 24 2018 Justin M. Forbes <jforbes@fedoraproject.org>
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- Fix CVE-2018-14633 (rhbz 1626035 1632185)
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* Thu Sep 20 2018 Laura Abbott <labbott@redhat.com> - 4.18.9-200
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- Linux v4.18.9
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- Fixes CVE-2018-17182 (rhbz 1631205 1631206)
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