kernel/linux.git/security/keys, branch v3.2.95

KEYS: don't let add_key() update an uninstantiated key

2017-11-11T13:34:38+00:00

commit 60ff5b2f547af3828aebafd54daded44cfb0807a upstream. Currently, when passed a key that already exists, add_key() will call the key's ->update() method if such exists. But this is heavily broken in the case where the key is uninstantiated because it doesn't call __key_instantiate_and_link(). Consequently, it doesn't do most of the things that are supposed to happen when the key is instantiated, such as setting the instantiation state, clearing KEY_FLAG_USER_CONSTRUCT and awakening tasks waiting on it, and incrementing key->user->nikeys. It also never takes key_construction_mutex, which means that ->instantiate() can run concurrently with ->update() on the same key. In the case of the "user" and "logon" key types this causes a memory leak, at best. Maybe even worse, the ->update() methods of the "encrypted" and "trusted" key types actually just dereference a NULL pointer when passed an uninstantiated key. Change key_create_or_update() to wait interruptibly for the key to finish construction before continuing. This patch only affects *uninstantiated* keys. For now we still allow a negatively instantiated key to be updated (thereby positively instantiating it), although that's broken too (the next patch fixes it) and I'm not sure that anyone actually uses that functionality either. Here is a simple reproducer for the bug using the "encrypted" key type (requires CONFIG_ENCRYPTED_KEYS=y), though as noted above the bug pertained to more than just the "encrypted" key type: #include #include #include int main(void) { int ringid = keyctl_join_session_keyring(NULL); if (fork()) { for (;;) { const char payload[] = "update user:foo 32"; usleep(rand() % 10000); add_key("encrypted", "desc", payload, sizeof(payload), ringid); keyctl_clear(ringid); } } else { for (;;) request_key("encrypted", "desc", "callout_info", ringid); } } It causes: BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 IP: encrypted_update+0xb0/0x170 PGD 7a178067 P4D 7a178067 PUD 77269067 PMD 0 PREEMPT SMP CPU: 0 PID: 340 Comm: reproduce Tainted: G D 4.14.0-rc1-00025-g428490e38b2e #796 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff8a467a39a340 task.stack: ffffb15c40770000 RIP: 0010:encrypted_update+0xb0/0x170 RSP: 0018:ffffb15c40773de8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff8a467a275b00 RCX: 0000000000000000 RDX: 0000000000000005 RSI: ffff8a467a275b14 RDI: ffffffffb742f303 RBP: ffffb15c40773e20 R08: 0000000000000000 R09: ffff8a467a275b17 R10: 0000000000000020 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: ffff8a4677057180 R15: ffff8a467a275b0f FS: 00007f5d7fb08700(0000) GS:ffff8a467f200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 0000000077262005 CR4: 00000000001606f0 Call Trace: key_create_or_update+0x2bc/0x460 SyS_add_key+0x10c/0x1d0 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x7f5d7f211259 RSP: 002b:00007ffed03904c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000f8 RAX: ffffffffffffffda RBX: 000000003b2a7955 RCX: 00007f5d7f211259 RDX: 00000000004009e4 RSI: 00000000004009ff RDI: 0000000000400a04 RBP: 0000000068db8bad R08: 000000003b2a7955 R09: 0000000000000004 R10: 000000000000001a R11: 0000000000000246 R12: 0000000000400868 R13: 00007ffed03905d0 R14: 0000000000000000 R15: 0000000000000000 Code: 77 28 e8 64 34 1f 00 45 31 c0 31 c9 48 8d 55 c8 48 89 df 48 8d 75 d0 e8 ff f9 ff ff 85 c0 41 89 c4 0f 88 84 00 00 00 4c 8b 7d c8 <49> 8b 75 18 4c 89 ff e8 24 f8 ff ff 85 c0 41 89 c4 78 6d 49 8b RIP: encrypted_update+0xb0/0x170 RSP: ffffb15c40773de8 CR2: 0000000000000018 Reported-by: Eric Biggers Signed-off-by: David Howells cc: Eric Biggers [bwh: Backported to 3.2: - Use the 'error' label to return, not 'error_free_prep' - Adjust context] Signed-off-by: Ben Hutchings

KEYS: fix dereferencing NULL payload with nonzero length

2017-09-15T17:30:52+00:00

commit 5649645d725c73df4302428ee4e02c869248b4c5 upstream. sys_add_key() and the KEYCTL_UPDATE operation of sys_keyctl() allowed a NULL payload with nonzero length to be passed to the key type's ->preparse(), ->instantiate(), and/or ->update() methods. Various key types including asymmetric, cifs.idmap, cifs.spnego, and pkcs7_test did not handle this case, allowing an unprivileged user to trivially cause a NULL pointer dereference (kernel oops) if one of these key types was present. Fix it by doing the copy_from_user() when 'plen' is nonzero rather than when '_payload' is non-NULL, causing the syscall to fail with EFAULT as expected when an invalid buffer is specified. Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: James Morris [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

KEYS: Change the name of the dead type to ".dead" to prevent user access

2017-07-18T17:38:43+00:00

commit c1644fe041ebaf6519f6809146a77c3ead9193af upstream. This fixes CVE-2017-6951. Userspace should not be able to do things with the "dead" key type as it doesn't have some of the helper functions set upon it that the kernel needs. Attempting to use it may cause the kernel to crash. Fix this by changing the name of the type to ".dead" so that it's rejected up front on userspace syscalls by key_get_type_from_user(). Though this doesn't seem to affect recent kernels, it does affect older ones, certainly those prior to: commit c06cfb08b88dfbe13be44a69ae2fdc3a7c902d81 Author: David Howells Date: Tue Sep 16 17:36:06 2014 +0100 KEYS: Remove key_type::match in favour of overriding default by match_preparse which went in before 3.18-rc1. Signed-off-by: David Howells Signed-off-by: Ben Hutchings

KEYS: fix keyctl_set_reqkey_keyring() to not leak thread keyrings

2017-06-05T20:13:54+00:00

commit c9f838d104fed6f2f61d68164712e3204bf5271b upstream. This fixes CVE-2017-7472. Running the following program as an unprivileged user exhausts kernel memory by leaking thread keyrings: #include int main() { for (;;) keyctl_set_reqkey_keyring(KEY_REQKEY_DEFL_THREAD_KEYRING); } Fix it by only creating a new thread keyring if there wasn't one before. To make things more consistent, make install_thread_keyring_to_cred() and install_process_keyring_to_cred() both return 0 if the corresponding keyring is already present. Fixes: d84f4f992cbd ("CRED: Inaugurate COW credentials") Signed-off-by: Eric Biggers Signed-off-by: David Howells [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

KEYS: Disallow keyrings beginning with '.' to be joined as session keyrings

2017-06-05T20:13:53+00:00

commit ee8f844e3c5a73b999edf733df1c529d6503ec2f upstream. This fixes CVE-2016-9604. Keyrings whose name begin with a '.' are special internal keyrings and so userspace isn't allowed to create keyrings by this name to prevent shadowing. However, the patch that added the guard didn't fix KEYCTL_JOIN_SESSION_KEYRING. Not only can that create dot-named keyrings, it can also subscribe to them as a session keyring if they grant SEARCH permission to the user. This, for example, allows a root process to set .builtin_trusted_keys as its session keyring, at which point it has full access because now the possessor permissions are added. This permits root to add extra public keys, thereby bypassing module verification. This also affects kexec and IMA. This can be tested by (as root): keyctl session .builtin_trusted_keys keyctl add user a a @s keyctl list @s which on my test box gives me: 2 keys in keyring: 180010936: ---lswrv 0 0 asymmetric: Build time autogenerated kernel key: ae3d4a31b82daa8e1a75b49dc2bba949fd992a05 801382539: --alswrv 0 0 user: a Fix this by rejecting names beginning with a '.' in the keyctl. Signed-off-by: David Howells Acked-by: Mimi Zohar cc: linux-ima-devel@lists.sourceforge.net Signed-off-by: Ben Hutchings

KEYS: Reinstate EPERM for a key type name beginning with a '.'

2017-06-05T20:13:52+00:00

commit 54e2c2c1a9d6cbb270b0999a38545fa9a69bee43 upstream. Reinstate the generation of EPERM for a key type name beginning with a '.' in a userspace call. Types whose name begins with a '.' are internal only. The test was removed by: commit a4e3b8d79a5c6d40f4a9703abf7fe3abcc6c3b8d Author: Mimi Zohar Date: Thu May 22 14:02:23 2014 -0400 Subject: KEYS: special dot prefixed keyring name bug fix I think we want to keep the restriction on type name so that userspace can't add keys of a special internal type. Note that removal of the test causes several of the tests in the keyutils testsuite to fail. Signed-off-by: David Howells Acked-by: Vivek Goyal cc: Mimi Zohar Signed-off-by: Ben Hutchings

KEYS: special dot prefixed keyring name bug fix

2017-06-05T20:13:52+00:00

commit a4e3b8d79a5c6d40f4a9703abf7fe3abcc6c3b8d upstream. Dot prefixed keyring names are supposed to be reserved for the kernel, but add_key() calls key_get_type_from_user(), which incorrectly verifies the 'type' field, not the 'description' field. This patch verifies the 'description' field isn't dot prefixed, when creating a new keyring, and removes the dot prefix test in key_get_type_from_user(). Changelog v6: - whitespace and other cleanup Changelog v5: - Only prevent userspace from creating a dot prefixed keyring, not regular keys - Dmitry Reported-by: Dmitry Kasatkin Signed-off-by: Mimi Zohar Acked-by: David Howells [bwh: Backported to 3.2: adjust context, indentation] Signed-off-by: Ben Hutchings

KEYS: Fix an error code in request_master_key()

2017-06-05T20:13:48+00:00

commit 57cb17e764ba0aaa169d07796acce54ccfbc6cae upstream. This function has two callers and neither are able to handle a NULL return. Really, -EINVAL is the correct thing return here anyway. This fixes some static checker warnings like: security/keys/encrypted-keys/encrypted.c:709 encrypted_key_decrypt() error: uninitialized symbol 'master_key'. Fixes: 7e70cb497850 ("keys: add new key-type encrypted") Signed-off-by: Dan Carpenter Acked-by: Mimi Zohar Signed-off-by: James Morris Signed-off-by: Ben Hutchings

keys: Guard against null match function in keyring_search_aux()

2017-04-04T21:18:33+00:00

The "dead" key type has no match operation, and a search for keys of this type can cause a null dereference in keyring_search_aux(). keyring_search() has a check for this, but request_keyring_and_link() does not. Move the check into keyring_search_aux(), covering both of them. This was fixed upstream by commit c06cfb08b88d ("KEYS: Remove key_type::match in favour of overriding default by match_preparse"), part of a series of large changes that are not suitable for backporting. CVE-2017-2647 / CVE-2017-6951 Reported-by: Igor Redko Reported-by: Andrey Ryabinin References: https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-2647 Reported-by: idl3r References: https://www.spinics.net/lists/keyrings/msg01845.html Signed-off-by: Ben Hutchings Cc: David Howells

KEYS: Fix short sprintf buffer in /proc/keys show function

2016-11-20T01:01:43+00:00

commit 03dab869b7b239c4e013ec82aea22e181e441cfc upstream. This fixes CVE-2016-7042. Fix a short sprintf buffer in proc_keys_show(). If the gcc stack protector is turned on, this can cause a panic due to stack corruption. The problem is that xbuf[] is not big enough to hold a 64-bit timeout rendered as weeks: (gdb) p 0xffffffffffffffffULL/(60*60*24*7) $2 = 30500568904943 That's 14 chars plus NUL, not 11 chars plus NUL. Expand the buffer to 16 chars. I think the unpatched code apparently works if the stack-protector is not enabled because on a 32-bit machine the buffer won't be overflowed and on a 64-bit machine there's a 64-bit aligned pointer at one side and an int that isn't checked again on the other side. The panic incurred looks something like: Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81352ebe CPU: 0 PID: 1692 Comm: reproducer Not tainted 4.7.2-201.fc24.x86_64 #1 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 0000000000000086 00000000fbbd2679 ffff8800a044bc00 ffffffff813d941f ffffffff81a28d58 ffff8800a044bc98 ffff8800a044bc88 ffffffff811b2cb6 ffff880000000010 ffff8800a044bc98 ffff8800a044bc30 00000000fbbd2679 Call Trace: [] dump_stack+0x63/0x84 [] panic+0xde/0x22a [] ? proc_keys_show+0x3ce/0x3d0 [] __stack_chk_fail+0x19/0x30 [] proc_keys_show+0x3ce/0x3d0 [] ? key_validate+0x50/0x50 [] ? key_default_cmp+0x20/0x20 [] seq_read+0x2cc/0x390 [] proc_reg_read+0x42/0x70 [] __vfs_read+0x37/0x150 [] ? security_file_permission+0xa0/0xc0 [] vfs_read+0x96/0x130 [] SyS_read+0x55/0xc0 [] entry_SYSCALL_64_fastpath+0x1a/0xa4 Reported-by: Ondrej Kozina Signed-off-by: David Howells Tested-by: Ondrej Kozina Signed-off-by: James Morris Signed-off-by: Ben Hutchings