kernel/linux.git/security/integrity/ima/ima_main.c, branch linux-4.16.y

ima: Fallback to the builtin hash algorithm

2018-05-30T06:17:30+00:00

[ Upstream commit ab60368ab6a452466885ef4edf0cefd089465132 ] IMA requires having it's hash algorithm be compiled-in due to it's early use. The default IMA algorithm is protected by Kconfig to be compiled-in. The ima_hash kernel parameter allows to choose the hash algorithm. When the specified algorithm is not available or available as a module, IMA initialization fails, which leads to a kernel panic (mknodat syscall calls ima_post_path_mknod()). Therefore as fallback we force IMA to use the default builtin Kconfig hash algorithm. Fixed crash: $ grep CONFIG_CRYPTO_MD4 .config CONFIG_CRYPTO_MD4=m [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-4.12.14-2.3-default root=UUID=74ae8202-9ca7-4e39-813b-22287ec52f7a video=1024x768-16 plymouth.ignore-serial-consoles console=ttyS0 console=tty resume=/dev/disk/by-path/pci-0000:00:07.0-part3 splash=silent showopts ima_hash=md4 ... [ 1.545190] ima: Can not allocate md4 (reason: -2) ... [ 2.610120] BUG: unable to handle kernel NULL pointer dereference at (null) [ 2.611903] IP: ima_match_policy+0x23/0x390 [ 2.612967] PGD 0 P4D 0 [ 2.613080] Oops: 0000 [#1] SMP [ 2.613080] Modules linked in: autofs4 [ 2.613080] Supported: Yes [ 2.613080] CPU: 0 PID: 1 Comm: systemd Not tainted 4.12.14-2.3-default #1 [ 2.613080] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 [ 2.613080] task: ffff88003e2d0040 task.stack: ffffc90000190000 [ 2.613080] RIP: 0010:ima_match_policy+0x23/0x390 [ 2.613080] RSP: 0018:ffffc90000193e88 EFLAGS: 00010296 [ 2.613080] RAX: 0000000000000000 RBX: 000000000000000c RCX: 0000000000000004 [ 2.613080] RDX: 0000000000000010 RSI: 0000000000000001 RDI: ffff880037071728 [ 2.613080] RBP: 0000000000008000 R08: 0000000000000000 R09: 0000000000000000 [ 2.613080] R10: 0000000000000008 R11: 61c8864680b583eb R12: 00005580ff10086f [ 2.613080] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000008000 [ 2.613080] FS: 00007f5c1da08940(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000 [ 2.613080] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2.613080] CR2: 0000000000000000 CR3: 0000000037002000 CR4: 00000000003406f0 [ 2.613080] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 2.613080] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 2.613080] Call Trace: [ 2.613080] ? shmem_mknod+0xbf/0xd0 [ 2.613080] ima_post_path_mknod+0x1c/0x40 [ 2.613080] SyS_mknod+0x210/0x220 [ 2.613080] entry_SYSCALL_64_fastpath+0x1a/0xa5 [ 2.613080] RIP: 0033:0x7f5c1bfde570 [ 2.613080] RSP: 002b:00007ffde1c90dc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000085 [ 2.613080] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5c1bfde570 [ 2.613080] RDX: 0000000000000000 RSI: 0000000000008000 RDI: 00005580ff10086f [ 2.613080] RBP: 00007ffde1c91040 R08: 00005580ff10086f R09: 0000000000000000 [ 2.613080] R10: 0000000000104000 R11: 0000000000000246 R12: 00005580ffb99660 [ 2.613080] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000002 [ 2.613080] Code: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 41 56 44 8d 14 09 41 55 41 54 55 53 44 89 d3 09 cb 48 83 ec 38 48 8b 05 c5 03 29 01 <4c> 8b 20 4c 39 e0 0f 84 d7 01 00 00 4c 89 44 24 08 89 54 24 20 [ 2.613080] RIP: ima_match_policy+0x23/0x390 RSP: ffffc90000193e88 [ 2.613080] CR2: 0000000000000000 [ 2.613080] ---[ end trace 9a9f0a8a73079f6a ]--- [ 2.673052] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 [ 2.673052] [ 2.675337] Kernel Offset: disabled [ 2.676405] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 Signed-off-by: Petr Vorel Signed-off-by: Mimi Zohar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

iversion: Rename make inode_cmp_iversion{+raw} to inode_eq_iversion{+raw}

2018-02-01T13:15:25+00:00

The function inode_cmp_iversion{+raw} is counter-intuitive, because it returns true when the counters are different and false when these are equal. Rename it to inode_eq_iversion{+raw}, which will returns true when the counters are equal and false otherwise. Signed-off-by: Goffredo Baroncelli Signed-off-by: Jeff Layton

Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

2018-01-31T21:07:35+00:00

Pull integrity updates from James Morris: "This contains a mixture of bug fixes, code cleanup, and new functionality. Of note is the integrity cache locking fix, file change detection, and support for a new EVM portable and immutable signature type. The re-introduction of the integrity cache lock (iint) fixes the problem of attempting to take the i_rwsem shared a second time, when it was previously taken exclusively. Defining atomic flags resolves the original iint/i_rwsem circular locking - accessing the file data vs. modifying the file metadata. Although it fixes the O_DIRECT problem as well, a subsequent patch is needed to remove the explicit O_DIRECT prevention. For performance reasons, detecting when a file has changed and needs to be re-measured, re-appraised, and/or re-audited, was limited to after the last writer has closed, and only if the file data has changed. Detecting file change is based on i_version. For filesystems that do not support i_version, remote filesystems, or userspace filesystems, the file was measured, appraised and/or audited once and never re-evaluated. Now local filesystems, which do not support i_version or are not mounted with the i_version option, assume the file has changed and are required to re-evaluate the file. This change does not address detecting file change on remote or userspace filesystems. Unlike file data signatures, which can be included and distributed in software packages (eg. rpm, deb), the existing EVM signature, which protects the file metadata, could not be included in software packages, as it includes file system specific information (eg. i_ino, possibly the UUID). This pull request defines a new EVM portable and immutable file metadata signature format, which can be included in software packages" * 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: ima/policy: fix parsing of fsuuid ima: Use i_version only when filesystem supports it integrity: remove unneeded initializations in integrity_iint_cache entries ima: log message to module appraisal error ima: pass filename to ima_rdwr_violation_check() ima: Fix line continuation format ima: support new "hash" and "dont_hash" policy actions ima: re-introduce own integrity cache lock EVM: Add support for portable signature format EVM: Allow userland to permit modification of EVM-protected metadata ima: relax requiring a file signature for new files with zero length

IMA: switch IMA over to new i_version API

2018-01-29T11:42:21+00:00

Signed-off-by: Jeff Layton

ima: Use i_version only when filesystem supports it

2017-12-18T14:43:49+00:00

i_version is only supported by a filesystem when the SB_I_VERSION flag is set. This patch tests for the SB_I_VERSION flag before using i_version. If we can't use i_version to detect a file change then we must assume the file has changed in the last_writer path and remeasure it. On filesystems without i_version support IMA used to measure a file only once and didn't detect any changes to a file. With this patch IMA now works properly on these filesystems. Signed-off-by: Sascha Hauer Reviewed-by: Jeff Layton Signed-off-by: Mimi Zohar

ima: log message to module appraisal error

2017-12-18T14:43:48+00:00

Simple but useful message log to the user in case of module appraise is forced and fails due to the lack of file descriptor, that might be caused by kmod calls to compressed modules. Signed-off-by: Bruno E. O. Meneguele Signed-off-by: Mimi Zohar

ima: pass filename to ima_rdwr_violation_check()

2017-12-18T14:43:48+00:00

ima_rdwr_violation_check() retrieves the full path of a measured file by calling ima_d_path(). If process_measurement() calls this function, it reuses the pointer and passes it to the functions to measure/appraise/audit an accessed file. After commit bc15ed663e7e ("ima: fix ima_d_path() possible race with rename"), ima_d_path() first tries to retrieve the full path by calling d_absolute_path() and, if there is an error, copies the dentry name to the buffer passed as argument. However, ima_rdwr_violation_check() passes to ima_d_path() the pointer of a local variable. process_measurement() might be reusing the pointer to an area in the stack which may have been already overwritten after ima_rdwr_violation_check() returned. Correct this issue by passing to ima_rdwr_violation_check() the pointer of a buffer declared in process_measurement(). Fixes: bc15ed663e7e ("ima: fix ima_d_path() possible race with rename") Signed-off-by: Roberto Sassu Signed-off-by: Mimi Zohar

ima: support new "hash" and "dont_hash" policy actions

2017-12-18T14:43:38+00:00

The builtin ima_appraise_tcb policy, which is specified on the boot command line, can be replaced with a custom policy, normally early in the boot process. Custom policies can be more restrictive in some ways, like requiring file signatures, but can be less restrictive in other ways, like not appraising mutable files. With a less restrictive policy in place, files in the builtin policy might not be hashed and labeled with a security.ima hash. On reboot, files which should be labeled in the ima_appraise_tcb are not labeled, possibly preventing the system from booting properly. To resolve this problem, this patch extends the existing IMA policy actions "measure", "dont_measure", "appraise", "dont_appraise", and "audit" with "hash" and "dont_hash". The new "hash" action will write the file hash as security.ima, but without requiring the file to be appraised as well. For example, the builtin ima_appraise_tcb policy includes the rule, "appraise fowner=0". Adding the "hash fowner=0" rule to a custom policy, will cause the needed file hashes to be calculated and written as security.ima xattrs. Signed-off-by: Mimi Zohar Signed-off-by: Stefan Berger

ima: Use i_version only when filesystem supports it

2017-12-13T12:23:02+00:00

ima: re-introduce own integrity cache lock

2017-12-11T22:20:47+00:00

Before IMA appraisal was introduced, IMA was using own integrity cache lock along with i_mutex. process_measurement and ima_file_free took the iint->mutex first and then the i_mutex, while setxattr, chmod and chown took the locks in reverse order. To resolve the potential deadlock, i_mutex was moved to protect entire IMA functionality and the redundant iint->mutex was eliminated. Solution was based on the assumption that filesystem code does not take i_mutex further. But when file is opened with O_DIRECT flag, direct-io implementation takes i_mutex and produces deadlock. Furthermore, certain other filesystem operations, such as llseek, also take i_mutex. More recently some filesystems have replaced their filesystem specific lock with the global i_rwsem to read a file. As a result, when IMA attempts to calculate the file hash, reading the file attempts to take the i_rwsem again. To resolve O_DIRECT related deadlock problem, this patch re-introduces iint->mutex. But to eliminate the original chmod() related deadlock problem, this patch eliminates the requirement for chmod hooks to take the iint->mutex by introducing additional atomic iint->attr_flags to indicate calling of the hooks. The allowed locking order is to take the iint->mutex first and then the i_rwsem. Original flags were cleared in chmod(), setxattr() or removwxattr() hooks and tested when file was closed or opened again. New atomic flags are set or cleared in those hooks and tested to clear iint->flags on close or on open. Atomic flags are following: * IMA_CHANGE_ATTR - indicates that chATTR() was called (chmod, chown, chgrp) and file attributes have changed. On file open, it causes IMA to clear iint->flags to re-evaluate policy and perform IMA functions again. * IMA_CHANGE_XATTR - indicates that setxattr or removexattr was called and extended attributes have changed. On file open, it causes IMA to clear iint->flags IMA_DONE_MASK to re-appraise. * IMA_UPDATE_XATTR - indicates that security.ima needs to be updated. It is cleared if file policy changes and no update is needed. * IMA_DIGSIG - indicates that file security.ima has signature and file security.ima must not update to file has on file close. * IMA_MUST_MEASURE - indicates the file is in the measurement policy. Fixes: Commit 6552321831dc ("xfs: remove i_iolock and use i_rwsem in the VFS inode instead") Signed-off-by: Dmitry Kasatkin Signed-off-by: Mimi Zohar