kernel.git/security/integrity/ima/ima_main.c, branch linux-5.8.y

ima: Fix NULL pointer dereference in ima_file_hash

2020-10-29T09:07:38Z

[ Upstream commit aa662fc04f5b290b3979332588bf8d812b189962 ] ima_file_hash can be called when there is no iint->ima_hash available even though the inode exists in the integrity cache. It is fairly common for a file to not have a hash. (e.g. an mknodat, prior to the file being closed). Another example where this can happen (suggested by Jann Horn): Process A does: while(1) { unlink("/tmp/imafoo"); fd = open("/tmp/imafoo", O_RDWR|O_CREAT|O_TRUNC, 0700); if (fd == -1) { perror("open"); continue; } write(fd, "A", 1); close(fd); } and Process B does: while (1) { int fd = open("/tmp/imafoo", O_RDONLY); if (fd == -1) continue; char *mapping = mmap(NULL, 0x1000, PROT_READ|PROT_EXEC, MAP_PRIVATE, fd, 0); if (mapping != MAP_FAILED) munmap(mapping, 0x1000); close(fd); } Due to the race to get the iint->mutex between ima_file_hash and process_measurement iint->ima_hash could still be NULL. Fixes: 6beea7afcc72 ("ima: add the ability to query the cached hash of a given file") Signed-off-by: KP Singh Reviewed-by: Florent Revest Signed-off-by: Mimi Zohar Signed-off-by: Sasha Levin

ima: fix mprotect checking

2020-06-12T15:30:18Z

Make sure IMA is enabled before checking mprotect change. Addresses report of a 3.7% regression of boot-time.dhcp. Fixes: 8eb613c0b8f1 ("ima: verify mprotect change is consistent with mmap policy") Reported-by: kernel test robot Reviewed-by: Lakshmi Ramasubramanian Tested-by: Xing Zhengjun Signed-off-by: Mimi Zohar

ima: verify mprotect change is consistent with mmap policy

2020-05-22T18:41:04Z

Files can be mmap'ed read/write and later changed to execute to circumvent IMA's mmap appraise policy rules. Due to locking issues (mmap semaphore would be taken prior to i_mutex), files can not be measured or appraised at this point. Eliminate this integrity gap, by denying the mprotect PROT_EXECUTE change, if an mmap appraise policy rule exists. On mprotect change success, return 0. On failure, return -EACESS. Reviewed-by: Lakshmi Ramasubramanian Signed-off-by: Mimi Zohar

ima: Evaluate error in init_ima()

2020-04-20T02:03:39Z

Evaluate error in init_ima() before register_blocking_lsm_notifier() and return if not zero. Cc: stable@vger.kernel.org # 5.3.x Fixes: b16942455193 ("ima: use the lsm policy update notifier") Signed-off-by: Roberto Sassu Reviewed-by: James Morris Signed-off-by: Mimi Zohar

integrity: Remove duplicate pr_fmt definitions

2020-02-28T19:32:58Z

The #define for formatting log messages, pr_fmt, is duplicated in the files under security/integrity. This change moves the definition to security/integrity/integrity.h and removes the duplicate definitions in the other files under security/integrity. With this change, the messages in the following files will be prefixed with 'integrity'. security/integrity/platform_certs/platform_keyring.c security/integrity/platform_certs/load_powerpc.c security/integrity/platform_certs/load_uefi.c security/integrity/iint.c e.g. "integrity: Error adding keys to platform keyring %s\n" And the messages in the following file will be prefixed with 'ima'. security/integrity/ima/ima_mok.c e.g. "ima: Allocating IMA blacklist keyring.\n" For the rest of the files under security/integrity, there will be no change in the message format. Suggested-by: Shuah Khan Suggested-by: Joe Perches Signed-off-by: Tushar Sugandhi Reviewed-by: Lakshmi Ramasubramanian Signed-off-by: Mimi Zohar

IMA: Add log statements for failure conditions

2020-02-28T19:32:58Z

process_buffer_measurement() does not have log messages for failure conditions. This change adds a log statement in the above function. Suggested-by: Joe Perches Signed-off-by: Tushar Sugandhi Reviewed-by: Mimi Zohar Reviewed-by: Lakshmi Ramasubramanian Signed-off-by: Mimi Zohar

ima: add the ability to query the cached hash of a given file

2020-01-22T20:22:51Z

This allows other parts of the kernel (perhaps a stacked LSM allowing system monitoring, eg. the proposed KRSI LSM [1]) to retrieve the hash of a given file from IMA if it's present in the iint cache. It's true that the existence of the hash means that it's also in the audit logs or in /sys/kernel/security/ima/ascii_runtime_measurements, but it can be difficult to pull that information out for every subsequent exec. This is especially true if a given host has been up for a long time and the file was first measured a long time ago. It should be kept in mind that this function gives access to cached entries which can be removed, for instance on security_inode_free(). This is based on Peter Moody's patch: https://sourceforge.net/p/linux-ima/mailman/message/33036180/ [1] https://lkml.org/lkml/2019/9/10/393 Signed-off-by: Florent Revest Reviewed-by: KP Singh Signed-off-by: Mimi Zohar

IMA: Add support to limit measuring keys

2019-12-12T13:53:50Z

Limit measuring keys to those keys being loaded onto a given set of keyrings only and when the user id (uid) matches if uid is specified in the policy. This patch defines a new IMA policy option namely "keyrings=" that can be used to specify a set of keyrings. If this option is specified in the policy for "measure func=KEY_CHECK" then only the keys loaded onto a keyring given in the "keyrings=" option are measured. If uid is specified in the policy then the key is measured only if the current user id matches the one specified in the policy. Added a new parameter namely "keyring" (name of the keyring) to process_buffer_measurement(). The keyring name is passed to ima_get_action() to determine the required action. ima_match_rules() is updated to check keyring in the policy, if specified, for KEY_CHECK function. Signed-off-by: Lakshmi Ramasubramanian Signed-off-by: Mimi Zohar

IMA: Check IMA policy flag

2019-12-12T13:53:50Z

process_buffer_measurement() may be called prior to IMA being initialized (for instance, when the IMA hook is called when a key is added to the .builtin_trusted_keys keyring), which would result in a kernel panic. This patch adds the check in process_buffer_measurement() to return immediately if IMA is not initialized yet. Signed-off-by: Lakshmi Ramasubramanian Signed-off-by: Mimi Zohar

ima: Check against blacklisted hashes for files with modsig

2019-11-12T01:25:50Z

Asymmetric private keys are used to sign multiple files. The kernel currently supports checking against blacklisted keys. However, if the public key is blacklisted, any file signed by the blacklisted key will automatically fail signature verification. Blacklisting the public key is not fine enough granularity, as we might want to only blacklist a particular file. This patch adds support for checking against the blacklisted hash of the file, without the appended signature, based on the IMA policy. It defines a new policy option "appraise_flag=check_blacklist". In addition to the blacklisted binary hashes stored in the firmware "dbx" variable, the Linux kernel may be configured to load blacklisted binary hashes onto the .blacklist keyring as well. The following example shows how to blacklist a specific kernel module hash. $ sha256sum kernel/kheaders.ko 77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 kernel/kheaders.ko $ grep BLACKLIST .config CONFIG_SYSTEM_BLACKLIST_KEYRING=y CONFIG_SYSTEM_BLACKLIST_HASH_LIST="blacklist-hash-list" $ cat certs/blacklist-hash-list "bin:77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3" Update the IMA custom measurement and appraisal policy rules (/etc/ima-policy): measure func=MODULE_CHECK template=ima-modsig appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig After building, installing, and rebooting the kernel: 545660333 ---lswrv 0 0 \_ blacklist: bin:77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 measure func=MODULE_CHECK template=ima-modsig appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig modprobe: ERROR: could not insert 'kheaders': Permission denied 10 0c9834db5a0182c1fb0cdc5d3adcf11a11fd83dd ima-sig sha256:3bc6ed4f0b4d6e31bc1dbc9ef844605abc7afdc6d81a57d77a1ec9407997c40 2 /usr/lib/modules/5.4.0-rc3+/kernel/kernel/kheaders.ko 10 82aad2bcc3fa8ed94762356b5c14838f3bcfa6a0 ima-modsig sha256:3bc6ed4f0b4d6e31bc1dbc9ef844605abc7afdc6d81a57d77a1ec9407997c40 2 /usr/lib/modules/5.4.0rc3+/kernel/kernel/kheaders.ko sha256:77fa889b3 5a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 3082029a06092a864886f70d010702a082028b30820287020101310d300b0609608648 016503040201300b06092a864886f70d01070131820264.... 10 25b72217cc1152b44b134ce2cd68f12dfb71acb3 ima-buf sha256:8b58427fedcf8f4b20bc8dc007f2e232bf7285d7b93a66476321f9c2a3aa132 b blacklisted-hash 77fa889b35a05338ec52e51591c1b89d4c8d1c99a21251d7c22b1a8642a6bad3 Signed-off-by: Nayna Jain [zohar@linux.ibm.com: updated patch description] Signed-off-by: Mimi Zohar Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/1572492694-6520-8-git-send-email-zohar@linux.ibm.com