linux/security/integrity, branch v5.14

evm: Check xattr size discrepancy between kernel and user

2021-06-21T12:34:21Z

The kernel and the user obtain an xattr value in two different ways: kernel (EVM): uses vfs_getxattr_alloc() which obtains the xattr value from the filesystem handler (raw value); user (ima-evm-utils): uses vfs_getxattr() which obtains the xattr value from the LSMs (normalized value). Normally, this does not have an impact unless security.selinux is set with setfattr, with a value not terminated by '\0' (this is not the recommended way, security.selinux should be set with the appropriate tools such as chcon and restorecon). In this case, the kernel and the user see two different xattr values: the former sees the xattr value without '\0' (raw value), the latter sees the value with '\0' (value normalized by SELinux). This could result in two different verification outcomes from EVM and ima-evm-utils, if a signature was calculated with a security.selinux value terminated by '\0' and the value set in the filesystem is not terminated by '\0'. The former would report verification failure due to the missing '\0', while the latter would report verification success (because it gets the normalized value with '\0'). This patch mitigates this issue by comparing in evm_calc_hmac_or_hash() the size of the xattr returned by the two xattr functions and by warning the user if there is a discrepancy. Signed-off-by: Roberto Sassu Suggested-by: Mimi Zohar Signed-off-by: Mimi Zohar

evm: output EVM digest calculation info

2021-06-20T15:10:25Z

Output the data used in calculating the EVM digest and the resulting digest as ascii hexadecimal strings. Suggested-by: Lakshmi Ramasubramanian (CONFIG_DYNAMIC_DEBUG) Reviewed-by: Lakshmi Ramasubramanian Reported-by: kernel test robot (Use %zu for size_t) Signed-off-by: Mimi Zohar

IMA: support for duplicate measurement records

2021-06-11T16:54:13Z

IMA measures contents of a given file/buffer/critical-data record, and properly re-measures it on change. However, IMA does not measure the duplicate value for a given record, since TPM extend is a very expensive operation. For example, if the record changes from value 'v#1' to 'v#2', and then back to 'v#1', IMA will not measure and log the last change to 'v#1', since the hash of 'v#1' for that record is already present in the IMA htable. This limits the ability of an external attestation service to accurately determine the current state of the system. The service would incorrectly conclude that the latest value of the given record on the system is 'v#2', and act accordingly. Define and use a new Kconfig option IMA_DISABLE_HTABLE to permit duplicate records in the IMA measurement list. In addition to the duplicate measurement records described above, other duplicate file measurement records may be included in the log, when CONFIG_IMA_DISABLE_HTABLE is enabled. For example, - i_version is not enabled, - i_generation changed, - same file present on different filesystems, - an inode is evicted from dcache Signed-off-by: Tushar Sugandhi Reviewed-by: Petr Vorel [zohar@linux.ibm.com: updated list of duplicate measurement records] Signed-off-by: Mimi Zohar

ima: Fix warning: no previous prototype for function 'ima_add_kexec_buffer'

2021-06-11T15:27:03Z

The function prototype for ima_add_kexec_buffer() is present in 'linux/ima.h'. But this header file is not included in ima_kexec.c where the function is implemented. This results in the following compiler warning when "-Wmissing-prototypes" flag is turned on: security/integrity/ima/ima_kexec.c:81:6: warning: no previous prototype for function 'ima_add_kexec_buffer' [-Wmissing-prototypes] Include the header file 'linux/ima.h' in ima_kexec.c to fix the compiler warning. Fixes: dce92f6b11c3 (arm64: Enable passing IMA log to next kernel on kexec) Reported-by: kernel test robot Signed-off-by: Lakshmi Ramasubramanian Acked-by: Rob Herring Signed-off-by: Mimi Zohar

ima: differentiate between EVM failures in the audit log

2021-06-10T20:36:41Z

Differentiate between an invalid EVM portable signature failure from other EVM HMAC/signature failures. Reviewed-by: Roberto Sassu Signed-off-by: Mimi Zohar

ima: Fix fall-through warning for Clang

2021-06-09T03:33:48Z

In preparation to enable -Wimplicit-fallthrough for Clang, fix a fall-through warning by explicitly adding a break statement instead of just letting the code fall through to the next case. Link: https://github.com/KSPP/linux/issues/115 Signed-off-by: Gustavo A. R. Silva Reviewed-by: Kees Cook Signed-off-by: Mimi Zohar

ima: Pass NULL instead of 0 to ima_get_action() in ima_file_mprotect()

2021-06-08T20:29:10Z

This patch fixes the sparse warning: sparse: warning: Using plain integer as NULL pointer Signed-off-by: Roberto Sassu Signed-off-by: Mimi Zohar

ima: Include header defining ima_post_key_create_or_update()

2021-06-08T20:29:10Z

This patch fixes the sparse warning for ima_post_key_create_or_update() by adding the header file that defines the prototype (linux/ima.h). Signed-off-by: Roberto Sassu Signed-off-by: Mimi Zohar

ima/evm: Fix type mismatch

2021-06-08T20:29:10Z

The endianness of a variable written to the measurement list cannot be determined at compile time, as it depends on the value of the ima_canonical_fmt global variable (set through a kernel option with the same name if the machine is big endian). If ima_canonical_fmt is false, the endianness of a variable is the same as the machine; if ima_canonical_fmt is true, the endianness is little endian. The warning arises due to this type of instruction: var = cpu_to_leXX(var) which tries to assign a value in little endian to a variable with native endianness (little or big endian). Given that the variables set with this instruction are not used in any operation but just written to a buffer, it is safe to force the type of the value being set to be the same of the type of the variable with: var = (__force )cpu_to_leXX(var) Reported-by: kernel test robot Signed-off-by: Roberto Sassu Signed-off-by: Mimi Zohar

ima: Set correct casting types

2021-06-08T20:29:10Z

The code expects that the values being parsed from a buffer when the ima_canonical_fmt global variable is true are in little endian. Thus, this patch sets the casting types accordingly. Reported-by: kernel test robot Signed-off-by: Roberto Sassu Signed-off-by: Mimi Zohar