[ Upstream commit 738c9738e690f5cea24a3ad6fd2d9a323cf614f6 ]

In ima_match_rules(), if ima_filter_rule_match() returns -ENOENT due to
the rule being NULL, the function incorrectly skips the 'if (!rc)' check
and sets 'result = true'. The LSM rule is considered a match, causing
extra files to be measured by IMA.

This issue can be reproduced in the following scenario:
After unloading the SELinux policy module via 'semodule -d', if an IMA
measurement is triggered before ima_lsm_rules is updated,
in ima_match_rules(), the first call to ima_filter_rule_match() returns
-ESTALE. This causes the code to enter the 'if (rc == -ESTALE &&
!rule_reinitialized)' block, perform ima_lsm_copy_rule() and retry. In
ima_lsm_copy_rule(), since the SELinux module has been removed, the rule
becomes NULL, and the second call to ima_filter_rule_match() returns
-ENOENT. This bypasses the 'if (!rc)' check and results in a false match.

Call trace:
  selinux_audit_rule_match+0x310/0x3b8
  security_audit_rule_match+0x60/0xa0
  ima_match_rules+0x2e4/0x4a0
  ima_match_policy+0x9c/0x1e8
  ima_get_action+0x48/0x60
  process_measurement+0xf8/0xa98
  ima_bprm_check+0x98/0xd8
  security_bprm_check+0x5c/0x78
  search_binary_handler+0x6c/0x318
  exec_binprm+0x58/0x1b8
  bprm_execve+0xb8/0x130
  do_execveat_common.isra.0+0x1a8/0x258
  __arm64_sys_execve+0x48/0x68
  invoke_syscall+0x50/0x128
  el0_svc_common.constprop.0+0xc8/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x44/0x200
  el0t_64_sync_handler+0x100/0x130
  el0t_64_sync+0x3c8/0x3d0

Fix this by changing 'if (!rc)' to 'if (rc <= 0)' to ensure that error
codes like -ENOENT do not bypass the check and accidentally result in a
successful match.

Fixes: 4af4662fa4a9d ("integrity: IMA policy")
Signed-off-by: Zhao Yipeng <zhaoyipeng5@huawei.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

[ Upstream commit 8f3fc4f3f8aa6e99266c69cc78bdaa58379e65fc ]

Since commit 56305aa9b6fa ("exec: Compute file based creds only once"), the
credentials to be applied to the process after execution are not calculated
anymore for each step of finding intermediate interpreters (including the
final binary), but only after the final binary to be executed without
interpreter has been found.

In particular, that means that the bprm_check_security LSM hook will not
see the updated cred->e[ug]id for the intermediate and for the final binary
to be executed, since the function doing this task has been moved from
prepare_binprm(), which calls the bprm_check_security hook, to
bprm_creds_from_file().

This breaks the IMA expectation for the CREDS_CHECK hook, introduced with
commit d906c10d8a31 ("IMA: Support using new creds in appraisal policy"),
which expects to evaluate "the credentials that will be committed when the
new process is started". This is clearly not the case for the CREDS_CHECK
IMA hook, which is attached to bprm_check_security.

This issue does not affect systems which load a policy with the BPRM_CHECK
hook with no other criteria, as is the case with the built-in "tcb" and/or
"appraise_tcb" IMA policies. The "tcb" built-in policy measures all
executions regardless of the new credentials, and the "appraise_tcb" policy
is written in terms of the file owner, rather than IMA hooks.

However, it does affect systems without a BPRM_CHECK policy rule or with a
BPRM_CHECK policy rule that does not include what CREDS_CHECK evaluates. As
an extreme example, taking a standalone rule like:

measure func=CREDS_CHECK euid=0

This will not measure for example sudo (because CREDS_CHECK still sees the
bprm->cred->euid set to the regular user UID), but only the subsequent
commands after the euid was applied to the children.

Make set[ug]id programs measured/appraised again by splitting
ima_bprm_check() in two separate hook implementations (CREDS_CHECK now
being implemented by ima_creds_check()), and by attaching CREDS_CHECK to
the bprm_creds_from_file LSM hook.

The limitation of this approach is that CREDS_CHECK will not be invoked
anymore for the intermediate interpreters, like it was before, but only for
the final binary. This limitation can be removed only by reverting commit
56305aa9b6fa ("exec: Compute file based creds only once").

Link: https://github.com/linux-integrity/linux/issues/3
Fixes: 56305aa9b6fa ("exec: Compute file based creds only once")
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jann Horn <jannh@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Currently when both IMA and EVM are in fix mode, the IMA signature will
be reset to IMA hash if a program first stores IMA signature in
security.ima and then writes/removes some other security xattr for the
file.

For example, on Fedora, after booting the kernel with "ima_appraise=fix
evm=fix ima_policy=appraise_tcb" and installing rpm-plugin-ima,
installing/reinstalling a package will not make good reference IMA
signature generated. Instead IMA hash is generated,

    # getfattr -m - -d -e hex /usr/bin/bash
    # file: usr/bin/bash
    security.ima=0x0404...

This happens because when setting security.selinux, the IMA_DIGSIG flag
that had been set early was cleared. As a result, IMA hash is generated
when the file is closed.

Similarly, IMA signature can be cleared on file close after removing
security xattr like security.evm or setting/removing ACL.

Prevent replacing the IMA file signature with a file hash, by preventing
the IMA_DIGSIG flag from being reset.

Here's a minimal C reproducer which sets security.selinux as the last
step which can also replaced by removing security.evm or setting ACL,

    #include <stdio.h>
    #include <sys/xattr.h>
    #include <fcntl.h>
    #include <unistd.h>
    #include <string.h>
    #include <stdlib.h>

    int main() {
        const char* file_path = "/usr/sbin/test_binary";
        const char* hex_string = "030204d33204490066306402304";
        int length = strlen(hex_string);
        char* ima_attr_value;
        int fd;

        fd = open(file_path, O_WRONLY|O_CREAT|O_EXCL, 0644);
        if (fd == -1) {
            perror("Error opening file");
            return 1;
        }

        ima_attr_value = (char*)malloc(length / 2 );
        for (int i = 0, j = 0; i < length; i += 2, j++) {
            sscanf(hex_string + i, "%2hhx", &ima_attr_value[j]);
        }

        if (fsetxattr(fd, "security.ima", ima_attr_value, length/2, 0) == -1) {
            perror("Error setting extended attribute");
            close(fd);
            return 1;
        }

        const char* selinux_value= "system_u:object_r:bin_t:s0";
        if (fsetxattr(fd, "security.selinux", selinux_value, strlen(selinux_value), 0) == -1) {
            perror("Error setting extended attribute");
            close(fd);
            return 1;
        }

        close(fd);

        return 0;
    }

Signed-off-by: Coiby Xu <coxu@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Pull integrity update from Mimi Zohar:
 "A single commit to permit disabling IMA from the boot command line for
  just the kdump kernel.

  The exception itself sort of makes sense. My concern is that
  exceptions do not remain as exceptions, but somehow morph to become
  the norm"

* tag 'integrity-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity:
  ima: add a knob ima= to allow disabling IMA in kdump kernel

lookup_template_data_hash_algo() machinery is used to locate the
matching ima_algo_array[] element at read time; securityfs
allows to stash that into inode->i_private at object creation
time, so there's no need to bother

Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

removal of parent takes all children out

Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Kdump kernel doesn't need IMA functionality, and enabling IMA will cost
extra memory. It would be very helpful to allow IMA to be disabled for
kdump kernel.

Hence add a knob ima=on|off here to allow turning IMA off in kdump
kernel if needed.

Note that this IMA disabling is limited to kdump kernel, please don't
abuse it in other kernel and thus serious consequences are caused.

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Kdump kernel doesn't need IMA to do integrity measurement.
Hence the measurement list in 1st kernel doesn't need to be copied to
kdump kernel.

Here skip allocating buffer for measurement list copying if loading
kdump kernel. Then there won't be the later handling related to
ima_kexec_buffer.

Signed-off-by: Steven Chen <chenste@linux.microsoft.com>
Tested-by: Baoquan He <bhe@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

The amount of memory allocated at kexec load, even with the extra memory
allocated, might not be large enough for the entire measurement list.  The
indeterminate interval between kexec 'load' and 'execute' could exacerbate
this problem.

Define two new IMA events, 'kexec_load' and 'kexec_execute', to be
measured as critical data at kexec 'load' and 'execute' respectively.
Report the allocated kexec segment size, IMA binary log size and the
runtime measurements count as part of those events.

These events, and the values reported through them, serve as markers in
the IMA log to verify the IMA events are captured during kexec soft
reboot.  The presence of a 'kexec_load' event in between the last two
'boot_aggregate' events in the IMA log implies this is a kexec soft
reboot, and not a cold-boot. And the absence of 'kexec_execute' event
after kexec soft reboot implies missing events in that window which
results in inconsistency with TPM PCR quotes, necessitating a cold boot
for a successful remote attestation.

These critical data events are displayed as hex encoded ascii in the
ascii_runtime_measurement_list.  Verifying the critical data hash requires
calculating the hash of the decoded ascii string.

For example, to verify the 'kexec_load' data hash:

sudo cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements
| grep  kexec_load | cut -d' ' -f 6 | xxd -r -p | sha256sum

To verify the 'kexec_execute' data hash:

sudo cat /sys/kernel/security/integrity/ima/ascii_runtime_measurements
| grep kexec_execute | cut -d' ' -f 6 | xxd -r -p | sha256sum

Co-developed-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Steven Chen <chenste@linux.microsoft.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com> # ppc64/kvm
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

The extra memory allocated for carrying the IMA measurement list across
kexec is hard-coded as half a PAGE.  Make it configurable.

Define a Kconfig option, IMA_KEXEC_EXTRA_MEMORY_KB, to configure the
extra memory (in kb) to be allocated for IMA measurements added during
kexec soft reboot.  Ensure the default value of the option is set such
that extra half a page of memory for additional measurements is allocated
for the additional measurements.

Update ima_add_kexec_buffer() function to allocate memory based on the
Kconfig option value, rather than the currently hard-coded one.

Suggested-by: Stefan Berger <stefanb@linux.ibm.com>
Co-developed-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Steven Chen <chenste@linux.microsoft.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com> # ppc64/kvm
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>