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meta-integrity/README.md: update

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Signed-off-by: Lans Zhang <jia.zhang@windriver.com>
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Lans Zhang
2017-08-15 09:56:49 +08:00
parent 09f1239567
commit 2c265a6fc3
1 changed files with 45 additions and 37 deletions
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@@ -22,40 +22,9 @@ files and applications to be loaded if the hashes match (and will save the
updated hash if the file is modified) but refuse to load it if it doesn't. This
provides some protection against offline tampering of the files.
NOTE: Extended file system attribute is required for IMA appraisal, but not
all file systems can support it. Typically, the pseudo file systems, such as
sysfs, proc, tmpfs and ramfs, certain disk-based file systems, such as FAT,
and network file systems, such as NFS, don't support extended attribute,
meaning IMA appraisal is not available with them.
By default, the following constraint conditions are applied by design of this
layer:
##### Dependency
- meta-tpm
This layer provides the kernel configurations for TPM 1.x enablement.
- meta-tpm2
This layer provides the kernel configurations for TPM 2.0 enablement.
##### Use The External IMA Policy
initramfs is a good place to run some IMA initializations, such as loading
the IMA policy, as well as the public keys used to verify IMA signatures.
###### The default external IMA policy
The default external IMA policy enforces appraising all the executable, shared
library, kernel modules and firmwares with the digital signature in the
effective root identity (euid=0). Hence, the opportunity of loading the default
external IMA policy occurs at the end of initramfs initializations, just before
switch_root.
Instead of running switch_root directly from initramfs, a statically linked
switch_root from the real rootfs is called and it must be already signed
properly. Otherwise, switch_root will fail to mount the real rootfs and kernel
panic will happen due to this failure.
The default external IMA policy is located at `/etc/ima_policy.default` in
initramfs. If a custom external IMA policy file exists, the default external
IMA policy file won't be used any more.
The default external IMA policy enables the following constraint conditions:
- Appraise the files for exec'd (the executables), files mmap'd for exec
(shared libraries), kernel modules and firmwares in effective root identity
(euid=0).
@@ -71,10 +40,49 @@ The default external IMA policy enables the following constraint conditions:
modules and firmwares.
- Allow to run the updated executables, shared libraries, kernel modules and
firmwares during RPM installation.
- Note the different behaviors when executing a script.
e.g, launching a python script with "./test.py" is allowed only when test.py
is signed, and launching a python script with "python test.py" is always
allowed as long as the python interpreter is signed.
- Enforce the subsequent policy file write to be verified by a trusted IMA
certificate.
NOTE:
- The different behaviors when executing a script, e.g, launching a python
script with "./test.py" is allowed only when test.py is signed, and launching
a python script with "python test.py" is always allowed as long as the python
interpreter is signed.
- Extended file system attribute is required for IMA appraisal, but not
all file systems can support it. Typically, the pseudo file systems, such as
sysfs, proc, tmpfs and ramfs, certain disk-based file systems, such as FAT,
and network file systems, such as NFS, don't support extended attribute,
meaning IMA appraisal is not available with them.
##### Dependency
- meta-tpm
This layer provides the kernel configurations and TSS for TPM 1.x enablement.
- meta-tpm2
This layer provides the kernel configurations and TSS for TPM 2.0 enablement.
##### Use The External IMA Policy
initramfs is a good place to run some IMA initializations, such as loading
the IMA policy, as well as the trusted IMA certificate used to verify IMA
signatures.
###### The default external IMA policy
The default external IMA policy enforces appraising all the executable, shared
library, kernel modules and firmwares with the digital signature in the
effective root identity (euid=0). Hence, the opportunity of loading the default
external IMA policy occurs at the end of initramfs initializations, just before
switch_root.
Instead of running switch_root directly from initramfs, a statically linked
switch_root from the real rootfs is launched and it must be already signed
properly. Otherwise, switch_root will fail to mount the real rootfs and kernel
panic will happen due to this failure.
The default external IMA policy is located at `/etc/ima_policy.default` in
initramfs. If a custom external IMA policy file exists at `/etc/ima_policy`,
the default external IMA policy file won't be used. In addition, the IMA
policies signed by the trusted IMA certificate in the real rootfs is also
attempted to be loaded if any.
###### The custom external IMA policy
If the default external IMA policy cannot meet the protection requirement, it