Re: [PATCH] ima: debugging late_initcall_sync measurements

[Yeoreum Yun <yeoreum.yun@arm.com>]

Hi Mimi,

Thanks to share the testing code and please see the below:

> With this "[RFC PATCH v3 0/4] Fix IMA + TPM initialisation ordering
> issue" patch set, how many records would be missing if IMA
> initialization is deferred to late_initcall_sync [1]?
>
> [1]https://lore.kernel.org/linux-integrity/cover.1777036497.git.noodles@meta.com/
> ---
> Jonathan, Yeoreum, others -
>
> By going into TPM-bypass mode, we can see how many measurements are actually
> missing when deferring IMA initialization to late_initcall_sync. As this is
> system/TPM dependent, I'd appreciate your checking. Please use the boot command
> line option "ima_policy=tcb|critical_data".
>
> thanks, Mimi
>
>  security/integrity/ima/ima.h      |  1 +
>  security/integrity/ima/ima_init.c |  6 ++++++
>  security/integrity/ima/ima_main.c | 19 +++++++++++++++++++
>  3 files changed, 26 insertions(+)
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 01aae19ed365..9a1117112fb2 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -286,6 +286,7 @@ extern bool ima_canonical_fmt;
>
>  /* Internal IMA function definitions */
>  int ima_init_core(bool late);
> +int ima_init_debug(bool late);
>  int ima_fs_init(void);
>  int ima_add_template_entry(struct ima_template_entry *entry, int violation,
>  			   const char *op, struct inode *inode,
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 5f335834a9bb..edd063b99685 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -122,6 +122,12 @@ void __init ima_load_x509(void)
>  }
>  #endif
>
> +int __init ima_init_debug(bool late)
> +{
> +	ima_add_boot_aggregate(late); /* just add an additional record */
> +	return 0;
> +}
> +
>  int __init ima_init_core(bool late)
>  {
>  	int rc;
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 42099bfe7e43..23e669be54fc 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -1254,6 +1254,7 @@ static int ima_kernel_module_request(char *kmod_name)
>
>  #endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
>
> +#define TESTING 1
>  static int __init init_ima(bool late)
>  {
>  	int error;
> @@ -1264,6 +1265,23 @@ static int __init init_ima(bool late)
>  		return 0;
>  	}
>
> +#ifdef TESTING
> +	/*
> +	 * Initialize early, even if it means going into TPM-bypass mode,
> +	 * but add an additional boot_aggregrate message for the
> +	 * late_initcall_sync.
> +	 *
> +	 * If measurement list records exist between the boot_aggregate
> +	 * and the boot_aggregate_late records, these records would be
> +	 * missing when IMA initializion is deferred to late_initcall_sync.
> +	 */
> +	if (ima_tpm_chip) {

I believe this should be:
  if (late) {
     ...
  }

> +		ima_init_debug(late); /* Add an additional record */
> +		return 0;
> +	}
> +
> +	ima_tpm_chip = tpm_default_chip();
> +#elif
>  	/*
>  	 * If we found the TPM during our first attempt, or we know there's no
>  	 * TPM, nothing further to do
> @@ -1276,6 +1294,7 @@ static int __init init_ima(bool late)
>  		pr_debug("TPM not available, will try later\n");
>  		return -EPROBE_DEFER;
>  	}
> +#endif
>
>  	if (!ima_tpm_chip)
>  		pr_info("No TPM chip found, activating TPM-bypass!\n");
> --
> 2.53.0

With above change I confirmed there is no meaurement log
between boot_aggregate and boot_aggregate_late except "kernel_version"
But this is ignorable since this UTS measurement is done in
"ima_init_core() (old: ima_init())" and it is part of ima initialisation.

1. ima_policy=tcb

  # cat /sys/kernel/security/ima/ascii_runtime_measurements
  10 0adefe762c149c7cec19da62f0da1297fcfbffff ima-ng sha256:0000000000000000000000000000000000000000000000000000000000000000 boot_aggregate
  10 4e5d73ebadfd8f850cb93ce4de755ba148a9a7d5 ima-ng sha256:0000000000000000000000000000000000000000000000000000000000000000 boot_aggregate_late
  10 7c23cc970eceec906f7a41bc2fbde770d7092209 ima-ng sha256:72ade6ae3d35cfe5ede7a77b1c0ed1d1782a899445fdcb219c0e994a084a70d5 /bin/busybox
  10 17ec669c65c401e5e85875cf2962eb7d8c47595f ima-ng sha256:dc6b013e9768d9b13bcd6678470448090138ca831f4771a43ce3988d8e54ffce /lib/ld-linux-aarch64.so.1
  10 58679a66ac1de17f02595625a8fbeafa259a4c81 ima-ng sha256:494f62bcfb2fcf1b427d5092fafa62c8df39a83b4a64402620b28846724f237f /usr/lib/libtirpc.so.3.0.0
  10 42f74ee200434576e33be153830b3d55bbe6d2bf ima-ng sha256:a18856b4f6927bc2b8dd4608c0768b8f98544a161b85bf4a64419131243ad300 /lib/libresolv.so.2
  10 626b4f7bd4f123d18d3a3d8719ed0ae19ee5f331 ima-ng sha256:b8d442de5d31c3f9d1bbb98785f04d4a23dc53442b286d85d4b355927cbe9af4 /lib/libc.so.6
  10 655a200869696207646377a58cab417fd35b09d2 ima-ng sha256:ad46146b6dd32b47213e5327f1bb2f962ef838a4b707ef7445fa2dbc9019b44f /etc/inittab
  10 81353202685e022fcd0069a3b2fc4eaa6b1db537 ima-ng sha256:74d698fe0a6862050af29083aa591c960ec1f67be960047e96bb6be5fc2bc0c0 /bin/mount
  10 ae64184ee607ef8f3aa08ab52cb548318534fd4b ima-ng sha256:27846b57e8234c6a9611b00351f581a54ad6f9a1920b9aa18ceb0ae28e4f7564 /lib/libmount.so.1.1.0
  10 5ea01f34e7705d1bdb936fd576e2aeb5fd78dab9 ima-ng sha256:3d2a414ec0355fcf0910224fb4a3c53e13d98731a35241edfdf4fb911ed9b210 /lib/libblkid.so.1.1.0
  10 22c48b4853594a08a73ad4ae6dbe6f2c2bebc6c5 ima-ng sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 /run/utmp
  10 3024ea5021f8a5d9fb4bd519d599bdca43b7fb93 ima-ng sha256:71ea9ffe2b30e5a9bdceff78785cf281cc41544474db8dc4605a06a597ce1edc /etc/fstab
  10 2e7530a0f56420991ac7611734cea4774b92b9ef ima-ng sha256:df4697d699442cfe73db7cc8b4c1b37e8a31e75e01f66a0d70134ac812fa683b /bin/mkdir
  10 3ad117a863aa1ed7b7c09e1d106f84abf7d2ae96 ima-ng sha256:c19a710989b43222431b02399273dba409fe10ca8eefff88eaa936fa695f8324 /bin/ln
  10 4141c82cb516ac3c846e0b08abcd6abeee7efa1a ima-ng sha256:b75d7f28772f71715a941c77e07e3922815391dd9cc5718ad21f2231c2da09bb /etc/hostname
  10 dfcedd3c7dc3ed42e09219804504489ab264e2e3 ima-ng sha256:dc1615df9f2012b20b81ffad8e07e16293039ba7fd897854ca3646d6cfea0c0f /etc/init.d/rcS
  ...

2. ima_policy=critical_data

  # cat /sys/kernel/security/ima/ascii_runtime_measurements
  10 0adefe762c149c7cec19da62f0da1297fcfbffff ima-ng sha256:0000000000000000000000000000000000000000000000000000000000000000 boot_aggregate
  10 49ab61dd97ea2f759edcb6c6a3387ac67f0aa576 ima-buf sha256:0c907aab3261194f16b0c2a422a82f145bc9b9ecb8fdb633fa43e3e5379f0af2 kernel_version 372e312e302d7263312b // Ignorable since it's generated by ima_init(_core)().
  10 4e5d73ebadfd8f850cb93ce4de755ba148a9a7d5 ima-ng sha256:0000000000000000000000000000000000000000000000000000000000000000 boot_aggregate_late

Therefore, init_ima() could move into late_initcall_sync like v1 did:
  - https://lore.kernel.org/all/20260417175759.3191279-2-yeoreum.yun@arm.com/

Thanks.

--
Sincerely,
Yeoreum Yun