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Message-Id: <1520615358.3911.1.camel@linux.vnet.ibm.com>
Date: Fri, 09 Mar 2018 12:09:18 -0500
From: Mimi Zohar <zohar@...ux.vnet.ibm.com>
To: Nayna Jain <nayna@...ux.vnet.ibm.com>, dhowells@...hat.com
Cc: keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org
Subject: Re: [PATCH v2 3/3] ima: support platform keyring for kernel
appraisal
On Fri, 2018-03-09 at 21:08 +0530, Nayna Jain wrote:
> Distros may sign the kernel images and, possibly, the initramfs with
> platform trusted keys. On secure boot enabled systems or embedded devices,
> these signatures are to be validated using keys on the platform keyring.
>
> This patch enables IMA-appraisal to access the platform keyring, based on a
> new Kconfig option "IMA_USE_PLATFORM_KEYRING".
>
> Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
Thanks, Nayna!
Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
> ---
> Changelog:
>
> v2:
> * Rename integrity_load_keyring() to integrity_find_keyring()
> * Fix the patch description per line length as suggested by Mimi
>
> security/integrity/digsig.c | 15 +++++++++++++++
> security/integrity/ima/Kconfig | 10 ++++++++++
> security/integrity/ima/ima_appraise.c | 22 +++++++++++++++++-----
> security/integrity/ima/ima_init.c | 4 ++++
> security/integrity/integrity.h | 17 ++++++++++++++++-
> 5 files changed, 62 insertions(+), 6 deletions(-)
>
> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> index 6f9e4ce568cd..cfeb977bced9 100644
> --- a/security/integrity/digsig.c
> +++ b/security/integrity/digsig.c
> @@ -34,6 +34,8 @@ static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
> ".ima",
> #endif
> "_module",
> + ".platform_keys",
> +
> };
>
> #ifdef CONFIG_INTEGRITY_TRUSTED_KEYRING
> @@ -78,6 +80,19 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
> return -EOPNOTSUPP;
> }
>
> +#ifdef CONFIG_IMA_USE_PLATFORM_KEYRING
> +int __init integrity_find_keyring(const unsigned int id)
> +{
> +
> + keyring[id] = find_keyring_by_name(keyring_name[id], 0);
> + if (IS_ERR(keyring[id]))
> + if (PTR_ERR(keyring[id]) != -ENOKEY)
> + return PTR_ERR(keyring[id]);
> + return 0;
> +
> +}
> +#endif
> +
> int __init integrity_init_keyring(const unsigned int id)
> {
> const struct cred *cred = current_cred();
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 35ef69312811..2e89d4f8a364 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -227,3 +227,13 @@ config IMA_APPRAISE_SIGNED_INIT
> default n
> help
> This option requires user-space init to be signed.
> +
> +config IMA_USE_PLATFORM_KEYRING
> + bool "IMA uses keys from Platform Keyring for verification"
> + depends on PLATFORM_KEYRING
> + depends on IMA_APPRAISE
> + depends on INTEGRITY_ASYMMETRIC_KEYS
> + default n
> + help
> + This option enables IMA appraisal to look for the platform
> + trusted keys in .platform_keys keyring.
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index f2803a40ff82..5fec29f40595 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -276,13 +276,25 @@ int ima_appraise_measurement(enum ima_hooks func,
> (const char *)xattr_value, rc,
> iint->ima_hash->digest,
> iint->ima_hash->length);
> - if (rc == -EOPNOTSUPP) {
> - status = INTEGRITY_UNKNOWN;
> - } else if (rc) {
> + if (rc) {
> + if (rc == -EOPNOTSUPP) {
> + status = INTEGRITY_UNKNOWN;
> + break;
> + }
> + if (func == KEXEC_KERNEL_CHECK) {
> + rc = integrity_digsig_verify(
> + INTEGRITY_KEYRING_PLATFORM,
> + (const char *)xattr_value,
> + xattr_len,
> + iint->ima_hash->digest,
> + iint->ima_hash->length);
> + if (!rc) {
> + status = INTEGRITY_PASS;
> + break;
> + }
> + }
> cause = "invalid-signature";
> status = INTEGRITY_FAIL;
> - } else {
> - status = INTEGRITY_PASS;
> }
> break;
> default:
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 29b72cd2502e..5778647c6bc4 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -122,6 +122,10 @@ int __init ima_init(void)
> if (rc)
> return rc;
>
> + rc = integrity_find_keyring(INTEGRITY_KEYRING_PLATFORM);
> + if (rc)
> + pr_info("Platform keyring is not found. (rc=%d)\n", rc);
> +
> rc = ima_init_crypto();
> if (rc)
> return rc;
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 50a8e3365df7..3d3b7171ead2 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -136,13 +136,23 @@ int integrity_kernel_read(struct file *file, loff_t offset,
> #define INTEGRITY_KEYRING_EVM 0
> #define INTEGRITY_KEYRING_IMA 1
> #define INTEGRITY_KEYRING_MODULE 2
> -#define INTEGRITY_KEYRING_MAX 3
> +#define INTEGRITY_KEYRING_PLATFORM 3
> +#define INTEGRITY_KEYRING_MAX 4
>
> #ifdef CONFIG_INTEGRITY_SIGNATURE
>
> int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
> const char *digest, int digestlen);
>
> +#ifdef CONFIG_IMA_USE_PLATFORM_KEYRING
> +int __init integrity_find_keyring(const unsigned int id);
> +#else
> +static inline int __init integrity_find_keyring(const unsigned int id)
> +{
> + return 0;
> +}
> +#endif
> +
> int __init integrity_init_keyring(const unsigned int id);
> int __init integrity_load_x509(const unsigned int id, const char *path);
> #else
> @@ -154,6 +164,11 @@ static inline int integrity_digsig_verify(const unsigned int id,
> return -EOPNOTSUPP;
> }
>
> +static inline int __init integrity_find_keyring(const unsigned int id)
> +{
> + return 0;
> +}
> +
> static inline int integrity_init_keyring(const unsigned int id)
> {
> return 0;
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