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Message-ID: <c740a85c-fc0f-b2d7-d7bf-bcca278a94ae@linux.microsoft.com>
Date: Tue, 6 Jul 2021 12:24:57 -0700
From: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To: Roberto Sassu <roberto.sassu@...wei.com>, zohar@...ux.ibm.com,
paul@...l-moore.com
Cc: stephen.smalley.work@...il.com, prsriva02@...il.com,
tusharsu@...ux.microsoft.com, linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH v3 3/3] ima: Add digest and digest_len params to the
functions to measure a buffer
On 7/5/2021 2:09 AM, Roberto Sassu wrote:
> This patch adds the 'digest' and 'digest_len' parameters to
> ima_measure_critical_data() and process_buffer_measurement(), so that
> callers can get the digest of the passed buffer.
>
> These functions calculate the digest even if there is no suitable rule in
> the IMA policy and, in this case, they simply return 1 before generating a
> new measurement entry.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
> include/linux/ima.h | 5 +--
> security/integrity/ima/ima.h | 2 +-
> security/integrity/ima/ima_appraise.c | 2 +-
> security/integrity/ima/ima_asymmetric_keys.c | 2 +-
> security/integrity/ima/ima_init.c | 3 +-
> security/integrity/ima/ima_main.c | 36 ++++++++++++++------
> security/integrity/ima/ima_queue_keys.c | 2 +-
> security/selinux/ima.c | 6 ++--
> 8 files changed, 39 insertions(+), 19 deletions(-)
Reviewed-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
-lakshmi
>
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 60492263aa64..b6ab66a546ae 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -38,7 +38,7 @@ extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
> extern int ima_measure_critical_data(const char *event_label,
> const char *event_name,
> const void *buf, size_t buf_len,
> - bool hash);
> + bool hash, u8 *digest, size_t digest_len);
>
> #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
> extern void ima_appraise_parse_cmdline(void);
> @@ -147,7 +147,8 @@ static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {
> static inline int ima_measure_critical_data(const char *event_label,
> const char *event_name,
> const void *buf, size_t buf_len,
> - bool hash)
> + bool hash, u8 *digest,
> + size_t digest_len)
> {
> return -ENOENT;
> }
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 03db221324c3..2f4c20b16ad7 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -268,7 +268,7 @@ int process_buffer_measurement(struct user_namespace *mnt_userns,
> struct inode *inode, const void *buf, int size,
> const char *eventname, enum ima_hooks func,
> int pcr, const char *func_data,
> - bool buf_hash);
> + bool buf_hash, u8 *digest, size_t digest_len);
> void ima_audit_measurement(struct integrity_iint_cache *iint,
> const unsigned char *filename);
> int ima_alloc_init_template(struct ima_event_data *event_data,
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index ef9dcfce45d4..63bec42c353f 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -357,7 +357,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
> if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
> process_buffer_measurement(&init_user_ns, NULL, digest, digestsize,
> "blacklisted-hash", NONE,
> - pcr, NULL, false);
> + pcr, NULL, false, NULL, 0);
> }
>
> return rc;
> diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
> index c985418698a4..f6aa0b47a772 100644
> --- a/security/integrity/ima/ima_asymmetric_keys.c
> +++ b/security/integrity/ima/ima_asymmetric_keys.c
> @@ -62,5 +62,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
> */
> process_buffer_measurement(&init_user_ns, NULL, payload, payload_len,
> keyring->description, KEY_CHECK, 0,
> - keyring->description, false);
> + keyring->description, false, NULL, 0);
> }
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 5076a7d9d23e..b26fa67476b4 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -154,7 +154,8 @@ int __init ima_init(void)
> ima_init_key_queue();
>
> ima_measure_critical_data("kernel_info", "kernel_version",
> - UTS_RELEASE, strlen(UTS_RELEASE), false);
> + UTS_RELEASE, strlen(UTS_RELEASE), false,
> + NULL, 0);
>
> return rc;
> }
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index b512c06d8ee1..360266da5a10 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -838,17 +838,20 @@ int ima_post_load_data(char *buf, loff_t size,
> * @pcr: pcr to extend the measurement
> * @func_data: func specific data, may be NULL
> * @buf_hash: measure buffer data hash
> + * @digest: buffer digest will be written to
> + * @digest_len: buffer length
> *
> * Based on policy, either the buffer data or buffer data hash is measured
> *
> - * Return: 0 if the buffer has been successfully measured, a negative value
> - * otherwise.
> + * Return: 0 if the buffer has been successfully measured, 1 if the digest
> + * has been written to the passed location but not added to a measurement entry,
> + * a negative value otherwise.
> */
> int process_buffer_measurement(struct user_namespace *mnt_userns,
> struct inode *inode, const void *buf, int size,
> const char *eventname, enum ima_hooks func,
> int pcr, const char *func_data,
> - bool buf_hash)
> + bool buf_hash, u8 *digest, size_t digest_len)
> {
> int ret = 0;
> const char *audit_cause = "ENOMEM";
> @@ -869,7 +872,10 @@ int process_buffer_measurement(struct user_namespace *mnt_userns,
> int action = 0;
> u32 secid;
>
> - if (!ima_policy_flag)
> + if (digest && digest_len < digest_hash_len)
> + return -EINVAL;
> +
> + if (!ima_policy_flag && !digest)
> return -ENOENT;
>
> template = ima_template_desc_buf();
> @@ -891,7 +897,7 @@ int process_buffer_measurement(struct user_namespace *mnt_userns,
> action = ima_get_action(mnt_userns, inode, current_cred(),
> secid, 0, func, &pcr, &template,
> func_data);
> - if (!(action & IMA_MEASURE))
> + if (!(action & IMA_MEASURE) && !digest)
> return -ENOENT;
> }
>
> @@ -922,6 +928,12 @@ int process_buffer_measurement(struct user_namespace *mnt_userns,
> event_data.buf_len = digest_hash_len;
> }
>
> + if (digest)
> + memcpy(digest, iint.ima_hash->digest, digest_hash_len);
> +
> + if (!ima_policy_flag || (func && !(action & IMA_MEASURE)))
> + return 1;
> +
> ret = ima_alloc_init_template(&event_data, &entry, template);
> if (ret < 0) {
> audit_cause = "alloc_entry";
> @@ -964,7 +976,7 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
>
> process_buffer_measurement(file_mnt_user_ns(f.file), file_inode(f.file),
> buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
> - NULL, false);
> + NULL, false, NULL, 0);
> fdput(f);
> }
>
> @@ -975,26 +987,30 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
> * @buf: pointer to buffer data
> * @buf_len: length of buffer data (in bytes)
> * @hash: measure buffer data hash
> + * @digest: buffer digest will be written to
> + * @digest_len: buffer length
> *
> * Measure data critical to the integrity of the kernel into the IMA log
> * and extend the pcr. Examples of critical data could be various data
> * structures, policies, and states stored in kernel memory that can
> * impact the integrity of the system.
> *
> - * Return: 0 if the buffer has been successfully measured, a negative value
> - * otherwise.
> + * Return: 0 if the buffer has been successfully measured, 1 if the digest
> + * has been written to the passed location but not added to a measurement entry,
> + * a negative value otherwise.
> */
> int ima_measure_critical_data(const char *event_label,
> const char *event_name,
> const void *buf, size_t buf_len,
> - bool hash)
> + bool hash, u8 *digest, size_t digest_len)
> {
> if (!event_name || !event_label || !buf || !buf_len)
> return -ENOPARAM;
>
> return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len,
> event_name, CRITICAL_DATA, 0,
> - event_label, hash);
> + event_label, hash, digest,
> + digest_len);
> }
>
> static int __init init_ima(void)
> diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
> index 979ef6c71f3d..93056c03bf5a 100644
> --- a/security/integrity/ima/ima_queue_keys.c
> +++ b/security/integrity/ima/ima_queue_keys.c
> @@ -165,7 +165,7 @@ void ima_process_queued_keys(void)
> entry->keyring_name,
> KEY_CHECK, 0,
> entry->keyring_name,
> - false);
> + false, NULL, 0);
> list_del(&entry->list);
> ima_free_key_entry(entry);
> }
> diff --git a/security/selinux/ima.c b/security/selinux/ima.c
> index 34d421861bfc..727c4e43219d 100644
> --- a/security/selinux/ima.c
> +++ b/security/selinux/ima.c
> @@ -86,7 +86,8 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
> }
>
> ima_measure_critical_data("selinux", "selinux-state",
> - state_str, strlen(state_str), false);
> + state_str, strlen(state_str), false,
> + NULL, 0);
>
> kfree(state_str);
>
> @@ -103,7 +104,8 @@ void selinux_ima_measure_state_locked(struct selinux_state *state)
> }
>
> ima_measure_critical_data("selinux", "selinux-policy-hash",
> - policy, policy_len, true);
> + policy, policy_len, true,
> + NULL, 0);
>
> vfree(policy);
> }
>
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