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    Subject[PATCH v2 11/11] ima: Support additional conditionals in the KEXEC_CMDLINE hook function
    Date
    Take the properties of the kexec kernel's inode and the current task
    ownership into consideration when matching a KEXEC_CMDLINE operation to
    the rules in the IMA policy. This allows for some uniformity when
    writing IMA policy rules for KEXEC_KERNEL_CHECK, KEXEC_INITRAMFS_CHECK,
    and KEXEC_CMDLINE operations.

    Prior to this patch, it was not possible to write a set of rules like
    this:

    dont_measure func=KEXEC_KERNEL_CHECK obj_type=foo_t
    dont_measure func=KEXEC_INITRAMFS_CHECK obj_type=foo_t
    dont_measure func=KEXEC_CMDLINE obj_type=foo_t
    measure func=KEXEC_KERNEL_CHECK
    measure func=KEXEC_INITRAMFS_CHECK
    measure func=KEXEC_CMDLINE

    The inode information associated with the kernel being loaded by a
    kexec_kernel_load(2) syscall can now be included in the decision to
    measure or not

    Additonally, the uid, euid, and subj_* conditionals can also now be
    used in KEXEC_CMDLINE rules. There was no technical reason as to why
    those conditionals weren't being considered previously other than
    ima_match_rules() didn't have a valid inode to use so it immediately
    bailed out for KEXEC_CMDLINE operations rather than going through the
    full list of conditional comparisons.

    Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
    Cc: Eric Biederman <ebiederm@xmission.com>
    Cc: kexec@lists.infradead.org
    ---

    * v2
    - Moved the inode parameter of process_buffer_measurement() to be the
    first parameter so that it more closely matches process_masurement()

    include/linux/ima.h | 4 ++--
    kernel/kexec_file.c | 2 +-
    security/integrity/ima/ima.h | 2 +-
    security/integrity/ima/ima_api.c | 2 +-
    security/integrity/ima/ima_appraise.c | 2 +-
    security/integrity/ima/ima_asymmetric_keys.c | 2 +-
    security/integrity/ima/ima_main.c | 23 +++++++++++++++-----
    security/integrity/ima/ima_policy.c | 17 +++++----------
    security/integrity/ima/ima_queue_keys.c | 2 +-
    9 files changed, 31 insertions(+), 25 deletions(-)

    diff --git a/include/linux/ima.h b/include/linux/ima.h
    index 9164e1534ec9..d15100de6cdd 100644
    --- a/include/linux/ima.h
    +++ b/include/linux/ima.h
    @@ -25,7 +25,7 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
    enum kernel_read_file_id id);
    extern void ima_post_path_mknod(struct dentry *dentry);
    extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
    -extern void ima_kexec_cmdline(const void *buf, int size);
    +extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);

    #ifdef CONFIG_IMA_KEXEC
    extern void ima_add_kexec_buffer(struct kimage *image);
    @@ -103,7 +103,7 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
    return -EOPNOTSUPP;
    }

    -static inline void ima_kexec_cmdline(const void *buf, int size) {}
    +static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
    #endif /* CONFIG_IMA */

    #ifndef CONFIG_IMA_KEXEC
    diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
    index bb05fd52de85..07df431c1f21 100644
    --- a/kernel/kexec_file.c
    +++ b/kernel/kexec_file.c
    @@ -287,7 +287,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
    goto out;
    }

    - ima_kexec_cmdline(image->cmdline_buf,
    + ima_kexec_cmdline(kernel_fd, image->cmdline_buf,
    image->cmdline_buf_len - 1);
    }

    diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
    index 59ec28f5c117..ff2bf57ff0c7 100644
    --- a/security/integrity/ima/ima.h
    +++ b/security/integrity/ima/ima.h
    @@ -265,7 +265,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
    struct evm_ima_xattr_data *xattr_value,
    int xattr_len, const struct modsig *modsig, int pcr,
    struct ima_template_desc *template_desc);
    -void process_buffer_measurement(const void *buf, int size,
    +void process_buffer_measurement(struct inode *inode, const void *buf, int size,
    const char *eventname, enum ima_hooks func,
    int pcr, const char *keyring);
    void ima_audit_measurement(struct integrity_iint_cache *iint,
    diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
    index bf22de8b7ce0..4f39fb93f278 100644
    --- a/security/integrity/ima/ima_api.c
    +++ b/security/integrity/ima/ima_api.c
    @@ -162,7 +162,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,

    /**
    * ima_get_action - appraise & measure decision based on policy.
    - * @inode: pointer to inode to measure
    + * @inode: pointer to the inode associated with the object being validated
    * @cred: pointer to credentials structure to validate
    * @secid: secid of the task being validated
    * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
    diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
    index a9649b04b9f1..6c52bf7ea7f0 100644
    --- a/security/integrity/ima/ima_appraise.c
    +++ b/security/integrity/ima/ima_appraise.c
    @@ -328,7 +328,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,

    rc = is_binary_blacklisted(digest, digestsize);
    if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
    - process_buffer_measurement(digest, digestsize,
    + process_buffer_measurement(NULL, digest, digestsize,
    "blacklisted-hash", NONE,
    pcr, NULL);
    }
    diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
    index aaae80c4e376..1c68c500c26f 100644
    --- a/security/integrity/ima/ima_asymmetric_keys.c
    +++ b/security/integrity/ima/ima_asymmetric_keys.c
    @@ -58,7 +58,7 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
    * if the IMA policy is configured to measure a key linked
    * to the given keyring.
    */
    - process_buffer_measurement(payload, payload_len,
    + process_buffer_measurement(NULL, payload, payload_len,
    keyring->description, KEY_CHECK, 0,
    keyring->description);
    }
    diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
    index 8351b2fd48e0..8a91711ca79b 100644
    --- a/security/integrity/ima/ima_main.c
    +++ b/security/integrity/ima/ima_main.c
    @@ -726,6 +726,7 @@ int ima_load_data(enum kernel_load_data_id id)

    /*
    * process_buffer_measurement - Measure the buffer to ima log.
    + * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
    * @buf: pointer to the buffer that needs to be added to the log.
    * @size: size of buffer(in bytes).
    * @eventname: event name to be used for the buffer entry.
    @@ -735,7 +736,7 @@ int ima_load_data(enum kernel_load_data_id id)
    *
    * Based on policy, the buffer is measured into the ima log.
    */
    -void process_buffer_measurement(const void *buf, int size,
    +void process_buffer_measurement(struct inode *inode, const void *buf, int size,
    const char *eventname, enum ima_hooks func,
    int pcr, const char *keyring)
    {
    @@ -768,7 +769,7 @@ void process_buffer_measurement(const void *buf, int size,
    */
    if (func) {
    security_task_getsecid(current, &secid);
    - action = ima_get_action(NULL, current_cred(), secid, 0, func,
    + action = ima_get_action(inode, current_cred(), secid, 0, func,
    &pcr, &template, keyring);
    if (!(action & IMA_MEASURE))
    return;
    @@ -823,16 +824,26 @@ void process_buffer_measurement(const void *buf, int size,

    /**
    * ima_kexec_cmdline - measure kexec cmdline boot args
    + * @kernel_fd: file descriptor of the kexec kernel being loaded
    * @buf: pointer to buffer
    * @size: size of buffer
    *
    * Buffers can only be measured, not appraised.
    */
    -void ima_kexec_cmdline(const void *buf, int size)
    +void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
    {
    - if (buf && size != 0)
    - process_buffer_measurement(buf, size, "kexec-cmdline",
    - KEXEC_CMDLINE, 0, NULL);
    + struct fd f;
    +
    + if (!buf || !size)
    + return;
    +
    + f = fdget(kernel_fd);
    + if (!f.file)
    + return;
    +
    + process_buffer_measurement(file_inode(f.file), buf, size,
    + "kexec-cmdline", KEXEC_CMDLINE, 0, NULL);
    + fdput(f);
    }

    static int __init init_ima(void)
    diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
    index 5eb14b567a31..294323b36d06 100644
    --- a/security/integrity/ima/ima_policy.c
    +++ b/security/integrity/ima/ima_policy.c
    @@ -443,13 +443,9 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
    {
    int i;

    - if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
    - if ((rule->flags & IMA_FUNC) && (rule->func == func)) {
    - if (func == KEY_CHECK)
    - return ima_match_keyring(rule, keyring, cred);
    - return true;
    - }
    - return false;
    + if (func == KEY_CHECK) {
    + return (rule->flags & IMA_FUNC) && (rule->func == func) &&
    + ima_match_keyring(rule, keyring, cred);
    }
    if ((rule->flags & IMA_FUNC) &&
    (rule->func != func && func != POST_SETATTR))
    @@ -1007,10 +1003,9 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
    if (entry->action & ~(MEASURE | DONT_MEASURE))
    return false;

    - if (entry->flags & ~(IMA_FUNC | IMA_PCR))
    - return false;
    -
    - if (ima_rule_contains_lsm_cond(entry))
    + if (entry->flags & ~(IMA_FUNC | IMA_FSMAGIC | IMA_UID |
    + IMA_FOWNER | IMA_FSUUID |
    + IMA_EUID | IMA_PCR | IMA_FSNAME))
    return false;

    break;
    diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
    index 56ce24a18b66..69a8626a35c0 100644
    --- a/security/integrity/ima/ima_queue_keys.c
    +++ b/security/integrity/ima/ima_queue_keys.c
    @@ -158,7 +158,7 @@ void ima_process_queued_keys(void)

    list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
    if (!timer_expired)
    - process_buffer_measurement(entry->payload,
    + process_buffer_measurement(NULL, entry->payload,
    entry->payload_len,
    entry->keyring_name,
    KEY_CHECK, 0,
    --
    2.25.1
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