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    Subject[PATCH V31 24/25] lockdown: Print current->comm in restriction messages
    From
    From: David Howells <dhowells@redhat.com>

    Print the content of current->comm in messages generated by lockdown to
    indicate a restriction that was hit. This makes it a bit easier to find
    out what caused the message.

    The message now patterned something like:

    Lockdown: <comm>: <what> is restricted; see man kernel_lockdown.7

    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Matthew Garrett <mjg59@google.com>
    ---
    include/linux/ima.h | 9 ++++++
    kernel/kexec_file.c | 7 +++-
    security/integrity/ima/ima.h | 2 ++
    security/integrity/ima/ima_main.c | 2 +-
    security/integrity/ima/ima_policy.c | 50 +++++++++++++++++++++++++++++
    security/lock_down.c | 4 +--
    6 files changed, 70 insertions(+), 4 deletions(-)

    diff --git a/include/linux/ima.h b/include/linux/ima.h
    index b5e16b8c50b7..05921227d700 100644
    --- a/include/linux/ima.h
    +++ b/include/linux/ima.h
    @@ -127,4 +127,13 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
    return 0;
    }
    #endif /* CONFIG_IMA_APPRAISE */
    +
    +#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
    +extern bool ima_appraise_signature(enum kernel_read_file_id func);
    +#else
    +static inline bool ima_appraise_kexec_signature(enum kernel_read_file_id func)
    +{
    + return false;
    +}
    +#endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */
    #endif /* _LINUX_IMA_H */
    diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
    index a1cc37c8b43b..7599039623a7 100644
    --- a/kernel/kexec_file.c
    +++ b/kernel/kexec_file.c
    @@ -240,7 +240,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,

    ret = 0;

    - if (kernel_is_locked_down(reason, LOCKDOWN_INTEGRITY)) {
    + /* If IMA is guaranteed to appraise a signature on the kexec
    + * image, permit it even if the kernel is otherwise locked
    + * down.
    + */
    + if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
    + kernel_is_locked_down(reason, LOCKDOWN_INTEGRITY)) {
    ret = -EPERM;
    goto out;
    }
    diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
    index cc12f3449a72..fe03cc6f1ca4 100644
    --- a/security/integrity/ima/ima.h
    +++ b/security/integrity/ima/ima.h
    @@ -115,6 +115,8 @@ struct ima_kexec_hdr {
    u64 count;
    };

    +extern const int read_idmap[];
    +
    #ifdef CONFIG_HAVE_IMA_KEXEC
    void ima_load_kexec_buffer(void);
    #else
    diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
    index 4ffac4f5c647..106f06dee9d1 100644
    --- a/security/integrity/ima/ima_main.c
    +++ b/security/integrity/ima/ima_main.c
    @@ -442,7 +442,7 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
    return 0;
    }

    -static const int read_idmap[READING_MAX_ID] = {
    +const int read_idmap[READING_MAX_ID] = {
    [READING_FIRMWARE] = FIRMWARE_CHECK,
    [READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK,
    [READING_MODULE] = MODULE_CHECK,
    diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
    index 122797023bdb..f8f1cdb74a4f 100644
    --- a/security/integrity/ima/ima_policy.c
    +++ b/security/integrity/ima/ima_policy.c
    @@ -1341,3 +1341,53 @@ int ima_policy_show(struct seq_file *m, void *v)
    return 0;
    }
    #endif /* CONFIG_IMA_READ_POLICY */
    +
    +#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
    +/*
    + * ima_appraise_signature: whether IMA will appraise a given function using
    + * an IMA digital signature. This is restricted to cases where the kernel
    + * has a set of built-in trusted keys in order to avoid an attacker simply
    + * loading additional keys.
    + */
    +bool ima_appraise_signature(enum kernel_read_file_id id)
    +{
    + struct ima_rule_entry *entry;
    + bool found = false;
    + enum ima_hooks func;
    +
    + if (id >= READING_MAX_ID)
    + return false;
    +
    + func = read_idmap[id] ?: FILE_CHECK;
    +
    + rcu_read_lock();
    + list_for_each_entry_rcu(entry, ima_rules, list) {
    + if (entry->action != APPRAISE)
    + continue;
    +
    + /*
    + * A generic entry will match, but otherwise require that it
    + * match the func we're looking for
    + */
    + if (entry->func && entry->func != func)
    + continue;
    +
    + /*
    + * We require this to be a digital signature, not a raw IMA
    + * hash.
    + */
    + if (entry->flags & IMA_DIGSIG_REQUIRED)
    + found = true;
    +
    + /*
    + * We've found a rule that matches, so break now even if it
    + * didn't require a digital signature - a later rule that does
    + * won't override it, so would be a false positive.
    + */
    + break;
    + }
    +
    + rcu_read_unlock();
    + return found;
    +}
    +#endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */
    diff --git a/security/lock_down.c b/security/lock_down.c
    index 0f9ef4c30aa8..6bcffd0bb200 100644
    --- a/security/lock_down.c
    +++ b/security/lock_down.c
    @@ -70,8 +70,8 @@ bool __kernel_is_locked_down(const char *what, enum lockdown_level level,
    bool first)
    {
    if ((kernel_locked_down >= level) && what && first)
    - pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n",
    - what);
    + pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
    + current->comm, what);
    return (kernel_locked_down >= level);
    }
    EXPORT_SYMBOL(__kernel_is_locked_down);
    --
    2.21.0.392.gf8f6787159e-goog
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