On Fri, Oct 21, 2016 at 5:44 AM, Thiago Jung Bauermann
<bauerman at linux.vnet.ibm.com> wrote:
> From: Mimi Zohar <zohar at linux.vnet.ibm.com>
>
> In preparation for serializing the binary_runtime_measurements, this patch
> maintains the amount of memory required.
>
> Changelog v5:
> - replace CONFIG_KEXEC_FILE with architecture CONFIG_HAVE_IMA_KEXEC (Thiago)
>
> Changelog v3:
> - include the ima_kexec_hdr size in the binary_runtime_measurement size.
>
> Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
> ---
> security/integrity/ima/Kconfig | 12 +++++++++
> security/integrity/ima/ima.h | 1 +
> security/integrity/ima/ima_queue.c | 53 ++++++++++++++++++++++++++++++++++++--
> 3 files changed, 64 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 5487827fa86c..370eb2f4dd37 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -27,6 +27,18 @@ config IMA
> to learn more about IMA.
> If unsure, say N.
>
> +config IMA_KEXEC
> + bool "Enable carrying the IMA measurement list across a soft boot"
> + depends on IMA && TCG_TPM && HAVE_IMA_KEXEC
> + default n
> + help
> + TPM PCRs are only reset on a hard reboot. In order to validate
> + a TPM's quote after a soft boot, the IMA measurement list of the
> + running kernel must be saved and restored on boot.
> +
> + Depending on the IMA policy, the measurement list can grow to
> + be very large.
> +
> config IMA_MEASURE_PCR_IDX
> int
> depends on IMA
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 51dc8d57d64d..ea1dcc452911 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -143,6 +143,7 @@ void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
> struct ima_template_desc *ima_template_desc_current(void);
> int ima_restore_measurement_entry(struct ima_template_entry *entry);
> int ima_restore_measurement_list(loff_t bufsize, void *buf);
> +unsigned long ima_get_binary_runtime_size(void);
> int ima_init_template(void);
>
> /*
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index 12d1b040bca9..3a3cc2a45645 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -29,6 +29,11 @@
> #define AUDIT_CAUSE_LEN_MAX 32
>
> LIST_HEAD(ima_measurements); /* list of all measurements */
> +#ifdef CONFIG_IMA_KEXEC
> +static unsigned long binary_runtime_size;
> +#else
> +static unsigned long binary_runtime_size = ULONG_MAX;
> +#endif
>
> /* key: inode (before secure-hashing a file) */
> struct ima_h_table ima_htable = {
> @@ -64,6 +69,24 @@ static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
> return ret;
> }
>
> +/*
> + * Calculate the memory required for serializing a single
> + * binary_runtime_measurement list entry, which contains a
> + * couple of variable length fields (e.g template name and data).
> + */
> +static int get_binary_runtime_size(struct ima_template_entry *entry)
> +{
> + int size = 0;
> +
> + size += sizeof(u32); /* pcr */
> + size += sizeof(entry->digest);
> + size += sizeof(int); /* template name size field */
> + size += strlen(entry->template_desc->name);
> + size += sizeof(entry->template_data_len);
> + size += entry->template_data_len;
> + return size;
> +}
> +
strlen returns len without '\0'. I cannot see how you would know how
to read it back?
> /* ima_add_template_entry helper function:
> * - Add template entry to the measurement list and hash table, for
> * all entries except those carried across kexec.
> @@ -90,9 +113,30 @@ static int ima_add_digest_entry(struct ima_template_entry *entry, int flags)
> key = ima_hash_key(entry->digest);
> hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
> }
> +
> + if (binary_runtime_size != ULONG_MAX) {
> + int size;
> +
> + size = get_binary_runtime_size(entry);
> + binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
> + binary_runtime_size + size : ULONG_MAX;
> + }
> return 0;
> }
>
> +/*
> + * Return the amount of memory required for serializing the
> + * entire binary_runtime_measurement list, including the ima_kexec_hdr
> + * structure.
> + */
> +unsigned long ima_get_binary_runtime_size(void)
> +{
> + if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
> + return ULONG_MAX;
> + else
> + return binary_runtime_size + sizeof(struct ima_kexec_hdr);
> +};
> +
> static int ima_pcr_extend(const u8 *hash, int pcr)
> {
> int result = 0;
> @@ -106,8 +150,13 @@ static int ima_pcr_extend(const u8 *hash, int pcr)
> return result;
> }
>
> -/* Add template entry to the measurement list and hash table,
> - * and extend the pcr.
> +/*
> + * Add template entry to the measurement list and hash table, and
> + * extend the pcr.
> + *
> + * On systems which support carrying the IMA measurement list across
> + * kexec, maintain the total memory size required for serializing the
> + * binary_runtime_measurements.
> */
> int ima_add_template_entry(struct ima_template_entry *entry, int violation,
> const char *op, struct inode *inode,
> --
> 2.7.4
>
>
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--
Thanks,
Dmitry
