On 2020-12-12 10:02:48, Tushar Sugandhi wrote:
> System administrators should be able to limit which kernel subsystems
> they want to measure the critical data for. To enable that, an IMA policy
> condition to choose specific kernel subsystems is needed. This policy
> condition would constrain the measurement of the critical data based on
> a label for the given subsystems.
>
> Add a new IMA policy condition - "data_source:=" to the IMA func
> CRITICAL_DATA to allow measurement of various kernel subsystems. This
> policy condition would enable the system administrators to restrict the
> measurement to the labels listed in "data_source:=".
>
> Limit the measurement to the labels that are specified in the IMA
> policy - CRITICAL_DATA+"data_source:=". If "data_sources:=" is not
> provided with the func CRITICAL_DATA, the data from all the
> supported kernel subsystems is measured.
>
> Signed-off-by: Tushar Sugandhi <tusha...@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhi...@linux.microsoft.com>
Tyler
> ---
> Documentation/ABI/testing/ima_policy | 2 ++
> security/integrity/ima/ima_policy.c | 37 +++++++++++++++++++++++++---
> 2 files changed, 36 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/ABI/testing/ima_policy
> b/Documentation/ABI/testing/ima_policy
> index 6ec7daa87cba..0f4ee9e0a455 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -52,6 +52,8 @@ Description:
> template:= name of a defined IMA template type
> (eg, ima-ng). Only valid when action is "measure".
> pcr:= decimal value
> + data_source:= [label]
> + label:= a unique string used for grouping and limiting
> critical data.
>
> default policy:
> # PROC_SUPER_MAGIC
> diff --git a/security/integrity/ima/ima_policy.c
> b/security/integrity/ima/ima_policy.c
> index d45c2dbb6d45..fea996a9e26c 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -34,6 +34,7 @@
> #define IMA_PCR 0x0100
> #define IMA_FSNAME 0x0200
> #define IMA_KEYRINGS 0x0400
> +#define IMA_DATA_SOURCE 0x0800
>
> #define UNKNOWN 0
> #define MEASURE 0x0001 /* same as IMA_MEASURE */
> @@ -85,6 +86,7 @@ struct ima_rule_entry {
> } lsm[MAX_LSM_RULES];
> char *fsname;
> struct ima_rule_opt_list *keyrings; /* Measure keys added to these
> keyrings */
> + struct ima_rule_opt_list *data_source; /* Measure data from this source
> */
> struct ima_template_desc *template;
> };
>
> @@ -480,7 +482,11 @@ static bool ima_match_rule_data(struct ima_rule_entry
> *rule,
> opt_list = rule->keyrings;
> break;
> case CRITICAL_DATA:
> - return true;
> + if (!rule->data_source)
> + return true;
> +
> + opt_list = rule->data_source;
> + break;
> default:
> return false;
> }
> @@ -925,7 +931,7 @@ enum {
> Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
> Opt_appraise_type, Opt_appraise_flag,
> Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
> - Opt_err
> + Opt_data_source, Opt_err
> };
>
> static const match_table_t policy_tokens = {
> @@ -962,6 +968,7 @@ static const match_table_t policy_tokens = {
> {Opt_pcr, "pcr=%s"},
> {Opt_template, "template=%s"},
> {Opt_keyrings, "keyrings=%s"},
> + {Opt_data_source, "data_source=%s"},
> {Opt_err, NULL}
> };
>
> @@ -1129,7 +1136,8 @@ static bool ima_validate_rule(struct ima_rule_entry
> *entry)
> if (entry->action & ~(MEASURE | DONT_MEASURE))
> return false;
>
> - if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR))
> + if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
> + IMA_DATA_SOURCE))
> return false;
>
> if (ima_rule_contains_lsm_cond(entry))
> @@ -1339,6 +1347,23 @@ static int ima_parse_rule(char *rule, struct
> ima_rule_entry *entry)
>
> entry->flags |= IMA_KEYRINGS;
> break;
> + case Opt_data_source:
> + ima_log_string(ab, "data_source", args[0].from);
> +
> + if (entry->data_source) {
> + result = -EINVAL;
> + break;
> + }
> +
> + entry->data_source = ima_alloc_rule_opt_list(args);
> + if (IS_ERR(entry->data_source)) {
> + result = PTR_ERR(entry->data_source);
> + entry->data_source = NULL;
> + break;
> + }
> +
> + entry->flags |= IMA_DATA_SOURCE;
> + break;
> case Opt_fsuuid:
> ima_log_string(ab, "fsuuid", args[0].from);
>
> @@ -1719,6 +1744,12 @@ int ima_policy_show(struct seq_file *m, void *v)
> seq_puts(m, " ");
> }
>
> + if (entry->flags & IMA_DATA_SOURCE) {
> + seq_puts(m, "data_source=");
> + ima_show_rule_opt_list(m, entry->data_source);
> + seq_puts(m, " ");
> + }
> +
> if (entry->flags & IMA_PCR) {
> snprintf(tbuf, sizeof(tbuf), "%d", entry->pcr);
> seq_printf(m, pt(Opt_pcr), tbuf);
> --
> 2.17.1
>
