Permit fsverity's file digest (a hash of struct fsverity_descriptor) to
be included in the IMA measurement list, based on the new measurement
policy rule 'digest_type=verity' option.
To differentiate between a regular IMA file hash from an fsverity's
file digest, use the new d-ngv2 format field included in the ima-ngv2
template.
The following policy rule requires fsverity file digests and specifies
the new 'ima-ngv2' template, which contains the new 'd-ngv2' field. The
policy rule may be constrained, for example based on a fsuuid or LSM
label.
measure func=FILE_CHECK digest_type=verity template=ima-ngv2
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
Documentation/ABI/testing/ima_policy | 14 ++++++-
Documentation/security/IMA-templates.rst | 2 +-
security/integrity/ima/ima_api.c | 49 +++++++++++++++++++++--
security/integrity/ima/ima_main.c | 2 +-
security/integrity/ima/ima_policy.c | 38 +++++++++++++++++-
security/integrity/ima/ima_template_lib.c | 10 +++--
security/integrity/integrity.h | 1 +
7 files changed, 105 insertions(+), 11 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 839fab811b18..0a8caed393e3 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -27,8 +27,9 @@ Description:
[fowner=] [fgroup=]]
lsm: [[subj_user=] [subj_role=] [subj_type=]
[obj_user=] [obj_role=] [obj_type=]]
- option: [[appraise_type=]] [template=] [permit_directio]
- [appraise_flag=] [appraise_algos=] [keyrings=]
+ option: [digest_type=] [template=] [permit_directio]
+ [appraise_type=] [appraise_flag=]
+ [appraise_algos=] [keyrings=]
base:
func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
[FIRMWARE_CHECK]
@@ -51,6 +52,9 @@ Description:
appraise_flag:= [check_blacklist]
Currently, blacklist check is only for files signed with appended
signature.
+ digest_type:= verity
+ Require fs-verity's file digest instead of the
+ regular IMA file hash.
keyrings:= list of keyrings
(eg, .builtin_trusted_keys|.ima). Only valid
when action is "measure" and func is KEY_CHECK.
@@ -149,3 +153,9 @@ Description:
security.ima xattr of a file:
appraise func=SETXATTR_CHECK appraise_algos=sha256,sha384,sha512
+
+ Example of a 'measure' rule requiring fs-verity's digests
+ with indication of type of digest in the measurement list.
+
+ measure func=FILE_CHECK digest_type=verity \
+ template=ima-ngv2
diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
index eafc4e34f890..09b5fac38195 100644
--- a/Documentation/security/IMA-templates.rst
+++ b/Documentation/security/IMA-templates.rst
@@ -67,7 +67,7 @@ descriptors by adding their identifier to the format string
- 'n': the name of the event (i.e. the file name), with size up to 255 bytes;
- 'd-ng': the digest of the event, calculated with an arbitrary hash
algorithm (field format: <hash algo>:digest);
- - 'd-ngv2': same as d-ng, but prefixed with the "ima" digest type
+ - 'd-ngv2': same as d-ng, but prefixed with the "ima" or "verity" digest type
(field format: <digest type>:<hash algo>:digest);
- 'd-modsig': the digest of the event without the appended modsig;
- 'n-ng': the name of the event, without size limitations;
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index c6805af46211..d64ec031b1b4 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -14,6 +14,7 @@
#include <linux/xattr.h>
#include <linux/evm.h>
#include <linux/iversion.h>
+#include <linux/fsverity.h>
#include "ima.h"
@@ -200,6 +201,34 @@ int ima_get_action(struct user_namespace *mnt_userns, struct inode *inode,
allowed_algos);
}
+static int ima_get_verity_digest(struct integrity_iint_cache *iint,
+ struct ima_max_digest_data *hash)
+{
+ enum hash_algo verity_alg;
+ int ret;
+
+ /*
+ * On failure, 'measure' policy rules will result in a file data
+ * hash containing 0's.
+ */
+ ret = fsverity_get_digest(iint->inode, hash->digest, &verity_alg);
+ if (ret) {
+ memset(hash->digest, 0, sizeof(hash->digest));
+ return ret;
+ }
+
+ /*
+ * Unlike in the case of actually calculating the file hash, in
+ * the fsverity case regardless of the hash algorithm, return
+ * the verity digest to be included in the measurement list. A
+ * mismatch between the verity algorithm and the xattr signature
+ * algorithm, if one exists, will be detected later.
+ */
+ hash->hdr.algo = verity_alg;
+ hash->hdr.length = hash_digest_size[verity_alg];
+ return 0;
+}
+
/*
* ima_collect_measurement - collect file measurement
*
@@ -242,16 +271,30 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
*/
i_version = inode_query_iversion(inode);
hash.hdr.algo = algo;
+ hash.hdr.length = hash_digest_size[algo];
/* Initialize hash digest to 0's in case of failure */
memset(&hash.digest, 0, sizeof(hash.digest));
- if (buf)
+ if (iint->flags & IMA_VERITY_REQUIRED) {
+ result = ima_get_verity_digest(iint, &hash);
+ switch (result) {
+ case 0:
+ break;
+ case -ENODATA:
+ audit_cause = "no-verity-digest";
+ break;
+ default:
+ audit_cause = "invalid-verity-digest";
+ break;
+ }
+ } else if (buf) {
result = ima_calc_buffer_hash(buf, size, &hash.hdr);
- else
+ } else {
result = ima_calc_file_hash(file, &hash.hdr);
+ }
- if (result && result != -EBADF && result != -EINVAL)
+ if (result == -ENOMEM)
goto out;
length = sizeof(hash.hdr) + hash.hdr.length;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 1aebf63ad7a6..040b03ddc1c7 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -335,7 +335,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
- if (rc != 0 && rc != -EBADF && rc != -EINVAL)
+ if (rc == -ENOMEM)
goto out_locked;
if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index eea6e92500b8..390a8faa77f9 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1023,6 +1023,7 @@ enum policy_opt {
Opt_fowner_gt, Opt_fgroup_gt,
Opt_uid_lt, Opt_euid_lt, Opt_gid_lt, Opt_egid_lt,
Opt_fowner_lt, Opt_fgroup_lt,
+ Opt_digest_type,
Opt_appraise_type, Opt_appraise_flag, Opt_appraise_algos,
Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings,
Opt_label, Opt_err
@@ -1065,6 +1066,7 @@ static const match_table_t policy_tokens = {
{Opt_egid_lt, "egid<%s"},
{Opt_fowner_lt, "fowner<%s"},
{Opt_fgroup_lt, "fgroup<%s"},
+ {Opt_digest_type, "digest_type=%s"},
{Opt_appraise_type, "appraise_type=%s"},
{Opt_appraise_flag, "appraise_flag=%s"},
{Opt_appraise_algos, "appraise_algos=%s"},
@@ -1172,6 +1174,21 @@ static void check_template_modsig(const struct ima_template_desc *template)
#undef MSG
}
+/*
+ * Warn if the template does not contain the given field.
+ */
+static void check_template_field(const struct ima_template_desc *template,
+ const char *field, const char *msg)
+{
+ int i;
+
+ for (i = 0; i < template->num_fields; i++)
+ if (!strcmp(template->fields[i]->field_id, field))
+ return;
+
+ pr_notice_once("%s", msg);
+}
+
static bool ima_validate_rule(struct ima_rule_entry *entry)
{
/* Ensure that the action is set and is compatible with the flags */
@@ -1214,7 +1231,8 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
IMA_INMASK | IMA_EUID | IMA_PCR |
IMA_FSNAME | IMA_GID | IMA_EGID |
IMA_FGROUP | IMA_DIGSIG_REQUIRED |
- IMA_PERMIT_DIRECTIO | IMA_VALIDATE_ALGOS))
+ IMA_PERMIT_DIRECTIO | IMA_VALIDATE_ALGOS |
+ IMA_VERITY_REQUIRED))
return false;
break;
@@ -1707,6 +1725,13 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
LSM_SUBJ_TYPE,
AUDIT_SUBJ_TYPE);
break;
+ case Opt_digest_type:
+ ima_log_string(ab, "digest_type", args[0].from);
+ if ((strcmp(args[0].from, "verity")) == 0)
+ entry->flags |= IMA_VERITY_REQUIRED;
+ else
+ result = -EINVAL;
+ break;
case Opt_appraise_type:
ima_log_string(ab, "appraise_type", args[0].from);
if ((strcmp(args[0].from, "imasig")) == 0)
@@ -1797,6 +1822,15 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
check_template_modsig(template_desc);
}
+ /* d-ngv2 template field recommended for unsigned fs-verity digests */
+ if (!result && entry->action == MEASURE &&
+ entry->flags & IMA_VERITY_REQUIRED) {
+ template_desc = entry->template ? entry->template :
+ ima_template_desc_current();
+ check_template_field(template_desc, "d-ngv2",
+ "verity rules should include d-ngv2");
+ }
+
audit_log_format(ab, "res=%d", !result);
audit_log_end(ab);
return result;
@@ -2154,6 +2188,8 @@ int ima_policy_show(struct seq_file *m, void *v)
else
seq_puts(m, "appraise_type=imasig ");
}
+ if (entry->flags & IMA_VERITY_REQUIRED)
+ seq_puts(m, "digest_type=verity ");
if (entry->flags & IMA_CHECK_BLACKLIST)
seq_puts(m, "appraise_flag=check_blacklist ");
if (entry->flags & IMA_PERMIT_DIRECTIO)
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index ff82e699149c..2ebcf6cd92b8 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -32,12 +32,14 @@ enum data_formats {
enum digest_type {
DIGEST_TYPE_IMA,
+ DIGEST_TYPE_VERITY,
DIGEST_TYPE__LAST
};
-#define DIGEST_TYPE_NAME_LEN_MAX 4 /* including NULL */
+#define DIGEST_TYPE_NAME_LEN_MAX 7 /* including NULL */
static const char * const digest_type_name[DIGEST_TYPE__LAST] = {
- [DIGEST_TYPE_IMA] = "ima"
+ [DIGEST_TYPE_IMA] = "ima",
+ [DIGEST_TYPE_VERITY] = "verity"
};
static int ima_write_template_field_data(const void *data, const u32 datalen,
@@ -297,7 +299,7 @@ static int ima_eventdigest_init_common(const u8 *digest, u32 digestsize,
*
* where 'DATA_FMT_DIGEST' is the original digest format ('d')
* with a hash size limitation of 20 bytes,
- * where <digest type> is "ima",
+ * where <digest type> is either "ima" or "verity",
* where <hash algo> is the hash_algo_name[] string.
*/
u8 buffer[DIGEST_TYPE_NAME_LEN_MAX + CRYPTO_MAX_ALG_NAME + 2 +
@@ -435,6 +437,8 @@ int ima_eventdigest_ngv2_init(struct ima_event_data *event_data,
cur_digestsize = event_data->iint->ima_hash->length;
hash_algo = event_data->iint->ima_hash->algo;
+ if (event_data->iint->flags & IMA_VERITY_REQUIRED)
+ digest_type = DIGEST_TYPE_VERITY;
out:
return ima_eventdigest_init_common(cur_digest, cur_digestsize,
digest_type, hash_algo,
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 3510e413ea17..04e2b99cd912 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -40,6 +40,7 @@
#define IMA_FAIL_UNVERIFIABLE_SIGS 0x10000000
#define IMA_MODSIG_ALLOWED 0x20000000
#define IMA_CHECK_BLACKLIST 0x40000000
+#define IMA_VERITY_REQUIRED 0x80000000
#define IMA_DO_MASK (IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \
IMA_HASH | IMA_APPRAISE_SUBMASK)
--
2.27.0
