On 4/29/22 07:25, Mimi Zohar wrote:
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));
You seem to be doing this above as well in ima_get_verity_digest(). I guess the above one could go.
- 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)
Acked-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
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