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-rw-r--r--Documentation/ABI/testing/ima_policy31
-rw-r--r--Documentation/security/IMA-templates.rst4
-rw-r--r--security/integrity/digsig.c3
-rw-r--r--security/integrity/ima/ima_appraise.c114
-rw-r--r--security/integrity/ima/ima_policy.c46
-rw-r--r--security/integrity/ima/ima_template_lib.c4
-rw-r--r--security/integrity/integrity.h26
7 files changed, 209 insertions, 19 deletions
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 0a8caed393e3..db17fc8a0c9f 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -48,7 +48,15 @@ Description:
fgroup:= decimal value
lsm: are LSM specific
option:
- appraise_type:= [imasig] [imasig|modsig]
+ appraise_type:= [imasig] | [imasig|modsig] | [sigv3]
+ where 'imasig' is the original or the signature
+ format v2.
+ where 'modsig' is an appended signature,
+ where 'sigv3' is the signature format v3. (Currently
+ limited to fsverity digest based signatures
+ stored in security.ima xattr. Requires
+ specifying "digest_type=verity" first.)
+
appraise_flag:= [check_blacklist]
Currently, blacklist check is only for files signed with appended
signature.
@@ -159,3 +167,24 @@ Description:
measure func=FILE_CHECK digest_type=verity \
template=ima-ngv2
+
+ Example of 'measure' and 'appraise' rules requiring fs-verity
+ signatures (format version 3) stored in security.ima xattr.
+
+ The 'measure' rule specifies the 'ima-sigv3' template option,
+ which includes the indication of type of digest and the file
+ signature in the measurement list.
+
+ measure func=BPRM_CHECK digest_type=verity \
+ template=ima-sigv3
+
+
+ The 'appraise' rule specifies the type and signature format
+ version (sigv3) required.
+
+ appraise func=BPRM_CHECK digest_type=verity \
+ appraise_type=sigv3
+
+ All of these policy rules could, for example, be constrained
+ either based on a filesystem's UUID (fsuuid) or based on LSM
+ labels.
diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
index 09b5fac38195..15b4add314fc 100644
--- a/Documentation/security/IMA-templates.rst
+++ b/Documentation/security/IMA-templates.rst
@@ -71,8 +71,8 @@ descriptors by adding their identifier to the format string
(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;
- - 'sig': the file signature, or the EVM portable signature if the file
- signature is not found;
+ - 'sig': the file signature, based on either the file's/fsverity's digest[1],
+ or the EVM portable signature, if 'security.ima' contains a file hash.
- 'modsig' the appended file signature;
- 'buf': the buffer data that was used to generate the hash without size limitations;
- 'evmsig': the EVM portable signature;
diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index c8c8a4a4e7a0..8a82a6c7f48a 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -75,7 +75,8 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
/* v1 API expect signature without xattr type */
return digsig_verify(keyring, sig + 1, siglen - 1, digest,
digestlen);
- case 2:
+ case 2: /* regular file data hash based signature */
+ case 3: /* struct ima_file_id data based signature */
return asymmetric_verify(keyring, sig, siglen, digest,
digestlen);
}
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 17232bbfb9f9..cdb84dccd24e 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -13,7 +13,9 @@
#include <linux/magic.h>
#include <linux/ima.h>
#include <linux/evm.h>
+#include <linux/fsverity.h>
#include <keys/system_keyring.h>
+#include <uapi/linux/fsverity.h>
#include "ima.h"
@@ -183,13 +185,18 @@ enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value,
return ima_hash_algo;
switch (xattr_value->type) {
+ case IMA_VERITY_DIGSIG:
+ sig = (typeof(sig))xattr_value;
+ if (sig->version != 3 || xattr_len <= sizeof(*sig) ||
+ sig->hash_algo >= HASH_ALGO__LAST)
+ return ima_hash_algo;
+ return sig->hash_algo;
case EVM_IMA_XATTR_DIGSIG:
sig = (typeof(sig))xattr_value;
if (sig->version != 2 || xattr_len <= sizeof(*sig)
|| sig->hash_algo >= HASH_ALGO__LAST)
return ima_hash_algo;
return sig->hash_algo;
- break;
case IMA_XATTR_DIGEST_NG:
/* first byte contains algorithm id */
ret = xattr_value->data[0];
@@ -226,6 +233,40 @@ int ima_read_xattr(struct dentry *dentry,
}
/*
+ * calc_file_id_hash - calculate the hash of the ima_file_id struct data
+ * @type: xattr type [enum evm_ima_xattr_type]
+ * @algo: hash algorithm [enum hash_algo]
+ * @digest: pointer to the digest to be hashed
+ * @hash: (out) pointer to the hash
+ *
+ * IMA signature version 3 disambiguates the data that is signed by
+ * indirectly signing the hash of the ima_file_id structure data.
+ *
+ * Signing the ima_file_id struct is currently only supported for
+ * IMA_VERITY_DIGSIG type xattrs.
+ *
+ * Return 0 on success, error code otherwise.
+ */
+static int calc_file_id_hash(enum evm_ima_xattr_type type,
+ enum hash_algo algo, const u8 *digest,
+ struct ima_digest_data *hash)
+{
+ struct ima_file_id file_id = {
+ .hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo};
+ unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];
+
+ if (type != IMA_VERITY_DIGSIG)
+ return -EINVAL;
+
+ memcpy(file_id.hash, digest, hash_digest_size[algo]);
+
+ hash->algo = algo;
+ hash->length = hash_digest_size[algo];
+
+ return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash);
+}
+
+/*
* xattr_verify - verify xattr digest or signature
*
* Verify whether the hash or signature matches the file contents.
@@ -236,7 +277,10 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
struct evm_ima_xattr_data *xattr_value, int xattr_len,
enum integrity_status *status, const char **cause)
{
+ struct ima_max_digest_data hash;
+ struct signature_v2_hdr *sig;
int rc = -EINVAL, hash_start = 0;
+ int mask;
switch (xattr_value->type) {
case IMA_XATTR_DIGEST_NG:
@@ -246,7 +290,10 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
case IMA_XATTR_DIGEST:
if (*status != INTEGRITY_PASS_IMMUTABLE) {
if (iint->flags & IMA_DIGSIG_REQUIRED) {
- *cause = "IMA-signature-required";
+ if (iint->flags & IMA_VERITY_REQUIRED)
+ *cause = "verity-signature-required";
+ else
+ *cause = "IMA-signature-required";
*status = INTEGRITY_FAIL;
break;
}
@@ -274,6 +321,20 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
break;
case EVM_IMA_XATTR_DIGSIG:
set_bit(IMA_DIGSIG, &iint->atomic_flags);
+
+ mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
+ if ((iint->flags & mask) == mask) {
+ *cause = "verity-signature-required";
+ *status = INTEGRITY_FAIL;
+ break;
+ }
+
+ sig = (typeof(sig))xattr_value;
+ if (sig->version >= 3) {
+ *cause = "invalid-signature-version";
+ *status = INTEGRITY_FAIL;
+ break;
+ }
rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
(const char *)xattr_value,
xattr_len,
@@ -297,6 +358,44 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
*status = INTEGRITY_PASS;
}
break;
+ case IMA_VERITY_DIGSIG:
+ set_bit(IMA_DIGSIG, &iint->atomic_flags);
+
+ if (iint->flags & IMA_DIGSIG_REQUIRED) {
+ if (!(iint->flags & IMA_VERITY_REQUIRED)) {
+ *cause = "IMA-signature-required";
+ *status = INTEGRITY_FAIL;
+ break;
+ }
+ }
+
+ sig = (typeof(sig))xattr_value;
+ if (sig->version != 3) {
+ *cause = "invalid-signature-version";
+ *status = INTEGRITY_FAIL;
+ break;
+ }
+
+ rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
+ iint->ima_hash->digest, &hash.hdr);
+ if (rc) {
+ *cause = "sigv3-hashing-error";
+ *status = INTEGRITY_FAIL;
+ break;
+ }
+
+ rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
+ (const char *)xattr_value,
+ xattr_len, hash.digest,
+ hash.hdr.length);
+ if (rc) {
+ *cause = "invalid-verity-signature";
+ *status = INTEGRITY_FAIL;
+ } else {
+ *status = INTEGRITY_PASS;
+ }
+
+ break;
default:
*status = INTEGRITY_UNKNOWN;
*cause = "unknown-ima-data";
@@ -396,8 +495,15 @@ int ima_appraise_measurement(enum ima_hooks func,
if (rc && rc != -ENODATA)
goto out;
- cause = iint->flags & IMA_DIGSIG_REQUIRED ?
- "IMA-signature-required" : "missing-hash";
+ if (iint->flags & IMA_DIGSIG_REQUIRED) {
+ if (iint->flags & IMA_VERITY_REQUIRED)
+ cause = "verity-signature-required";
+ else
+ cause = "IMA-signature-required";
+ } else {
+ cause = "missing-hash";
+ }
+
status = INTEGRITY_NOLABEL;
if (file->f_mode & FMODE_CREATED)
iint->flags |= IMA_NEW_FILE;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 390a8faa77f9..73917413365b 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1310,6 +1310,18 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
!(entry->flags & IMA_MODSIG_ALLOWED))
return false;
+ /*
+ * Unlike for regular IMA 'appraise' policy rules where security.ima
+ * xattr may contain either a file hash or signature, the security.ima
+ * xattr for fsverity must contain a file signature (sigv3). Ensure
+ * that 'appraise' rules for fsverity require file signatures by
+ * checking the IMA_DIGSIG_REQUIRED flag is set.
+ */
+ if (entry->action == APPRAISE &&
+ (entry->flags & IMA_VERITY_REQUIRED) &&
+ !(entry->flags & IMA_DIGSIG_REQUIRED))
+ return false;
+
return true;
}
@@ -1727,21 +1739,37 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
break;
case Opt_digest_type:
ima_log_string(ab, "digest_type", args[0].from);
- if ((strcmp(args[0].from, "verity")) == 0)
+ if (entry->flags & IMA_DIGSIG_REQUIRED)
+ result = -EINVAL;
+ else 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)
- entry->flags |= IMA_DIGSIG_REQUIRED;
- else if (IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG) &&
- strcmp(args[0].from, "imasig|modsig") == 0)
- entry->flags |= IMA_DIGSIG_REQUIRED |
+
+ if ((strcmp(args[0].from, "imasig")) == 0) {
+ if (entry->flags & IMA_VERITY_REQUIRED)
+ result = -EINVAL;
+ else
+ entry->flags |= IMA_DIGSIG_REQUIRED;
+ } else if (strcmp(args[0].from, "sigv3") == 0) {
+ /* Only fsverity supports sigv3 for now */
+ if (entry->flags & IMA_VERITY_REQUIRED)
+ entry->flags |= IMA_DIGSIG_REQUIRED;
+ else
+ result = -EINVAL;
+ } else if (IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG) &&
+ strcmp(args[0].from, "imasig|modsig") == 0) {
+ if (entry->flags & IMA_VERITY_REQUIRED)
+ result = -EINVAL;
+ else
+ entry->flags |= IMA_DIGSIG_REQUIRED |
IMA_MODSIG_ALLOWED;
- else
+ } else {
result = -EINVAL;
+ }
break;
case Opt_appraise_flag:
ima_log_string(ab, "appraise_flag", args[0].from);
@@ -2183,7 +2211,9 @@ int ima_policy_show(struct seq_file *m, void *v)
if (entry->template)
seq_printf(m, "template=%s ", entry->template->name);
if (entry->flags & IMA_DIGSIG_REQUIRED) {
- if (entry->flags & IMA_MODSIG_ALLOWED)
+ if (entry->flags & IMA_VERITY_REQUIRED)
+ seq_puts(m, "appraise_type=sigv3 ");
+ else if (entry->flags & IMA_MODSIG_ALLOWED)
seq_puts(m, "appraise_type=imasig|modsig ");
else
seq_puts(m, "appraise_type=imasig ");
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 08fd74217e2c..c877f01a5471 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -535,7 +535,9 @@ int ima_eventsig_init(struct ima_event_data *event_data,
{
struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
- if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
+ if (!xattr_value ||
+ (xattr_value->type != EVM_IMA_XATTR_DIGSIG &&
+ xattr_value->type != IMA_VERITY_DIGSIG))
return ima_eventevmsig_init(event_data, field_data);
return ima_write_template_field_data(xattr_value, event_data->xattr_len,
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 04e2b99cd912..7167a6e99bdc 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -79,6 +79,7 @@ enum evm_ima_xattr_type {
EVM_IMA_XATTR_DIGSIG,
IMA_XATTR_DIGEST_NG,
EVM_XATTR_PORTABLE_DIGSIG,
+ IMA_VERITY_DIGSIG,
IMA_XATTR_LAST
};
@@ -93,7 +94,7 @@ struct evm_xattr {
u8 digest[SHA1_DIGEST_SIZE];
} __packed;
-#define IMA_MAX_DIGEST_SIZE 64
+#define IMA_MAX_DIGEST_SIZE HASH_MAX_DIGESTSIZE
struct ima_digest_data {
u8 algo;
@@ -122,7 +123,14 @@ struct ima_max_digest_data {
} __packed;
/*
- * signature format v2 - for using with asymmetric keys
+ * signature header format v2 - for using with asymmetric keys
+ *
+ * The signature_v2_hdr struct includes a signature format version
+ * to simplify defining new signature formats.
+ *
+ * signature format:
+ * version 2: regular file data hash based signature
+ * version 3: struct ima_file_id data based signature
*/
struct signature_v2_hdr {
uint8_t type; /* xattr type */
@@ -133,6 +141,20 @@ struct signature_v2_hdr {
uint8_t sig[]; /* signature payload */
} __packed;
+/*
+ * IMA signature version 3 disambiguates the data that is signed, by
+ * indirectly signing the hash of the ima_file_id structure data,
+ * containing either the fsverity_descriptor struct digest or, in the
+ * future, the regular IMA file hash.
+ *
+ * (The hash of the ima_file_id structure is only of the portion used.)
+ */
+struct ima_file_id {
+ __u8 hash_type; /* xattr type [enum evm_ima_xattr_type] */
+ __u8 hash_algorithm; /* Digest algorithm [enum hash_algo] */
+ __u8 hash[HASH_MAX_DIGESTSIZE];
+} __packed;
+
/* integrity data associated with an inode */
struct integrity_iint_cache {
struct rb_node rb_node; /* rooted in integrity_iint_tree */
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.