[PATCH v10 2/8] IMA: add support to measure buffer data hash

Tushar Sugandhi
2021-01-08T04:08:42Z

The original IMA buffer data measurement sizes were small (e.g. boot
command line), but the new buffer data measurement use cases have data
sizes that are a lot larger. Just as IMA measures the file data hash,
not the file data, IMA should similarly support the option for measuring
buffer data hash.

Introduce a boolean parameter to support measuring buffer data hash,
which would be much smaller, instead of the buffer itself.

Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
---
security/integrity/ima/ima.h | 3 +-
security/integrity/ima/ima_appraise.c | 2 +-
security/integrity/ima/ima_asymmetric_keys.c | 2 +-
security/integrity/ima/ima_main.c | 29 ++++++++++++++++----
security/integrity/ima/ima_queue_keys.c | 3 +-
5 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e5622ce8cbb1..0b4634515839 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -268,7 +268,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
struct ima_template_desc *template_desc);
void process_buffer_measurement(struct inode *inode, const void *buf, int size,
const char *eventname, enum ima_hooks func,
- int pcr, const char *func_data);
+ int pcr, const char *func_data,
+ bool buf_hash);
void ima_audit_measurement(struct integrity_iint_cache *iint,
const unsigned char *filename);
int ima_alloc_init_template(struct ima_event_data *event_data,
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 8361941ee0a1..46ffa38bab12 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -352,7 +352,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
process_buffer_measurement(NULL, digest, digestsize,
"blacklisted-hash", NONE,
- pcr, NULL);
+ pcr, NULL, false);
}

return rc;
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index 1c68c500c26f..a74095793936 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -60,5 +60,5 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
*/
process_buffer_measurement(NULL, payload, payload_len,
keyring->description, KEY_CHECK, 0,
- keyring->description);
+ keyring->description, false);
}
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index b4ed611cd2a4..494fb964497d 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -779,7 +779,7 @@ int ima_post_load_data(char *buf, loff_t size,
}

/*
- * process_buffer_measurement - Measure the buffer to ima log.
+ * process_buffer_measurement - Measure the buffer or the buffer data hash
* @inode: inode associated with the object being measured (NULL for KEY_CHECK)
* @buf: pointer to the buffer that needs to be added to the log.
* @size: size of buffer(in bytes).
@@ -787,12 +787,14 @@ int ima_post_load_data(char *buf, loff_t size,
* @func: IMA hook
* @pcr: pcr to extend the measurement
* @func_data: func specific data, may be NULL
+ * @buf_hash: measure buffer data hash
*
- * Based on policy, the buffer is measured into the ima log.
+ * Based on policy, either the buffer data or buffer data hash is measured
*/
void process_buffer_measurement(struct inode *inode, const void *buf, int size,
const char *eventname, enum ima_hooks func,
- int pcr, const char *func_data)
+ int pcr, const char *func_data,
+ bool buf_hash)
{
int ret = 0;
const char *audit_cause = "ENOMEM";
@@ -807,6 +809,8 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
struct ima_digest_data hdr;
char digest[IMA_MAX_DIGEST_SIZE];
} hash = {};
+ char digest_hash[IMA_MAX_DIGEST_SIZE];
+ int digest_hash_len = hash_digest_size[ima_hash_algo];
int violation = 0;
int action = 0;
u32 secid;
@@ -849,13 +853,27 @@ void process_buffer_measurement(struct inode *inode, const void *buf, int size,
goto out;
}

+ if (buf_hash) {
+ memcpy(digest_hash, hash.hdr.digest, digest_hash_len);
+
+ ret = ima_calc_buffer_hash(digest_hash, digest_hash_len,
+ iint.ima_hash);
+ if (ret < 0) {
+ audit_cause = "hashing_error";
+ goto out;
+ }
+
+ event_data.buf = digest_hash;
+ event_data.buf_len = digest_hash_len;
+ }
+
ret = ima_alloc_init_template(&event_data, &entry, template);
if (ret < 0) {
audit_cause = "alloc_entry";
goto out;
}

- ret = ima_store_template(entry, violation, NULL, buf, pcr);
+ ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr);
if (ret < 0) {
audit_cause = "store_entry";
ima_free_template_entry(entry);
@@ -890,7 +908,8 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
return;

process_buffer_measurement(file_inode(f.file), buf, size,
- "kexec-cmdline", KEXEC_CMDLINE, 0, NULL);
+ "kexec-cmdline", KEXEC_CMDLINE, 0, NULL,
+ false);
fdput(f);
}

diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
index 69a8626a35c0..c2f2ad34f9b7 100644
--- a/security/integrity/ima/ima_queue_keys.c
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -162,7 +162,8 @@ void ima_process_queued_keys(void)
entry->payload_len,
entry->keyring_name,
KEY_CHECK, 0,
- entry->keyring_name);
+ entry->keyring_name,
+ false);
list_del(&entry->list);
ima_free_key_entry(entry);
}
--
2.17.1