[PATCH 7/8] ima: use ima_hash_algo for collision detection in the measurement list

Roberto Sassu
2020-01-27T17:07:17Z

Before calculating a digest for each PCR bank, collisions were detected
with a SHA1 digest. This patch includes ima_hash_algo among the algorithms
used to calculate the template digest and checks collisions on that digest.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_api.c | 2 +-
security/integrity/ima/ima_crypto.c | 25 ++++++++++++++++++-------
security/integrity/ima/ima_main.c | 1 +
security/integrity/ima/ima_queue.c | 8 ++++----
security/integrity/ima/ima_template.c | 2 +-
6 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index d959dab5bcce..3e1afa5150bc 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -51,6 +51,7 @@ extern int ima_policy_flag;
/* set during initialization */
extern int ima_hash_algo;
extern int ima_sha1_idx;
+extern int ima_hash_algo_idx;
extern int ima_appraise;
extern struct tpm_chip *ima_tpm_chip;

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index ebaf0056735c..a9bb45de6db9 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -51,7 +51,7 @@ int ima_alloc_init_template(struct ima_event_data *event_data,
if (!*entry)
return -ENOMEM;

- (*entry)->digests = kcalloc(ima_tpm_chip->nr_allocated_banks + 1,
+ (*entry)->digests = kcalloc(ima_tpm_chip->nr_allocated_banks + 2,
sizeof(*(*entry)->digests), GFP_NOFS);
if (!(*entry)->digests) {
result = -ENOMEM;
diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index 786340feebbb..f84dfd8fc5ca 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -93,7 +93,7 @@ static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
if (algo == ima_hash_algo)
return tfm;

- for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 1; i++)
+ for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 2; i++)
if (ima_algo_array[i].algo == algo && ima_algo_array[i].tfm)
return ima_algo_array[i].tfm;

@@ -116,19 +116,20 @@ int __init ima_init_crypto(void)
if (rc)
return rc;

- ima_algo_array = kmalloc_array(ima_tpm_chip->nr_allocated_banks + 1,
+ ima_algo_array = kmalloc_array(ima_tpm_chip->nr_allocated_banks + 2,
sizeof(*ima_algo_array), GFP_KERNEL);
if (!ima_algo_array) {
rc = -ENOMEM;
goto out;
}

- for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 1; i++) {
+ for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 2; i++) {
ima_algo_array[i].tfm = NULL;
ima_algo_array[i].algo = HASH_ALGO__LAST;
}

ima_sha1_idx = -1;
+ ima_hash_algo_idx = -1;

for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) {
algo = ima_tpm_chip->allocated_banks[i].crypto_id;
@@ -143,6 +144,7 @@ int __init ima_init_crypto(void)

if (algo == ima_hash_algo) {
ima_algo_array[i].tfm = ima_shash_tfm;
+ ima_hash_algo_idx = i;
continue;
}

@@ -166,12 +168,21 @@ int __init ima_init_crypto(void)
}

ima_sha1_idx = i;
- ima_algo_array[i].algo = HASH_ALGO_SHA1;
+ if (ima_hash_algo == HASH_ALGO_SHA1)
+ ima_hash_algo_idx = i;
+
+ ima_algo_array[i++].algo = HASH_ALGO_SHA1;
+ }
+
+ if (ima_hash_algo_idx < 0) {
+ ima_algo_array[i].tfm = ima_shash_tfm;
+ ima_algo_array[i].algo = ima_hash_algo;
+ ima_hash_algo_idx = i;
}

return 0;
out_array:
- for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 1; i++) {
+ for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 2; i++) {
if (!ima_algo_array[i].tfm ||
ima_algo_array[i].tfm == ima_shash_tfm)
continue;
@@ -190,7 +201,7 @@ static void ima_free_tfm(struct crypto_shash *tfm)
if (tfm == ima_shash_tfm)
return;

- for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 1; i++)
+ for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 2; i++)
if (ima_algo_array[i].tfm == tfm)
return;

@@ -619,7 +630,7 @@ int ima_calc_field_array_hash(struct ima_field_data *field_data,

entry->digests[ima_sha1_idx].alg_id = TPM_ALG_SHA1;

- for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 1; i++) {
+ for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 2; i++) {
if (i == ima_sha1_idx)
continue;

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index c068067a0c47..6963d6c31bf1 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -31,6 +31,7 @@
#include "ima.h"

int ima_sha1_idx;
+int ima_hash_algo_idx;

#ifdef CONFIG_IMA_APPRAISE
int ima_appraise = IMA_APPRAISE_ENFORCE;
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 7f7509774b85..58983d0f0214 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -57,8 +57,8 @@ static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
key = ima_hash_key(digest_value);
rcu_read_lock();
hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
- rc = memcmp(qe->entry->digests[ima_sha1_idx].digest,
- digest_value, TPM_DIGEST_SIZE);
+ rc = memcmp(qe->entry->digests[ima_hash_algo_idx].digest,
+ digest_value, hash_digest_size[ima_hash_algo]);
if ((rc == 0) && (qe->entry->pcr == pcr)) {
ret = qe;
break;
@@ -110,7 +110,7 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,

atomic_long_inc(&ima_htable.len);
if (update_htable) {
- key = ima_hash_key(entry->digests[ima_sha1_idx].digest);
+ key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
}

@@ -162,7 +162,7 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
const char *op, struct inode *inode,
const unsigned char *filename)
{
- u8 *digest = entry->digests[ima_sha1_idx].digest;
+ u8 *digest = entry->digests[ima_hash_algo_idx].digest;
struct tpm_digest *digests_arg = entry->digests;
const char *audit_cause = "hash_added";
char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index a9e1390c8e12..f71b5ee44179 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -311,7 +311,7 @@ static int ima_restore_template_data(struct ima_template_desc *template_desc,
if (!*entry)
return -ENOMEM;

- (*entry)->digests = kcalloc(ima_tpm_chip->nr_allocated_banks + 1,
+ (*entry)->digests = kcalloc(ima_tpm_chip->nr_allocated_banks + 2,
sizeof(*(*entry)->digests), GFP_NOFS);
if (!(*entry)->digests) {
kfree(*entry);
--
2.17.1