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ima: Use ima_hash_algo for collision detection in the measurement list 

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.

The position in the measurement entry array of the template digest
calculated with the IMA default hash algorithm is stored in the
ima_hash_algo_idx global variable and is determined at IMA initialization
time.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Roberto Sassu 2020-03-25 11:54:24 +01:00 committed by Mimi Zohar
parent 1ea973df6e
commit 2592677c04
3 changed files with 23 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
security/integrity/ima/ima.h
View File

@ -53,6 +53,7 @@ extern int ima_policy_flag;
/* set during initialization */
extern int ima_hash_algo;
extern int ima_sha1_idx __ro_after_init;
extern int ima_hash_algo_idx __ro_after_init;
extern int ima_extra_slots __ro_after_init;
extern int ima_appraise;
extern struct tpm_chip *ima_tpm_chip;

19
security/integrity/ima/ima_crypto.c
View File

@ -63,6 +63,7 @@ struct ima_algo_desc {
};
int ima_sha1_idx __ro_after_init;
int ima_hash_algo_idx __ro_after_init;
/*
* Additional number of slots reserved, as needed, for SHA1
* and IMA default algo.
@ -122,15 +123,25 @@ int __init ima_init_crypto(void)
return rc;
ima_sha1_idx = -1;
ima_hash_algo_idx = -1;
for (i = 0; i < NR_BANKS(ima_tpm_chip); i++) {
algo = ima_tpm_chip->allocated_banks[i].crypto_id;
if (algo == HASH_ALGO_SHA1)
ima_sha1_idx = i;
if (algo == ima_hash_algo)
ima_hash_algo_idx = i;
}
if (ima_sha1_idx < 0)
if (ima_sha1_idx < 0) {
ima_sha1_idx = NR_BANKS(ima_tpm_chip) + ima_extra_slots++;
if (ima_hash_algo == HASH_ALGO_SHA1)
ima_hash_algo_idx = ima_sha1_idx;
}
if (ima_hash_algo_idx < 0)
ima_hash_algo_idx = NR_BANKS(ima_tpm_chip) + ima_extra_slots++;
ima_algo_array = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
sizeof(*ima_algo_array), GFP_KERNEL);
@ -179,6 +190,12 @@ int __init ima_init_crypto(void)
ima_algo_array[ima_sha1_idx].algo = HASH_ALGO_SHA1;
}
if (ima_hash_algo_idx >= NR_BANKS(ima_tpm_chip) &&
ima_hash_algo_idx != ima_sha1_idx) {
ima_algo_array[ima_hash_algo_idx].tfm = ima_shash_tfm;
ima_algo_array[ima_hash_algo_idx].algo = ima_hash_algo;
}
return 0;
out_array:
for (i = 0; i < NR_BANKS(ima_tpm_chip) + ima_extra_slots; i++) {

8
security/integrity/ima/ima_queue.c
View File

@ -55,8 +55,8 @@ 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;
@ -108,7 +108,7 @@ 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]);
}
@ -160,7 +160,7 @@ 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];