integrity: Introduce struct evm_xattr

Even though struct evm_ima_xattr_data includes a fixed-size array to hold a
SHA1 digest, most of the code ignores the array and uses the struct to mean
"type indicator followed by data of unspecified size" and tracks the real
size of what the struct represents in a separate length variable.

The only exception to that is the EVM code, which correctly uses the
definition of struct evm_ima_xattr_data.

So make this explicit in the code by removing the length specification from
the array in struct evm_ima_xattr_data. Also, change the name of the
element from digest to data since in most places the array doesn't hold a
digest.

A separate struct evm_xattr is introduced, with the original definition of
evm_ima_xattr_data to be used in the places that actually expect that
definition, specifically the EVM HMAC code.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index b6d9f14bc23477caa2f735172a89e6a059d1194d..588f22f1b5bdcc9c5550791c4fce8828ea356e51 100644 (file)
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -169,7 +169,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
        /* check value type */
        switch (xattr_data->type) {
        case EVM_XATTR_HMAC:
-               if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
+               if (xattr_len != sizeof(struct evm_xattr)) {
                        evm_status = INTEGRITY_FAIL;
                        goto out;
                }
@@ -179,7 +179,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
                                   xattr_value_len, &digest);
                if (rc)
                        break;
-               rc = crypto_memneq(xattr_data->digest, digest.digest,
+               rc = crypto_memneq(xattr_data->data, digest.digest,
                                   SHA1_DIGEST_SIZE);
                if (rc)
                        rc = -EINVAL;
@@ -523,7 +523,7 @@ int evm_inode_init_security(struct inode *inode,
                                 const struct xattr *lsm_xattr,
                                 struct xattr *evm_xattr)
 {
-       struct evm_ima_xattr_data *xattr_data;
+       struct evm_xattr *xattr_data;
        int rc;
 
        if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
@@ -533,7 +533,7 @@ int evm_inode_init_security(struct inode *inode,
        if (!xattr_data)
                return -ENOMEM;
 
-       xattr_data->type = EVM_XATTR_HMAC;
+       xattr_data->data.type = EVM_XATTR_HMAC;
        rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
        if (rc < 0)
                goto out;

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 2f6536ab69e899f4c6e514892da5b53fd26b1f7c..18bbe753421a57e7d5912efe348d8811fd21000b 100644 (file)
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -168,7 +168,8 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
                return sig->hash_algo;
                break;
        case IMA_XATTR_DIGEST_NG:
-               ret = xattr_value->digest[0];
+               /* first byte contains algorithm id */
+               ret = xattr_value->data[0];
                if (ret < HASH_ALGO__LAST)
                        return ret;
                break;
@@ -176,7 +177,7 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
                /* this is for backward compatibility */
                if (xattr_len == 21) {
                        unsigned int zero = 0;
-                       if (!memcmp(&xattr_value->digest[16], &zero, 4))
+                       if (!memcmp(&xattr_value->data[16], &zero, 4))
                                return HASH_ALGO_MD5;
                        else
                                return HASH_ALGO_SHA1;
@@ -275,7 +276,7 @@ int ima_appraise_measurement(enum ima_hooks func,
                        /* xattr length may be longer. md5 hash in previous
                           version occupied 20 bytes in xattr, instead of 16
                         */
-                       rc = memcmp(&xattr_value->digest[hash_start],
+                       rc = memcmp(&xattr_value->data[hash_start],
                                    iint->ima_hash->digest,
                                    iint->ima_hash->length);
                else

diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 7de59f44cba3b3f9d32d15d864c1b5e8fe0861ac..88a29f72a74fb5472c84e070acd121f66f785e1d 100644 (file)
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -79,6 +79,12 @@ enum evm_ima_xattr_type {
 
 struct evm_ima_xattr_data {
        u8 type;
+       u8 data[];
+} __packed;
+
+/* Only used in the EVM HMAC code. */
+struct evm_xattr {
+       struct evm_ima_xattr_data data;
        u8 digest[SHA1_DIGEST_SIZE];
 } __packed;