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-rw-r--r--security/integrity/evm/evm.h9
-rw-r--r--security/integrity/evm/evm_crypto.c75
-rw-r--r--security/integrity/evm/evm_main.c67
-rw-r--r--security/integrity/evm/evm_secfs.c20
4 files changed, 139 insertions, 32 deletions
diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index 241aca315b0c..04825393facb 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -23,9 +23,12 @@
#define EVM_INIT_HMAC 0x0001
#define EVM_INIT_X509 0x0002
-#define EVM_SETUP 0x80000000 /* userland has signaled key load */
+#define EVM_ALLOW_METADATA_WRITES 0x0004
+#define EVM_SETUP_COMPLETE 0x80000000 /* userland has signaled key load */
-#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP)
+#define EVM_KEY_MASK (EVM_INIT_HMAC | EVM_INIT_X509)
+#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE | \
+ EVM_ALLOW_METADATA_WRITES)
extern int evm_initialized;
extern char *evm_hmac;
@@ -51,7 +54,7 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
size_t req_xattr_value_len, char *digest);
int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value,
- size_t req_xattr_value_len, char *digest);
+ size_t req_xattr_value_len, char type, char *digest);
int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
char *hmac_val);
int evm_init_secfs(void);
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index bcd64baf8788..691f3e09154c 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -138,7 +138,7 @@ out:
* protection.)
*/
static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
- char *digest)
+ char type, char *digest)
{
struct h_misc {
unsigned long ino;
@@ -149,8 +149,13 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
} hmac_misc;
memset(&hmac_misc, 0, sizeof(hmac_misc));
- hmac_misc.ino = inode->i_ino;
- hmac_misc.generation = inode->i_generation;
+ /* Don't include the inode or generation number in portable
+ * signatures
+ */
+ if (type != EVM_XATTR_PORTABLE_DIGSIG) {
+ hmac_misc.ino = inode->i_ino;
+ hmac_misc.generation = inode->i_generation;
+ }
/* The hmac uid and gid must be encoded in the initial user
* namespace (not the filesystems user namespace) as encoding
* them in the filesystems user namespace allows an attack
@@ -163,7 +168,8 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid);
hmac_misc.mode = inode->i_mode;
crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc));
- if (evm_hmac_attrs & EVM_ATTR_FSUUID)
+ if ((evm_hmac_attrs & EVM_ATTR_FSUUID) &&
+ type != EVM_XATTR_PORTABLE_DIGSIG)
crypto_shash_update(desc, &inode->i_sb->s_uuid.b[0],
sizeof(inode->i_sb->s_uuid));
crypto_shash_final(desc, digest);
@@ -189,6 +195,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
char *xattr_value = NULL;
int error;
int size;
+ bool ima_present = false;
if (!(inode->i_opflags & IOP_XATTR))
return -EOPNOTSUPP;
@@ -199,11 +206,18 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
error = -ENODATA;
for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
+ bool is_ima = false;
+
+ if (strcmp(*xattrname, XATTR_NAME_IMA) == 0)
+ is_ima = true;
+
if ((req_xattr_name && req_xattr_value)
&& !strcmp(*xattrname, req_xattr_name)) {
error = 0;
crypto_shash_update(desc, (const u8 *)req_xattr_value,
req_xattr_value_len);
+ if (is_ima)
+ ima_present = true;
continue;
}
size = vfs_getxattr_alloc(dentry, *xattrname,
@@ -218,9 +232,14 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
error = 0;
xattr_size = size;
crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
+ if (is_ima)
+ ima_present = true;
}
- hmac_add_misc(desc, inode, digest);
+ hmac_add_misc(desc, inode, type, digest);
+ /* Portable EVM signatures must include an IMA hash */
+ if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present)
+ return -EPERM;
out:
kfree(xattr_value);
kfree(desc);
@@ -232,17 +251,45 @@ int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
char *digest)
{
return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
- req_xattr_value_len, EVM_XATTR_HMAC, digest);
+ req_xattr_value_len, EVM_XATTR_HMAC, digest);
}
int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
const char *req_xattr_value, size_t req_xattr_value_len,
- char *digest)
+ char type, char *digest)
{
return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value,
- req_xattr_value_len, IMA_XATTR_DIGEST, digest);
+ req_xattr_value_len, type, digest);
+}
+
+static int evm_is_immutable(struct dentry *dentry, struct inode *inode)
+{
+ const struct evm_ima_xattr_data *xattr_data = NULL;
+ struct integrity_iint_cache *iint;
+ int rc = 0;
+
+ iint = integrity_iint_find(inode);
+ if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG))
+ return 1;
+
+ /* Do this the hard way */
+ rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
+ GFP_NOFS);
+ if (rc <= 0) {
+ if (rc == -ENODATA)
+ return 0;
+ return rc;
+ }
+ if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG)
+ rc = 1;
+ else
+ rc = 0;
+
+ kfree(xattr_data);
+ return rc;
}
+
/*
* Calculate the hmac and update security.evm xattr
*
@@ -255,6 +302,16 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
struct evm_ima_xattr_data xattr_data;
int rc = 0;
+ /*
+ * Don't permit any transformation of the EVM xattr if the signature
+ * is of an immutable type
+ */
+ rc = evm_is_immutable(dentry, inode);
+ if (rc < 0)
+ return rc;
+ if (rc)
+ return -EPERM;
+
rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
xattr_value_len, xattr_data.digest);
if (rc == 0) {
@@ -280,7 +337,7 @@ int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr,
}
crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len);
- hmac_add_misc(desc, inode, hmac_val);
+ hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val);
kfree(desc);
return 0;
}
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 9826c02e2db8..a8d502827270 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -31,7 +31,7 @@
int evm_initialized;
static char *integrity_status_msg[] = {
- "pass", "fail", "no_label", "no_xattrs", "unknown"
+ "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
};
char *evm_hmac = "hmac(sha1)";
char *evm_hash = "sha1";
@@ -76,6 +76,11 @@ static void __init evm_init_config(void)
pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
}
+static bool evm_key_loaded(void)
+{
+ return (bool)(evm_initialized & EVM_KEY_MASK);
+}
+
static int evm_find_protected_xattrs(struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
@@ -123,7 +128,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
enum integrity_status evm_status = INTEGRITY_PASS;
int rc, xattr_len;
- if (iint && iint->evm_status == INTEGRITY_PASS)
+ if (iint && (iint->evm_status == INTEGRITY_PASS ||
+ iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
return iint->evm_status;
/* if status is not PASS, try to check again - against -ENOMEM */
@@ -164,22 +170,26 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
rc = -EINVAL;
break;
case EVM_IMA_XATTR_DIGSIG:
+ case EVM_XATTR_PORTABLE_DIGSIG:
rc = evm_calc_hash(dentry, xattr_name, xattr_value,
- xattr_value_len, calc.digest);
+ xattr_value_len, xattr_data->type,
+ calc.digest);
if (rc)
break;
rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
(const char *)xattr_data, xattr_len,
calc.digest, sizeof(calc.digest));
if (!rc) {
- /* Replace RSA with HMAC if not mounted readonly and
- * not immutable
- */
- if (!IS_RDONLY(d_backing_inode(dentry)) &&
- !IS_IMMUTABLE(d_backing_inode(dentry)))
+ if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
+ if (iint)
+ iint->flags |= EVM_IMMUTABLE_DIGSIG;
+ evm_status = INTEGRITY_PASS_IMMUTABLE;
+ } else if (!IS_RDONLY(d_backing_inode(dentry)) &&
+ !IS_IMMUTABLE(d_backing_inode(dentry))) {
evm_update_evmxattr(dentry, xattr_name,
xattr_value,
xattr_value_len);
+ }
}
break;
default:
@@ -241,7 +251,7 @@ enum integrity_status evm_verifyxattr(struct dentry *dentry,
void *xattr_value, size_t xattr_value_len,
struct integrity_iint_cache *iint)
{
- if (!evm_initialized || !evm_protected_xattr(xattr_name))
+ if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
return INTEGRITY_UNKNOWN;
if (!iint) {
@@ -265,7 +275,7 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
{
struct inode *inode = d_backing_inode(dentry);
- if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
+ if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
return 0;
return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
}
@@ -280,7 +290,7 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
* affect security.evm. An interesting side affect of writing posix xattr
* acls is their modifying of the i_mode, which is included in security.evm.
* For posix xattr acls only, permit security.evm, even if it currently
- * doesn't exist, to be updated.
+ * doesn't exist, to be updated unless the EVM signature is immutable.
*/
static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
@@ -299,6 +309,7 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
return 0;
goto out;
}
+
evm_status = evm_verify_current_integrity(dentry);
if (evm_status == INTEGRITY_NOXATTRS) {
struct integrity_iint_cache *iint;
@@ -345,10 +356,17 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
{
const struct evm_ima_xattr_data *xattr_data = xattr_value;
+ /* Policy permits modification of the protected xattrs even though
+ * there's no HMAC key loaded
+ */
+ if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+ return 0;
+
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
if (!xattr_value_len)
return -EINVAL;
- if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
+ if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
+ xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
return -EPERM;
}
return evm_protect_xattr(dentry, xattr_name, xattr_value,
@@ -365,6 +383,12 @@ int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
*/
int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
{
+ /* Policy permits modification of the protected xattrs even though
+ * there's no HMAC key loaded
+ */
+ if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+ return 0;
+
return evm_protect_xattr(dentry, xattr_name, NULL, 0);
}
@@ -393,8 +417,8 @@ static void evm_reset_status(struct inode *inode)
void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
- if (!evm_initialized || (!evm_protected_xattr(xattr_name)
- && !posix_xattr_acl(xattr_name)))
+ if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name)
+ && !posix_xattr_acl(xattr_name)))
return;
evm_reset_status(dentry->d_inode);
@@ -414,7 +438,7 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
*/
void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
{
- if (!evm_initialized || !evm_protected_xattr(xattr_name))
+ if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
return;
evm_reset_status(dentry->d_inode);
@@ -425,12 +449,21 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
/**
* evm_inode_setattr - prevent updating an invalid EVM extended attribute
* @dentry: pointer to the affected dentry
+ *
+ * Permit update of file attributes when files have a valid EVM signature,
+ * except in the case of them having an immutable portable signature.
*/
int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
{
unsigned int ia_valid = attr->ia_valid;
enum integrity_status evm_status;
+ /* Policy permits modification of the protected attrs even though
+ * there's no HMAC key loaded
+ */
+ if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
+ return 0;
+
if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
return 0;
evm_status = evm_verify_current_integrity(dentry);
@@ -456,7 +489,7 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
*/
void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
{
- if (!evm_initialized)
+ if (!evm_key_loaded())
return;
if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
@@ -473,7 +506,7 @@ int evm_inode_init_security(struct inode *inode,
struct evm_ima_xattr_data *xattr_data;
int rc;
- if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
+ if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
return 0;
xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index 319cf16d6603..feba03bbedae 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -40,7 +40,7 @@ static ssize_t evm_read_key(struct file *filp, char __user *buf,
if (*ppos != 0)
return 0;
- sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP));
+ sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE));
rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
return rc;
@@ -63,7 +63,7 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf,
{
int i, ret;
- if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP))
+ if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE))
return -EPERM;
ret = kstrtoint_from_user(buf, count, 0, &i);
@@ -75,16 +75,30 @@ static ssize_t evm_write_key(struct file *file, const char __user *buf,
if (!i || (i & ~EVM_INIT_MASK) != 0)
return -EINVAL;
+ /* Don't allow a request to freshly enable metadata writes if
+ * keys are loaded.
+ */
+ if ((i & EVM_ALLOW_METADATA_WRITES) &&
+ ((evm_initialized & EVM_KEY_MASK) != 0) &&
+ !(evm_initialized & EVM_ALLOW_METADATA_WRITES))
+ return -EPERM;
+
if (i & EVM_INIT_HMAC) {
ret = evm_init_key();
if (ret != 0)
return ret;
/* Forbid further writes after the symmetric key is loaded */
- i |= EVM_SETUP;
+ i |= EVM_SETUP_COMPLETE;
}
evm_initialized |= i;
+ /* Don't allow protected metadata modification if a symmetric key
+ * is loaded
+ */
+ if (evm_initialized & EVM_INIT_HMAC)
+ evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES);
+
return count;
}
generated by cgit v1.2.3-55-g7522 (git 2.39.0) at 2024-07-17 10:01:26 +0200