Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 466 insertions, 0 deletions

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
new file mode 100644
index 000000000..deec1804a
--- /dev/null
+++ b/security/integrity/ima/ima_appraise.c
@@ -0,0 +1,466 @@
+/*
+ * Copyright (C) 2011 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ */
+#include <linux/module.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/xattr.h>
+#include <linux/magic.h>
+#include <linux/ima.h>
+#include <linux/evm.h>
+
+#include "ima.h"
+
+static int __init default_appraise_setup(char *str)
+{
+#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
+	if (strncmp(str, "off", 3) == 0)
+		ima_appraise = 0;
+	else if (strncmp(str, "log", 3) == 0)
+		ima_appraise = IMA_APPRAISE_LOG;
+	else if (strncmp(str, "fix", 3) == 0)
+		ima_appraise = IMA_APPRAISE_FIX;
+#endif
+	return 1;
+}
+
+__setup("ima_appraise=", default_appraise_setup);
+
+/*
+ * is_ima_appraise_enabled - return appraise status
+ *
+ * Only return enabled, if not in ima_appraise="fix" or "log" modes.
+ */
+bool is_ima_appraise_enabled(void)
+{
+	return ima_appraise & IMA_APPRAISE_ENFORCE;
+}
+
+/*
+ * ima_must_appraise - set appraise flag
+ *
+ * Return 1 to appraise or hash
+ */
+int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
+{
+	u32 secid;
+
+	if (!ima_appraise)
+		return 0;
+
+	security_task_getsecid(current, &secid);
+	return ima_match_policy(inode, current_cred(), secid, func, mask,
+				IMA_APPRAISE | IMA_HASH, NULL);
+}
+
+static int ima_fix_xattr(struct dentry *dentry,
+			 struct integrity_iint_cache *iint)
+{
+	int rc, offset;
+	u8 algo = iint->ima_hash->algo;
+
+	if (algo <= HASH_ALGO_SHA1) {
+		offset = 1;
+		iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
+	} else {
+		offset = 0;
+		iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
+		iint->ima_hash->xattr.ng.algo = algo;
+	}
+	rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA,
+				   &iint->ima_hash->xattr.data[offset],
+				   (sizeof(iint->ima_hash->xattr) - offset) +
+				   iint->ima_hash->length, 0);
+	return rc;
+}
+
+/* Return specific func appraised cached result */
+enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
+					   enum ima_hooks func)
+{
+	switch (func) {
+	case MMAP_CHECK:
+		return iint->ima_mmap_status;
+	case BPRM_CHECK:
+		return iint->ima_bprm_status;
+	case CREDS_CHECK:
+		return iint->ima_creds_status;
+	case FILE_CHECK:
+	case POST_SETATTR:
+		return iint->ima_file_status;
+	case MODULE_CHECK ... MAX_CHECK - 1:
+	default:
+		return iint->ima_read_status;
+	}
+}
+
+static void ima_set_cache_status(struct integrity_iint_cache *iint,
+				 enum ima_hooks func,
+				 enum integrity_status status)
+{
+	switch (func) {
+	case MMAP_CHECK:
+		iint->ima_mmap_status = status;
+		break;
+	case BPRM_CHECK:
+		iint->ima_bprm_status = status;
+		break;
+	case CREDS_CHECK:
+		iint->ima_creds_status = status;
+	case FILE_CHECK:
+	case POST_SETATTR:
+		iint->ima_file_status = status;
+		break;
+	case MODULE_CHECK ... MAX_CHECK - 1:
+	default:
+		iint->ima_read_status = status;
+		break;
+	}
+}
+
+static void ima_cache_flags(struct integrity_iint_cache *iint,
+			     enum ima_hooks func)
+{
+	switch (func) {
+	case MMAP_CHECK:
+		iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
+		break;
+	case BPRM_CHECK:
+		iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
+		break;
+	case CREDS_CHECK:
+		iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
+		break;
+	case FILE_CHECK:
+	case POST_SETATTR:
+		iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
+		break;
+	case MODULE_CHECK ... MAX_CHECK - 1:
+	default:
+		iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
+		break;
+	}
+}
+
+enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
+				 int xattr_len)
+{
+	struct signature_v2_hdr *sig;
+	enum hash_algo ret;
+
+	if (!xattr_value || xattr_len < 2)
+		/* return default hash algo */
+		return ima_hash_algo;
+
+	switch (xattr_value->type) {
+	case EVM_IMA_XATTR_DIGSIG:
+		sig = (typeof(sig))xattr_value;
+		if (sig->version != 2 || xattr_len <= sizeof(*sig))
+			return ima_hash_algo;
+		return sig->hash_algo;
+		break;
+	case IMA_XATTR_DIGEST_NG:
+		ret = xattr_value->digest[0];
+		if (ret < HASH_ALGO__LAST)
+			return ret;
+		break;
+	case IMA_XATTR_DIGEST:
+		/* this is for backward compatibility */
+		if (xattr_len == 21) {
+			unsigned int zero = 0;
+			if (!memcmp(&xattr_value->digest[16], &zero, 4))
+				return HASH_ALGO_MD5;
+			else
+				return HASH_ALGO_SHA1;
+		} else if (xattr_len == 17)
+			return HASH_ALGO_MD5;
+		break;
+	}
+
+	/* return default hash algo */
+	return ima_hash_algo;
+}
+
+int ima_read_xattr(struct dentry *dentry,
+		   struct evm_ima_xattr_data **xattr_value)
+{
+	ssize_t ret;
+
+	ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
+				 0, GFP_NOFS);
+	if (ret == -EOPNOTSUPP)
+		ret = 0;
+	return ret;
+}
+
+/*
+ * ima_appraise_measurement - appraise file measurement
+ *
+ * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
+ * Assuming success, compare the xattr hash with the collected measurement.
+ *
+ * Return 0 on success, error code otherwise
+ */
+int ima_appraise_measurement(enum ima_hooks func,
+			     struct integrity_iint_cache *iint,
+			     struct file *file, const unsigned char *filename,
+			     struct evm_ima_xattr_data *xattr_value,
+			     int xattr_len)
+{
+	static const char op[] = "appraise_data";
+	const char *cause = "unknown";
+	struct dentry *dentry = file_dentry(file);
+	struct inode *inode = d_backing_inode(dentry);
+	enum integrity_status status = INTEGRITY_UNKNOWN;
+	int rc = xattr_len, hash_start = 0;
+
+	if (!(inode->i_opflags & IOP_XATTR))
+		return INTEGRITY_UNKNOWN;
+
+	if (rc <= 0) {
+		if (rc && rc != -ENODATA)
+			goto out;
+
+		cause = iint->flags & IMA_DIGSIG_REQUIRED ?
+				"IMA-signature-required" : "missing-hash";
+		status = INTEGRITY_NOLABEL;
+		if (file->f_mode & FMODE_CREATED)
+			iint->flags |= IMA_NEW_FILE;
+		if ((iint->flags & IMA_NEW_FILE) &&
+		    (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
+		     (inode->i_size == 0)))
+			status = INTEGRITY_PASS;
+		goto out;
+	}
+
+	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
+	switch (status) {
+	case INTEGRITY_PASS:
+	case INTEGRITY_PASS_IMMUTABLE:
+	case INTEGRITY_UNKNOWN:
+		break;
+	case INTEGRITY_NOXATTRS:	/* No EVM protected xattrs. */
+	case INTEGRITY_NOLABEL:		/* No security.evm xattr. */
+		cause = "missing-HMAC";
+		goto out;
+	case INTEGRITY_FAIL:		/* Invalid HMAC/signature. */
+		cause = "invalid-HMAC";
+		goto out;
+	default:
+		WARN_ONCE(true, "Unexpected integrity status %d\n", status);
+	}
+
+	switch (xattr_value->type) {
+	case IMA_XATTR_DIGEST_NG:
+		/* first byte contains algorithm id */
+		hash_start = 1;
+		/* fall through */
+	case IMA_XATTR_DIGEST:
+		if (iint->flags & IMA_DIGSIG_REQUIRED) {
+			cause = "IMA-signature-required";
+			status = INTEGRITY_FAIL;
+			break;
+		}
+		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
+		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
+				iint->ima_hash->length)
+			/* 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],
+				    iint->ima_hash->digest,
+				    iint->ima_hash->length);
+		else
+			rc = -EINVAL;
+		if (rc) {
+			cause = "invalid-hash";
+			status = INTEGRITY_FAIL;
+			break;
+		}
+		status = INTEGRITY_PASS;
+		break;
+	case EVM_IMA_XATTR_DIGSIG:
+		set_bit(IMA_DIGSIG, &iint->atomic_flags);
+		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
+					     (const char *)xattr_value, rc,
+					     iint->ima_hash->digest,
+					     iint->ima_hash->length);
+		if (rc == -EOPNOTSUPP) {
+			status = INTEGRITY_UNKNOWN;
+		} else if (rc) {
+			cause = "invalid-signature";
+			status = INTEGRITY_FAIL;
+		} else {
+			status = INTEGRITY_PASS;
+		}
+		break;
+	default:
+		status = INTEGRITY_UNKNOWN;
+		cause = "unknown-ima-data";
+		break;
+	}
+
+out:
+	/*
+	 * File signatures on some filesystems can not be properly verified.
+	 * When such filesystems are mounted by an untrusted mounter or on a
+	 * system not willing to accept such a risk, fail the file signature
+	 * verification.
+	 */
+	if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
+	    ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
+	     (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
+		status = INTEGRITY_FAIL;
+		cause = "unverifiable-signature";
+		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
+				    op, cause, rc, 0);
+	} else if (status != INTEGRITY_PASS) {
+		/* Fix mode, but don't replace file signatures. */
+		if ((ima_appraise & IMA_APPRAISE_FIX) &&
+		    (!xattr_value ||
+		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
+			if (!ima_fix_xattr(dentry, iint))
+				status = INTEGRITY_PASS;
+		}
+
+		/* Permit new files with file signatures, but without data. */
+		if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
+		    xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) {
+			status = INTEGRITY_PASS;
+		}
+
+		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
+				    op, cause, rc, 0);
+	} else {
+		ima_cache_flags(iint, func);
+	}
+
+	ima_set_cache_status(iint, func, status);
+	return status;
+}
+
+/*
+ * ima_update_xattr - update 'security.ima' hash value
+ */
+void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
+{
+	struct dentry *dentry = file_dentry(file);
+	int rc = 0;
+
+	/* do not collect and update hash for digital signatures */
+	if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
+		return;
+
+	if ((iint->ima_file_status != INTEGRITY_PASS) &&
+	    !(iint->flags & IMA_HASH))
+		return;
+
+	rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
+	if (rc < 0)
+		return;
+
+	inode_lock(file_inode(file));
+	ima_fix_xattr(dentry, iint);
+	inode_unlock(file_inode(file));
+}
+
+/**
+ * ima_inode_post_setattr - reflect file metadata changes
+ * @dentry: pointer to the affected dentry
+ *
+ * Changes to a dentry's metadata might result in needing to appraise.
+ *
+ * This function is called from notify_change(), which expects the caller
+ * to lock the inode's i_mutex.
+ */
+void ima_inode_post_setattr(struct dentry *dentry)
+{
+	struct inode *inode = d_backing_inode(dentry);
+	struct integrity_iint_cache *iint;
+	int action;
+
+	if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
+	    || !(inode->i_opflags & IOP_XATTR))
+		return;
+
+	action = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR);
+	if (!action)
+		__vfs_removexattr(dentry, XATTR_NAME_IMA);
+	iint = integrity_iint_find(inode);
+	if (iint) {
+		set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags);
+		if (!action)
+			clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
+	}
+}
+
+/*
+ * ima_protect_xattr - protect 'security.ima'
+ *
+ * Ensure that not just anyone can modify or remove 'security.ima'.
+ */
+static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
+			     const void *xattr_value, size_t xattr_value_len)
+{
+	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		return 1;
+	}
+	return 0;
+}
+
+static void ima_reset_appraise_flags(struct inode *inode, int digsig)
+{
+	struct integrity_iint_cache *iint;
+
+	if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
+		return;
+
+	iint = integrity_iint_find(inode);
+	if (!iint)
+		return;
+	iint->measured_pcrs = 0;
+	set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
+	if (digsig)
+		set_bit(IMA_DIGSIG, &iint->atomic_flags);
+	else
+		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
+}
+
+int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
+		       const void *xattr_value, size_t xattr_value_len)
+{
+	const struct evm_ima_xattr_data *xvalue = xattr_value;
+	int result;
+
+	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
+				   xattr_value_len);
+	if (result == 1) {
+		if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
+			return -EINVAL;
+		ima_reset_appraise_flags(d_backing_inode(dentry),
+			xvalue->type == EVM_IMA_XATTR_DIGSIG);
+		result = 0;
+	}
+	return result;
+}
+
+int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
+{
+	int result;
+
+	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
+	if (result == 1) {
+		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
+		result = 0;
+	}
+	return result;
+}