[RFC PATCH v7 13/16] ipe: enable support for fs-verity as a trust provider

deven.desai
2021-10-13T19:07:20Z

From: Fan Wu <wufan@linux.microsoft.com>

Enable IPE policy authors to indicate trust for a singular fsverity
file, identified by the digest information, through "fsverity_digest"
and all fsverity signed by a key via "fsverity_signature".

Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
---

Relevant changes since v6:
* Add FSVerity Support (Introduced)

---
security/ipe/eval.c | 1 +
security/ipe/eval.h | 9 +++
security/ipe/hooks.c | 58 ++++++++++++++++
security/ipe/hooks.h | 7 ++
security/ipe/ipe.c | 8 +++
security/ipe/ipe.h | 1 +
security/ipe/modules/Kconfig | 23 +++++++
security/ipe/modules/Makefile | 2 +
security/ipe/modules/fsverity_digest.c | 80 +++++++++++++++++++++++
security/ipe/modules/fsverity_signature.c | 33 ++++++++++
10 files changed, 222 insertions(+)
create mode 100644 security/ipe/modules/fsverity_digest.c
create mode 100644 security/ipe/modules/fsverity_signature.c

diff --git a/security/ipe/eval.c b/security/ipe/eval.c
index facc05c753f4..8f8b91c714c2 100644
--- a/security/ipe/eval.c
+++ b/security/ipe/eval.c
@@ -97,6 +97,7 @@ static struct ipe_eval_ctx *build_ctx(const struct file *file,
ctx->ci_ctx = ipe_current_ctx();
ctx->from_init_sb = from_pinned(file);
if (file) {
+ ctx->ipe_inode = ipe_inode(file->f_inode);
if (FILE_BLOCK_DEV(file))
ctx->ipe_bdev = ipe_bdev(FILE_BLOCK_DEV(file));
}
diff --git a/security/ipe/eval.h b/security/ipe/eval.h
index 25d2d8d55702..d51280f0519f 100644
--- a/security/ipe/eval.h
+++ b/security/ipe/eval.h
@@ -21,6 +21,14 @@ struct ipe_bdev {
size_t hashlen;
};

+struct ipe_inode {
+ const u8 *sigdata;
+ size_t siglen;
+
+ const u8 *hash;
+ size_t hashlen;
+};
+
struct ipe_eval_ctx {
enum ipe_hook hook;
enum ipe_operation op;
@@ -29,6 +37,7 @@ struct ipe_eval_ctx {
struct ipe_context *ci_ctx;

const struct ipe_bdev *ipe_bdev;
+ const struct ipe_inode *ipe_inode;

bool from_init_sb;
};
diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index d76e60a3f511..78bb3451220a 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -268,3 +268,61 @@ int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,

return -ENOSYS;
}
+
+/**
+ * ipe_inode_setsecurity: Sets the a certain field of a inode security
+ * blob, based on @key.
+ * @inode: The inode to source the security blob from.
+ * @name: The name representing the information to be stored.
+ * @value: The value to be stored.
+ * @size: The size of @value.
+ * @flags: unused
+ *
+ * Saves fsverity signature & digest into inode security blob
+ *
+ * Return:
+ * 0 - OK
+ * !0 - Error
+ */
+int ipe_inode_setsecurity(struct inode *inode, const char *name,
+ const void *value, size_t size,
+ int flags)
+{
+ struct ipe_inode *inode_sec = ipe_inode(inode);
+
+ if (!strcmp(name, FS_VERITY_SIGNATURE_SEC_NAME)) {
+ inode_sec->siglen = size;
+ inode_sec->sigdata = kmemdup(value, size, GFP_KERNEL);
+ if (!inode_sec->sigdata)
+ return -ENOMEM;
+
+ return 0;
+ }
+
+ if (!strcmp(name, FS_VERITY_DIGEST_SEC_NAME)) {
+ inode_sec->hashlen = size;
+ inode_sec->hash = kmemdup(value, size, GFP_KERNEL);
+ if (!inode_sec->hash)
+ return -ENOMEM;
+
+ return 0;
+ }
+
+ return -EOPNOTSUPP;
+}
+
+/**
+ * ipe_node_free_security: Frees all fields of IPE's inode security blob.
+ * @inode: The inode structure to source the security blob from.
+ *
+ * The deallocation of the blob itself is performed later by the LSM
+ * infrastructure, (on behalf of all LSMs) in lsm_free_file.
+ *
+ */
+void ipe_inode_free_security(struct inode *inode)
+{
+ struct ipe_inode *inode_sec = ipe_inode(inode);
+
+ kfree(inode_sec->sigdata);
+ kfree(inode_sec->hash);
+}
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index 285f35187188..d6f8c05a8011 100644
--- a/security/ipe/hooks.h
+++ b/security/ipe/hooks.h
@@ -10,6 +10,7 @@
#include <linux/sched.h>
#include <linux/binfmts.h>
#include <linux/security.h>
+#include <linux/fsverity.h>
#include <linux/device-mapper.h>

enum ipe_hook {
@@ -46,4 +47,10 @@ void ipe_bdev_free_security(struct block_device *bdev);
int ipe_bdev_setsecurity(struct block_device *bdev, const char *key,
const void *value, size_t len);

+void ipe_inode_free_security(struct inode *inode);
+
+int ipe_inode_setsecurity(struct inode *inode, const char *name,
+ const void *value, size_t size,
+ int flags);
+
#endif /* IPE_HOOKS_H */
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 215936cb4574..c7ecd542c317 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -22,6 +22,7 @@
struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = {
.lbs_task = sizeof(struct ipe_context __rcu *),
.lbs_bdev = sizeof(struct ipe_bdev),
+ .lbs_inode = sizeof(struct ipe_inode),
};

struct ipe_bdev *ipe_bdev(struct block_device *b)
@@ -29,6 +30,11 @@ struct ipe_bdev *ipe_bdev(struct block_device *b)
return b->security + ipe_blobs.lbs_bdev;
}

+struct ipe_inode *ipe_inode(const struct inode *inode)
+{
+ return inode->i_security + ipe_blobs.lbs_inode;
+}
+
static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(task_alloc, ipe_task_alloc),
LSM_HOOK_INIT(task_free, ipe_task_free),
@@ -40,6 +46,8 @@ static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security),
LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security),
LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity),
+ LSM_HOOK_INIT(inode_setsecurity, ipe_inode_setsecurity),
+ LSM_HOOK_INIT(inode_free_security, ipe_inode_free_security),
};

/**
diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
index 6b4c7e07f204..16d843614fac 100644
--- a/security/ipe/ipe.h
+++ b/security/ipe/ipe.h
@@ -22,5 +22,6 @@ extern struct ipe_parser __start_ipe_parsers[], __end_ipe_parsers[];
extern struct ipe_module __start_ipe_modules[], __end_ipe_modules[];

struct ipe_bdev *ipe_bdev(struct block_device *b);
+struct ipe_inode *ipe_inode(const struct inode *inode);

#endif /* IPE_H */
diff --git a/security/ipe/modules/Kconfig b/security/ipe/modules/Kconfig
index a6ea06cf0737..8f823a1edf96 100644
--- a/security/ipe/modules/Kconfig
+++ b/security/ipe/modules/Kconfig
@@ -40,4 +40,27 @@ config IPE_PROP_DM_VERITY_ROOTHASH

If unsure, answer Y.

+config IPE_PROP_FS_VERITY_SIGNATURE
+ bool "Enable property for signed fs-verity files"
+ depends on FS_VERITY_BUILTIN_SIGNATURES
+ help
+ This option enables IPE's integration with FSVerity's
+ signed hashes. This enables the usage of the property,
+ "fsverity_signature" in IPE's policy.
+
+ if unsure, answer Y.
+
+config IPE_PROP_FS_VERITY_DIGEST
+ bool "Enable property for authorizing fs-verity files via digest"
+ depends on FS_VERITY
+ help
+ This option enables IPE's integration with FSVerity.
+ This enables the usage of the property "fsverity_digest" in IPE's
+ policy. This property allows authorization or revocation via a
+ a hex-string representing the digest of a fsverity file.
+
+ if unsure, answer Y.
+
+
+
endmenu
diff --git a/security/ipe/modules/Makefile b/security/ipe/modules/Makefile
index 84fadce85193..890440b9050f 100644
--- a/security/ipe/modules/Makefile
+++ b/security/ipe/modules/Makefile
@@ -8,3 +8,5 @@
obj-$(CONFIG_IPE_PROP_BOOT_VERIFIED) += boot_verified.o
obj-$(CONFIG_IPE_PROP_DM_VERITY_SIGNATURE) += dmverity_signature.o
obj-$(CONFIG_IPE_PROP_DM_VERITY_ROOTHASH) += dmverity_roothash.o
+obj-$(CONFIG_IPE_PROP_FS_VERITY_SIGNATURE) += fsverity_signature.o
+obj-$(CONFIG_IPE_PROP_FS_VERITY_DIGEST) += fsverity_digest.o
diff --git a/security/ipe/modules/fsverity_digest.c b/security/ipe/modules/fsverity_digest.c
new file mode 100644
index 000000000000..67944ebbb8d5
--- /dev/null
+++ b/security/ipe/modules/fsverity_digest.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include "ipe_module.h"
+
+#include <linux/fs.h>
+#include <linux/types.h>
+
+struct counted_array {
+ size_t len;
+ u8 *data;
+};
+
+static int parse(const char *valstr, void **value)
+{
+ int rv = 0;
+ struct counted_array *arr;
+
+ arr = kzalloc(sizeof(*arr), GFP_KERNEL);
+ if (!arr) {
+ rv = -ENOMEM;
+ goto err;
+ }
+
+ arr->len = (strlen(valstr) / 2);
+
+ arr->data = kzalloc(arr->len, GFP_KERNEL);
+ if (!arr->data) {
+ rv = -ENOMEM;
+ goto err;
+ }
+
+ rv = hex2bin(arr->data, valstr, arr->len);
+ if (rv != 0)
+ goto err2;
+
+ *value = arr;
+ return rv;
+err2:
+ kfree(arr->data);
+err:
+ kfree(arr);
+ return rv;
+}
+
+static bool evaluate(const struct ipe_eval_ctx *ctx, const void *val)
+{
+ const u8 *src;
+ struct counted_array *expect = (struct counted_array *)val;
+
+ if (!ctx->ipe_inode)
+ return false;
+
+ if (ctx->ipe_inode->hashlen != expect->len)
+ return false;
+
+ src = ctx->ipe_inode->hash;
+
+ return !memcmp(expect->data, src, expect->len);
+}
+
+static int free_value(void **val)
+{
+ struct counted_array *expect = (struct counted_array *)val;
+
+ kfree(expect->data);
+ kfree(expect);
+
+ return 0;
+}
+
+IPE_MODULE(fsv_digest) = {
+ .name = "fsverity_digest",
+ .version = 1,
+ .parse = parse,
+ .free = free_value,
+ .eval = evaluate,
+};
diff --git a/security/ipe/modules/fsverity_signature.c b/security/ipe/modules/fsverity_signature.c
new file mode 100644
index 000000000000..8930a8961f61
--- /dev/null
+++ b/security/ipe/modules/fsverity_signature.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include "ipe_module.h"
+
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/audit.h>
+#include <linux/mount.h>
+
+static bool evaluate(const struct ipe_eval_ctx *ctx, const void *value)
+{
+ bool expect = (bool)value;
+
+ if (!ctx->file)
+ return false;
+
+ if (!IS_VERITY(ctx->file->f_inode) || !ctx->ipe_inode)
+ return false;
+
+ return (!!ctx->ipe_inode->sigdata) == expect;
+}
+
+IPE_MODULE(fsvs) = {
+ .name = "fsverity_signature",
+ .version = 1,
+ .parse = ipe_bool_parse,
+ .free = NULL,
+ .eval = evaluate,
+};
--
2.33.0