[PATCH v4 06/14] digest_cache: Parse tlv digest lists

Roberto Sassu
2024-04-15T14:26:47Z

From: Roberto Sassu <roberto.sassu@huawei.com>

Add digest_list_parse_tlv(), to parse TLV-formatted (Type Length Value)
digest lists. Their structure is:

[header: DIGEST_LIST_FILE, num fields, total len]
[field: DIGEST_LIST_ALGO, length, value]
[field: DIGEST_LIST_ENTRY#1, length, value (below)]
|- [header: DIGEST_LIST_ENTRY_DATA, num fields, total len]
|- [DIGEST_LIST_ENTRY_DIGEST#1, length, file digest]
|- [DIGEST_LIST_ENTRY_PATH#1, length, file path]
[field: DIGEST_LIST_ENTRY#N, length, value (below)]
|- [header: DIGEST_LIST_ENTRY_DATA, num fields, total len]
|- [DIGEST_LIST_ENTRY_DIGEST#N, length, file digest]
|- [DIGEST_LIST_ENTRY_PATH#N, length, file path]

DIGEST_LIST_ALGO must have a fixed length of sizeof(u64).

The data of the DIGEST_LIST_ENTRY field are itself in TLV format.

Currently defined fields are sufficient for measurement/appraisal of file
data. More fields will be introduced later for file metadata.

Introduce digest_list_file_callback() to handle the DIGEST_LIST_FILE
fields, DIGEST_LIST_ALGO and DIGEST_LIST_ENTRY, and the respective field
parsers parse_digest_list_algo() and parse_digest_list_entry().

Also introduce digest_list_entry_data_callback(), to handle the
DIGEST_LIST_ENTRY_DATA (nested) fields, DIGEST_LIST_ENTRY_DIGEST and
DIGEST_LIST_ENTRY_PATH, and the respective field parsers
parse_digest_list_entry_digest() and parse_digest_list_entry_path().

The TLV parser itself is defined in lib/tlv_parser.c.

Both the TLV parser and the tlv digest list parser have been formally
verified with Frama-C (https://frama-c.com/).

The analysis has been done on this file:

https://github.com/robertosassu/rpm-formal/blob/main/validate_tlv.c

Here is the result of the analysis:

[eva:summary] ====== ANALYSIS SUMMARY ======
---------------------------------------------------------------------------
13 functions analyzed (out of 13): 100% coverage.
In these functions, 240 statements reached (out of 254): 94% coverage.
---------------------------------------------------------------------------
Some errors and warnings have been raised during the analysis:
by the Eva analyzer: 0 errors 4 warnings
by the Frama-C kernel: 0 errors 0 warnings
---------------------------------------------------------------------------
0 alarms generated by the analysis.
---------------------------------------------------------------------------
Evaluation of the logical properties reached by the analysis:
Assertions 5 valid 0 unknown 0 invalid 5 total
Preconditions 24 valid 0 unknown 0 invalid 24 total
100% of the logical properties reached have been proven.
---------------------------------------------------------------------------

The warnings are:

[eva] validate_tlv.c:437: Warning:
this partitioning parameter cannot be evaluated safely on all states
[eva] validate_tlv.c:445: Warning:
this partitioning parameter cannot be evaluated safely on all states
[eva] validate_tlv.c:354: Warning:
this partitioning parameter cannot be evaluated safely on all states
[eva] validate_tlv.c:382: Warning:
this partitioning parameter cannot be evaluated safely on all states

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
include/uapi/linux/tlv_digest_list.h | 72 ++++++
security/digest_cache/Kconfig | 1 +
security/digest_cache/Makefile | 2 +
security/digest_cache/parsers/parsers.h | 13 ++
security/digest_cache/parsers/tlv.c | 299 ++++++++++++++++++++++++
security/digest_cache/populate.c | 4 +
6 files changed, 391 insertions(+)
create mode 100644 include/uapi/linux/tlv_digest_list.h
create mode 100644 security/digest_cache/parsers/parsers.h
create mode 100644 security/digest_cache/parsers/tlv.c

diff --git a/include/uapi/linux/tlv_digest_list.h b/include/uapi/linux/tlv_digest_list.h
new file mode 100644
index 000000000000..8c97a46901c1
--- /dev/null
+++ b/include/uapi/linux/tlv_digest_list.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (C) 2017-2024 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@huawei.com>
+ *
+ * Export definitions of the tlv digest list.
+ */
+
+#ifndef _UAPI_LINUX_TLV_DIGEST_LIST_H
+#define _UAPI_LINUX_TLV_DIGEST_LIST_H
+
+#include <linux/types.h>
+
+#define FOR_EACH_DIGEST_LIST_TYPE(DIGEST_LIST_TYPE) \
+ DIGEST_LIST_TYPE(DIGEST_LIST_FILE) \
+ DIGEST_LIST_TYPE(DIGEST_LIST__LAST)
+
+#define FOR_EACH_DIGEST_LIST_FIELD(DIGEST_LIST_FIELD) \
+ DIGEST_LIST_FIELD(DIGEST_LIST_ALGO) \
+ DIGEST_LIST_FIELD(DIGEST_LIST_ENTRY) \
+ DIGEST_LIST_FIELD(DIGEST_LIST_FIELD__LAST)
+
+#define FOR_EACH_DIGEST_LIST_ENTRY_TYPE(DIGEST_LIST_ENTRY_TYPE) \
+ DIGEST_LIST_ENTRY_TYPE(DIGEST_LIST_ENTRY_DATA) \
+ DIGEST_LIST_ENTRY_TYPE(DIGEST_LIST_ENTRY__LAST)
+
+#define FOR_EACH_DIGEST_LIST_ENTRY_FIELD(DIGEST_LIST_ENTRY_FIELD) \
+ DIGEST_LIST_ENTRY_FIELD(DIGEST_LIST_ENTRY_DIGEST) \
+ DIGEST_LIST_ENTRY_FIELD(DIGEST_LIST_ENTRY_PATH) \
+ DIGEST_LIST_ENTRY_FIELD(DIGEST_LIST_ENTRY_FIELD__LAST)
+
+#define GENERATE_ENUM(ENUM) ENUM,
+#define GENERATE_STRING(STRING) #STRING,
+
+/**
+ * enum digest_list_types - Types of digest list
+ *
+ * Enumerates the types of digest list to parse.
+ */
+enum digest_list_types {
+ FOR_EACH_DIGEST_LIST_TYPE(GENERATE_ENUM)
+};
+
+/**
+ * enum digest_list_fields - Digest list fields
+ *
+ * Enumerates the digest list fields.
+ */
+enum digest_list_fields {
+ FOR_EACH_DIGEST_LIST_FIELD(GENERATE_ENUM)
+};
+
+/**
+ * enum digest_list_entry_types - Types of data stored in DIGEST_LIST_ENTRY
+ *
+ * Enumerates the types of data stored in DIGEST_LIST_ENTRY (nested TLV data).
+ */
+enum digest_list_entry_types {
+ FOR_EACH_DIGEST_LIST_ENTRY_TYPE(GENERATE_ENUM)
+};
+
+/**
+ * enum digest_list_entry_fields - DIGEST_LIST_ENTRY fields
+ *
+ * Enumerates the DIGEST_LIST_ENTRY fields.
+ */
+enum digest_list_entry_fields {
+ FOR_EACH_DIGEST_LIST_ENTRY_FIELD(GENERATE_ENUM)
+};
+
+#endif /* _UAPI_LINUX_TLV_DIGEST_LIST_H */
diff --git a/security/digest_cache/Kconfig b/security/digest_cache/Kconfig
index 71017954e5c5..cb4fa44e8f2a 100644
--- a/security/digest_cache/Kconfig
+++ b/security/digest_cache/Kconfig
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
config SECURITY_DIGEST_CACHE
bool "Digest_cache LSM"
+ select TLV_PARSER
default n
help
This option enables an LSM maintaining a cache of digests
diff --git a/security/digest_cache/Makefile b/security/digest_cache/Makefile
index c1452437d02f..a383b6ef2550 100644
--- a/security/digest_cache/Makefile
+++ b/security/digest_cache/Makefile
@@ -5,3 +5,5 @@
obj-$(CONFIG_SECURITY_DIGEST_CACHE) += digest_cache.o

digest_cache-y := main.o secfs.o htable.o populate.o modsig.o
+
+digest_cache-y += parsers/tlv.o
diff --git a/security/digest_cache/parsers/parsers.h b/security/digest_cache/parsers/parsers.h
new file mode 100644
index 000000000000..1bbae426ab9f
--- /dev/null
+++ b/security/digest_cache/parsers/parsers.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023-2024 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@huawei.com>
+ *
+ * Digest list parsers.
+ */
+
+#include "../internal.h"
+
+int digest_list_parse_tlv(struct digest_cache *digest_cache, const u8 *data,
+ size_t data_len);
diff --git a/security/digest_cache/parsers/tlv.c b/security/digest_cache/parsers/tlv.c
new file mode 100644
index 000000000000..97e2c36b93a8
--- /dev/null
+++ b/security/digest_cache/parsers/tlv.c
@@ -0,0 +1,299 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017-2024 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@huawei.com>
+ *
+ * Parse a tlv digest list.
+ */
+
+#define pr_fmt(fmt) "TLV DIGEST LIST: "fmt
+#include <linux/tlv_parser.h>
+#include <uapi/linux/tlv_digest_list.h>
+
+#include "parsers.h"
+
+#define kenter(FMT, ...) \
+ pr_debug("==> %s(" FMT ")\n", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+ pr_debug("<== %s()" FMT "\n", __func__, ##__VA_ARGS__)
+
+const char *digest_list_types_str[] = {
+ FOR_EACH_DIGEST_LIST_TYPE(GENERATE_STRING)
+};
+
+const char *digest_list_fields_str[] = {
+ FOR_EACH_DIGEST_LIST_FIELD(GENERATE_STRING)
+};
+
+const char *digest_list_entry_types_str[] = {
+ FOR_EACH_DIGEST_LIST_ENTRY_TYPE(GENERATE_STRING)
+};
+
+const char *digest_list_entry_fields_str[] = {
+ FOR_EACH_DIGEST_LIST_ENTRY_FIELD(GENERATE_STRING)
+};
+
+struct tlv_callback_data {
+ struct digest_cache *digest_cache;
+ u64 parsed_data_type;
+ u64 parsed_num_entries;
+ u64 parsed_total_len;
+ enum hash_algo algo;
+};
+
+/**
+ * parse_digest_list_entry_digest - Parse DIGEST_LIST_ENTRY_DIGEST field
+ * @tlv_data: Parser callback data
+ * @field: Field identifier
+ * @field_data: Field data
+ * @field_data_len: Length of @field_data
+ *
+ * This function parses the DIGEST_LIST_ENTRY_DIGEST field (file digest).
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+static int parse_digest_list_entry_digest(struct tlv_callback_data *tlv_data,
+ enum digest_list_entry_fields field,
+ const u8 *field_data,
+ u64 field_data_len)
+{
+ int ret;
+
+ kenter(",%u,%llu", field, field_data_len);
+
+ if (tlv_data->algo == HASH_ALGO__LAST) {
+ pr_debug("Digest algo not set\n");
+ ret = -EBADMSG;
+ goto out;
+ }
+
+ if (field_data_len != hash_digest_size[tlv_data->algo]) {
+ pr_debug("Unexpected data length %llu, expected %d\n",
+ field_data_len, hash_digest_size[tlv_data->algo]);
+ ret = -EBADMSG;
+ goto out;
+ }
+
+ ret = digest_cache_htable_add(tlv_data->digest_cache, (u8 *)field_data,
+ tlv_data->algo);
+out:
+ kleave(" = %d", ret);
+ return ret;
+}
+
+/**
+ * parse_digest_list_entry_path - Parse DIGEST_LIST_ENTRY_PATH field
+ * @tlv_data: Parser callback data
+ * @field: Field identifier
+ * @field_data: Field data
+ * @field_data_len: Length of @field_data
+ *
+ * This function handles the DIGEST_LIST_ENTRY_PATH field (file path). It
+ * currently does not parse the data.
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+static int parse_digest_list_entry_path(struct tlv_callback_data *tlv_data,
+ enum digest_list_entry_fields field,
+ const u8 *field_data,
+ u64 field_data_len)
+{
+ kenter(",%u,%llu", field, field_data_len);
+
+ kleave(" = 0");
+ return 0;
+}
+
+/**
+ * digest_list_entry_data_callback - DIGEST_LIST_ENTRY_DATA callback
+ * @callback_data: Callback data
+ * @field: Field identifier
+ * @field_data: Field data
+ * @field_data_len: Length of @field_data
+ *
+ * This callback handles the fields of DIGEST_LIST_ENTRY_DATA (nested) data,
+ * and calls the appropriate parser.
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+static int digest_list_entry_data_callback(void *callback_data, u64 field,
+ const u8 *field_data,
+ u64 field_data_len)
+{
+ struct tlv_callback_data *tlv_data;
+ int ret;
+
+ tlv_data = (struct tlv_callback_data *)callback_data;
+
+ switch (field) {
+ case DIGEST_LIST_ENTRY_DIGEST:
+ ret = parse_digest_list_entry_digest(tlv_data, field,
+ field_data,
+ field_data_len);
+ break;
+ case DIGEST_LIST_ENTRY_PATH:
+ ret = parse_digest_list_entry_path(tlv_data, field, field_data,
+ field_data_len);
+ break;
+ default:
+ pr_debug("Unhandled field %s\n",
+ digest_list_entry_fields_str[field]);
+ /* Just ignore non-relevant fields. */
+ ret = 0;
+ break;
+ }
+
+ return ret;
+}
+
+/**
+ * parse_digest_list_algo - Parse DIGEST_LIST_ALGO field
+ * @tlv_data: Parser callback data
+ * @field: Field identifier
+ * @field_data: Field data
+ * @field_data_len: Length of @field_data
+ *
+ * This function parses the DIGEST_LIST_ALGO field (digest algorithm).
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+static int parse_digest_list_algo(struct tlv_callback_data *tlv_data,
+ enum digest_list_fields field,
+ const u8 *field_data, u64 field_data_len)
+{
+ u64 algo;
+ int ret;
+
+ kenter(",%u,%llu", field, field_data_len);
+
+ if (field_data_len != sizeof(u64)) {
+ pr_debug("Unexpected data length %llu, expected %lu\n",
+ field_data_len, sizeof(u64));
+ ret = -EBADMSG;
+ goto out;
+ }
+
+ algo = __be64_to_cpu(*(u64 *)field_data);
+
+ if (algo >= HASH_ALGO__LAST) {
+ pr_debug("Unexpected digest algo %llu\n", algo);
+ ret = -EBADMSG;
+ goto out;
+ }
+
+ ret = digest_cache_htable_init(tlv_data->digest_cache,
+ tlv_data->parsed_num_entries, algo);
+ if (ret < 0)
+ goto out;
+
+ tlv_data->algo = algo;
+
+ pr_debug("Digest algo: %s\n", hash_algo_name[algo]);
+out:
+ kleave(" = %d", ret);
+ return ret;
+}
+
+/**
+ * parse_digest_list_entry - Parse DIGEST_LIST_ENTRY field
+ * @tlv_data: Parser callback data
+ * @field: Field identifier
+ * @field_data: Field data
+ * @field_data_len: Length of @field_data
+ *
+ * This function parses the DIGEST_LIST_ENTRY field.
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+static int parse_digest_list_entry(struct tlv_callback_data *tlv_data,
+ enum digest_list_fields field,
+ const u8 *field_data, u64 field_data_len)
+{
+ int ret;
+
+ kenter(",%u,%llu", field, field_data_len);
+
+ ret = tlv_parse(DIGEST_LIST_ENTRY_DATA, digest_list_entry_data_callback,
+ tlv_data, field_data, field_data_len,
+ digest_list_entry_types_str, DIGEST_LIST_ENTRY__LAST,
+ digest_list_entry_fields_str,
+ DIGEST_LIST_ENTRY_FIELD__LAST);
+
+ kleave(" = %d", ret);
+ return ret;
+}
+
+/**
+ * digest_list_file_callback - DIGEST_LIST_FILE callback
+ * @callback_data: Callback data
+ * @field: Field identifier
+ * @field_data: Field data
+ * @field_data_len: Length of @field_data
+ *
+ * This callback handles the fields of DIGEST_LIST_FILE data, and calls the
+ * appropriate parser.
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+static int digest_list_file_callback(void *callback_data, u64 field,
+ const u8 *field_data, u64 field_data_len)
+{
+ struct tlv_callback_data *tlv_data;
+ int ret;
+
+ tlv_data = (struct tlv_callback_data *)callback_data;
+
+ switch (field) {
+ case DIGEST_LIST_ALGO:
+ ret = parse_digest_list_algo(tlv_data, field, field_data,
+ field_data_len);
+ break;
+ case DIGEST_LIST_ENTRY:
+ ret = parse_digest_list_entry(tlv_data, field, field_data,
+ field_data_len);
+ break;
+ default:
+ pr_debug("Unhandled field %s\n",
+ digest_list_fields_str[field]);
+ /* Just ignore non-relevant fields. */
+ ret = 0;
+ break;
+ }
+
+ return ret;
+}
+
+/**
+ * digest_list_parse_tlv - Parse a tlv digest list
+ * @digest_cache: Digest cache
+ * @data: Data to parse
+ * @data_len: Length of @data
+ *
+ * This function parses a tlv digest list.
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+int digest_list_parse_tlv(struct digest_cache *digest_cache, const u8 *data,
+ size_t data_len)
+{
+ struct tlv_callback_data tlv_data = {
+ .digest_cache = digest_cache,
+ .algo = HASH_ALGO__LAST
+ };
+ int ret;
+
+ ret = tlv_parse_hdr(&data, &data_len, &tlv_data.parsed_data_type,
+ &tlv_data.parsed_num_entries,
+ &tlv_data.parsed_total_len,
+ digest_list_types_str, DIGEST_LIST__LAST);
+ if (ret < 0)
+ return ret;
+
+ if (tlv_data.parsed_data_type != DIGEST_LIST_FILE)
+ return 0;
+
+ return tlv_parse_data(digest_list_file_callback, &tlv_data,
+ tlv_data.parsed_num_entries, data, data_len,
+ digest_list_fields_str, DIGEST_LIST_FIELD__LAST);
+}
diff --git a/security/digest_cache/populate.c b/security/digest_cache/populate.c
index 415e638f587b..13645ec4bb2b 100644
--- a/security/digest_cache/populate.c
+++ b/security/digest_cache/populate.c
@@ -12,6 +12,7 @@
#include <linux/kernel_read_file.h>

#include "internal.h"
+#include "parsers/parsers.h"

/**
* digest_cache_parse_digest_list - Parse a digest list
@@ -65,6 +66,9 @@ static int digest_cache_parse_digest_list(struct digest_cache *digest_cache,
filename[0] ? "/" : "", filename, (int)(next_sep - format),
format, data_len);

+ if (!strncmp(format, "tlv-", 4))
+ ret = digest_list_parse_tlv(digest_cache, data, data_len);
+
return ret;
}

--
2.34.1