[PATCH v4 07/14] digest_cache: Parse rpm digest lists

Roberto Sassu
2024-04-15T14:27:01Z

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

Implement a simple parser of RPM headers, that extracts the digest and the
algorithm of the packaged files from the RPMTAG_FILEDIGESTS and
RPMTAG_FILEDIGESTALGO section, and add them to the digest cache.

The rpm digest list parser has been 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_rpm.c

Here is the result of the analysis:

[eva:summary] ====== ANALYSIS SUMMARY ======
---------------------------------------------------------------------------
7 functions analyzed (out of 7): 100% coverage.
In these functions, 228 statements reached (out of 246): 92% coverage.
---------------------------------------------------------------------------
No errors or warnings raised during the analysis.
---------------------------------------------------------------------------
0 alarms generated by the analysis.
---------------------------------------------------------------------------
Evaluation of the logical properties reached by the analysis:
Assertions 6 valid 0 unknown 0 invalid 6 total
Preconditions 29 valid 0 unknown 0 invalid 29 total
100% of the logical properties reached have been proven.
---------------------------------------------------------------------------

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/digest_cache/Makefile | 1 +
security/digest_cache/parsers/parsers.h | 2 +
security/digest_cache/parsers/rpm.c | 223 ++++++++++++++++++++++++
security/digest_cache/populate.c | 2 +
4 files changed, 228 insertions(+)
create mode 100644 security/digest_cache/parsers/rpm.c

diff --git a/security/digest_cache/Makefile b/security/digest_cache/Makefile
index a383b6ef2550..eca4076497e6 100644
--- a/security/digest_cache/Makefile
+++ b/security/digest_cache/Makefile
@@ -7,3 +7,4 @@ 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
+digest_cache-y += parsers/rpm.o
diff --git a/security/digest_cache/parsers/parsers.h b/security/digest_cache/parsers/parsers.h
index 1bbae426ab9f..3f00d29ed92a 100644
--- a/security/digest_cache/parsers/parsers.h
+++ b/security/digest_cache/parsers/parsers.h
@@ -11,3 +11,5 @@

int digest_list_parse_tlv(struct digest_cache *digest_cache, const u8 *data,
size_t data_len);
+int digest_list_parse_rpm(struct digest_cache *digest_cache, const u8 *data,
+ size_t data_len);
diff --git a/security/digest_cache/parsers/rpm.c b/security/digest_cache/parsers/rpm.c
new file mode 100644
index 000000000000..6c7fe9c9121c
--- /dev/null
+++ b/security/digest_cache/parsers/rpm.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017-2024 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@huawei.com>
+ *
+ * Parse an rpm digest list (RPM package header).
+ */
+
+#define pr_fmt(fmt) "RPM DIGEST LIST: "fmt
+#include <linux/module.h>
+
+#include "parsers.h"
+
+#define RPMTAG_FILEDIGESTS 1035
+#define RPMTAG_FILEDIGESTALGO 5011
+
+#define RPM_INT32_TYPE 4
+#define RPM_STRING_ARRAY_TYPE 8
+
+struct rpm_hdr {
+ u32 magic;
+ u32 reserved;
+ u32 tags;
+ u32 datasize;
+} __packed;
+
+struct rpm_entryinfo {
+ s32 tag;
+ u32 type;
+ s32 offset;
+ u32 count;
+} __packed;
+
+enum pgp_algos {
+ DIGEST_ALGO_MD5 = 1,
+ DIGEST_ALGO_SHA1 = 2,
+ DIGEST_ALGO_RMD160 = 3,
+ /* 4, 5, 6, and 7 are reserved. */
+ DIGEST_ALGO_SHA256 = 8,
+ DIGEST_ALGO_SHA384 = 9,
+ DIGEST_ALGO_SHA512 = 10,
+ DIGEST_ALGO_SHA224 = 11,
+};
+
+static const enum hash_algo pgp_algo_mapping[DIGEST_ALGO_SHA224 + 1] = {
+ [DIGEST_ALGO_MD5] = HASH_ALGO_MD5,
+ [DIGEST_ALGO_SHA1] = HASH_ALGO_SHA1,
+ [DIGEST_ALGO_RMD160] = HASH_ALGO_RIPE_MD_160,
+ [4] = HASH_ALGO__LAST,
+ [5] = HASH_ALGO__LAST,
+ [6] = HASH_ALGO__LAST,
+ [7] = HASH_ALGO__LAST,
+ [DIGEST_ALGO_SHA256] = HASH_ALGO_SHA256,
+ [DIGEST_ALGO_SHA384] = HASH_ALGO_SHA384,
+ [DIGEST_ALGO_SHA512] = HASH_ALGO_SHA512,
+ [DIGEST_ALGO_SHA224] = HASH_ALGO_SHA224,
+};
+
+/**
+ * digest_list_parse_rpm - Parse an rpm digest list
+ * @digest_cache: Digest cache
+ * @data: Data to parse
+ * @data_len: Length of @data
+ *
+ * This function parses an rpm digest list.
+ *
+ * Return: Zero on success, a POSIX error code otherwise.
+ */
+int digest_list_parse_rpm(struct digest_cache *digest_cache, const u8 *data,
+ size_t data_len)
+{
+ const unsigned char rpm_header_magic[8] = {
+ 0x8e, 0xad, 0xe8, 0x01, 0x00, 0x00, 0x00, 0x00
+ };
+ const struct rpm_hdr *hdr;
+ const struct rpm_entryinfo *entry;
+ u32 tags, max_tags, datasize;
+ u32 digests_count, max_digests_count;
+ u32 digests_offset, algo_offset;
+ u32 digest_len, pkg_pgp_algo, i;
+ bool algo_offset_set = false, digests_offset_set = false;
+ enum hash_algo pkg_kernel_algo = HASH_ALGO_MD5;
+ u8 rpm_digest[SHA512_DIGEST_SIZE];
+ int ret;
+
+ if (data_len < sizeof(*hdr)) {
+ pr_debug("Not enough data for RPM header, current %ld, expected: %ld\n",
+ data_len, sizeof(*hdr));
+ return -EINVAL;
+ }
+
+ if (memcmp(data, rpm_header_magic, sizeof(rpm_header_magic))) {
+ pr_debug("RPM header magic mismatch\n");
+ return -EINVAL;
+ }
+
+ hdr = (const struct rpm_hdr *)data;
+ data += sizeof(*hdr);
+ data_len -= sizeof(*hdr);
+
+ tags = __be32_to_cpu(hdr->tags);
+ max_tags = data_len / sizeof(*entry);
+
+ /* Finite termination on tags loop. */
+ if (tags > max_tags)
+ return -EINVAL;
+
+ datasize = __be32_to_cpu(hdr->datasize);
+ if (datasize != data_len - tags * sizeof(*entry))
+ return -EINVAL;
+
+ pr_debug("Scanning %d RPM header sections\n", tags);
+ for (i = 0; i < tags; i++) {
+ if (data_len < sizeof(*entry))
+ return -EINVAL;
+
+ entry = (const struct rpm_entryinfo *)data;
+ data += sizeof(*entry);
+ data_len -= sizeof(*entry);
+
+ switch (__be32_to_cpu(entry->tag)) {
+ case RPMTAG_FILEDIGESTS:
+ if (__be32_to_cpu(entry->type) != RPM_STRING_ARRAY_TYPE)
+ return -EINVAL;
+
+ digests_offset = __be32_to_cpu(entry->offset);
+ digests_count = __be32_to_cpu(entry->count);
+ digests_offset_set = true;
+
+ pr_debug("Found RPMTAG_FILEDIGESTS at offset %u, count: %u\n",
+ digests_offset, digests_count);
+ break;
+ case RPMTAG_FILEDIGESTALGO:
+ if (__be32_to_cpu(entry->type) != RPM_INT32_TYPE)
+ return -EINVAL;
+
+ algo_offset = __be32_to_cpu(entry->offset);
+ algo_offset_set = true;
+
+ pr_debug("Found RPMTAG_FILEDIGESTALGO at offset %u\n",
+ algo_offset);
+ break;
+ default:
+ break;
+ }
+ }
+
+ if (!digests_offset_set)
+ return 0;
+
+ if (algo_offset_set) {
+ if (algo_offset >= data_len)
+ return -EINVAL;
+
+ if (data_len - algo_offset < sizeof(u32))
+ return -EINVAL;
+
+ pkg_pgp_algo = *(u32 *)&data[algo_offset];
+ pkg_pgp_algo = __be32_to_cpu(pkg_pgp_algo);
+ if (pkg_pgp_algo > DIGEST_ALGO_SHA224) {
+ pr_debug("Unknown PGP algo %d\n", pkg_pgp_algo);
+ return -EINVAL;
+ }
+
+ pkg_kernel_algo = pgp_algo_mapping[pkg_pgp_algo];
+ if (pkg_kernel_algo >= HASH_ALGO__LAST) {
+ pr_debug("Unknown mapping for PGP algo %d\n",
+ pkg_pgp_algo);
+ return -EINVAL;
+ }
+
+ pr_debug("Found mapping for PGP algo %d: %s\n", pkg_pgp_algo,
+ hash_algo_name[pkg_kernel_algo]);
+ }
+
+ digest_len = hash_digest_size[pkg_kernel_algo];
+
+ if (digests_offset > data_len)
+ return -EINVAL;
+
+ /* Worst case, every digest is a \0. */
+ max_digests_count = data_len - digests_offset;
+
+ /* Finite termination on digests_count loop. */
+ if (digests_count > max_digests_count)
+ return -EINVAL;
+
+ ret = digest_cache_htable_init(digest_cache, digests_count,
+ pkg_kernel_algo);
+ if (ret < 0)
+ return ret;
+
+ for (i = 0; i < digests_count; i++) {
+ if (digests_offset == data_len)
+ return -EINVAL;
+
+ if (!data[digests_offset]) {
+ digests_offset++;
+ continue;
+ }
+
+ if (data_len - digests_offset < digest_len * 2 + 1)
+ return -EINVAL;
+
+ ret = hex2bin(rpm_digest, (const char *)&data[digests_offset],
+ digest_len);
+ if (ret < 0) {
+ pr_debug("Invalid hex format for digest %s\n",
+ &data[digests_offset]);
+ return -EINVAL;
+ }
+
+ ret = digest_cache_htable_add(digest_cache, rpm_digest,
+ pkg_kernel_algo);
+ if (ret < 0)
+ return ret;
+
+ digests_offset += digest_len * 2 + 1;
+ }
+
+ return ret;
+}
diff --git a/security/digest_cache/populate.c b/security/digest_cache/populate.c
index 13645ec4bb2b..1770c8385017 100644
--- a/security/digest_cache/populate.c
+++ b/security/digest_cache/populate.c
@@ -68,6 +68,8 @@ static int digest_cache_parse_digest_list(struct digest_cache *digest_cache,

if (!strncmp(format, "tlv-", 4))
ret = digest_list_parse_tlv(digest_cache, data, data_len);
+ else if (!strncmp(format, "rpm-", 4))
+ ret = digest_list_parse_rpm(digest_cache, data, data_len);

return ret;
}
--
2.34.1