[PATCH v2 07/15] ima: add parser of compact digest list

[Roberto Sassu]

This patch introduces the parser for the compact digest list.
Its format is:

entry_id[2] count[4] data_len[4]
data[data_len]
entry_id[2] count[4] data_len[4]
data[data_len]
...

entry_id, count and data_len are in little endian.

This format is suitable to store a large number of digests, as there is no
metadata provided for each. Digests (which have all the same size) are
concatenated together and placed after the header.

COMPACT_DIGEST (0) and COMPACT_DIGEST_MUTABLE (1) entry IDs are supported.

If the entry ID is COMPACT_DIGEST and appraisal is in enforcing mode, file
updates are denied. If the entry ID is COMPACT_DIGEST_MUTABLE, file updates
are permitted.

Changelog

v1:
- Renamed COMPACT_LIST_ID_DIGEST to COMPACT_DIGEST
- Added support for immutable/mutable files

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
 security/integrity/ima/ima_digest_list.c | 66 ++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/security/integrity/ima/ima_digest_list.c b/security/integrity/ima/ima_digest_list.c
index 28172424e5a2..6ad00ba32c94 100644
--- a/security/integrity/ima/ima_digest_list.c
+++ b/security/integrity/ima/ima_digest_list.c
@@ -23,6 +23,69 @@ enum digest_metadata_fields {DATA_ALGO, DATA_DIGEST, DATA_SIGNATURE,
 			     DATA_FILE_PATH, DATA_REF_ID, DATA_TYPE,
 			     DATA__LAST};
 
+enum digest_data_types {DATA_TYPE_COMPACT_LIST};
+
+enum compact_list_entry_ids {COMPACT_DIGEST, COMPACT_DIGEST_MUTABLE};
+
+struct compact_list_hdr {
+	u16 entry_id;
+	u32 count;
+	u32 datalen;
+} __packed;
+
+static int ima_parse_compact_list(loff_t size, void *buf)
+{
+	void *bufp = buf, *bufendp = buf + size;
+	int digest_len = hash_digest_size[ima_hash_algo];
+	struct compact_list_hdr *hdr;
+	u8 is_mutable = 0;
+	int ret, i;
+
+	while (bufp < bufendp) {
+		if (bufp + sizeof(*hdr) > bufendp) {
+			pr_err("compact list, missing header\n");
+			return -EINVAL;
+		}
+
+		hdr = bufp;
+
+		if (ima_canonical_fmt) {
+			hdr->entry_id = le16_to_cpu(hdr->entry_id);
+			hdr->count = le32_to_cpu(hdr->count);
+			hdr->datalen = le32_to_cpu(hdr->datalen);
+		}
+
+		switch (hdr->entry_id) {
+		case COMPACT_DIGEST_MUTABLE:
+			is_mutable = 1;
+		case COMPACT_DIGEST:
+			break;
+		default:
+			pr_err("compact list, invalid data type\n");
+			return -EINVAL;
+		}
+
+		bufp += sizeof(*hdr);
+
+		for (i = 0; i < hdr->count &&
+		     bufp + digest_len <= bufendp; i++) {
+			ret = ima_add_digest_data_entry(bufp, is_mutable);
+			if (ret < 0 && ret != -EEXIST)
+				return ret;
+
+			bufp += digest_len;
+		}
+
+		if (i != hdr->count ||
+		    bufp != (void *)hdr + sizeof(*hdr) + hdr->datalen) {
+			pr_err("compact list, invalid data\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 static int ima_parse_digest_list_data(struct ima_field_data *data)
 {
 	void *digest_list;
@@ -47,6 +110,9 @@ static int ima_parse_digest_list_data(struct ima_field_data *data)
 	}
 
 	switch (data_type) {
+	case DATA_TYPE_COMPACT_LIST:
+		ret = ima_parse_compact_list(digest_list_size, digest_list);
+		break;
 	default:
 		pr_err("Parser for data type %d not implemented\n", data_type);
 		ret = -EINVAL;
-- 
2.11.0