1 files changed, 302 insertions, 0 deletions
diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
new file mode 100644
index 000000000..b4c23a0ed
--- /dev/null
+++ b/security/integrity/digsig_asymmetric.c
@@ -0,0 +1,302 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2013 Intel Corporation
+ *
+ * Author:
+ * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
+ */
+
+#include <linux/err.h>
+#include <linux/ratelimit.h>
+#include <linux/key-type.h>
+#include <crypto/public_key.h>
+#include <crypto/hash_info.h>
+#include <keys/asymmetric-type.h>
+#include <keys/system_keyring.h>
+
+#include "integrity.h"
+
+/*
+ * Request an asymmetric key.
+ */
+static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
+{
+	struct key *key;
+	char name[12];
+
+	sprintf(name, "id:%08x", keyid);
+
+	pr_debug("key search: \"%s\"\n", name);
+
+	key = get_ima_blacklist_keyring();
+	if (key) {
+		key_ref_t kref;
+
+		kref = keyring_search(make_key_ref(key, 1),
+				      &key_type_asymmetric, name, true);
+		if (!IS_ERR(kref)) {
+			pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
+			return ERR_PTR(-EKEYREJECTED);
+		}
+	}
+
+	if (keyring) {
+		/* search in specific keyring */
+		key_ref_t kref;
+
+		kref = keyring_search(make_key_ref(keyring, 1),
+				      &key_type_asymmetric, name, true);
+		if (IS_ERR(kref))
+			key = ERR_CAST(kref);
+		else
+			key = key_ref_to_ptr(kref);
+	} else {
+		key = request_key(&key_type_asymmetric, name, NULL);
+	}
+
+	if (IS_ERR(key)) {
+		if (keyring)
+			pr_err_ratelimited("Request for unknown key '%s' in '%s' keyring. err %ld\n",
+					   name, keyring->description,
+					   PTR_ERR(key));
+		else
+			pr_err_ratelimited("Request for unknown key '%s' err %ld\n",
+					   name, PTR_ERR(key));
+
+		switch (PTR_ERR(key)) {
+			/* Hide some search errors */
+		case -EACCES:
+		case -ENOTDIR:
+		case -EAGAIN:
+			return ERR_PTR(-ENOKEY);
+		default:
+			return key;
+		}
+	}
+
+	pr_debug("%s() = 0 [%x]\n", __func__, key_serial(key));
+
+	return key;
+}
+
+/**
+ * asymmetric_verify_common -- sigv2 and sigv3 common verify function
+ * @key: The key to use for signature verification; caller must free it
+ * @pk: The associated public key; must not be NULL
+ * @sig: The xattr signature
+ * @siglen: The length of the xattr signature; must be at least
+ *          sizeof(struct signature_v2_hdr)
+ * @data: The data to verify the signature on
+ * @datalen: Length of @data
+ */
+static int asymmetric_verify_common(const struct key *key,
+				    const struct public_key *pk,
+				    const char *sig, int siglen,
+				    const char *data, int datalen)
+{
+	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
+	struct public_key_signature pks;
+	int ret;
+
+	siglen -= sizeof(*hdr);
+
+	if (siglen != be16_to_cpu(hdr->sig_size))
+		return -EBADMSG;
+
+	if (hdr->hash_algo >= HASH_ALGO__LAST)
+		return -ENOPKG;
+
+	memset(&pks, 0, sizeof(pks));
+
+	pks.hash_algo = hash_algo_name[hdr->hash_algo];
+	pks.pkey_algo = pk->pkey_algo;
+	if (!strcmp(pk->pkey_algo, "rsa")) {
+		pks.encoding = "pkcs1";
+	} else if (!strncmp(pk->pkey_algo, "ecdsa-", 6)) {
+		/* edcsa-nist-p192 etc. */
+		pks.encoding = "x962";
+	} else if (!strcmp(pk->pkey_algo, "ecrdsa")) {
+		pks.encoding = "raw";
+	} else {
+		ret = -ENOPKG;
+		goto out;
+	}
+
+	pks.m = (u8 *)data;
+	pks.m_size = datalen;
+	pks.s = hdr->sig;
+	pks.s_size = siglen;
+	ret = verify_signature(key, &pks);
+out:
+	pr_debug("%s() = %d\n", __func__, ret);
+	return ret;
+}
+
+int asymmetric_verify(struct key *keyring, const char *sig,
+		      int siglen, const char *data, int datalen)
+{
+	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
+	const struct public_key *pk;
+	struct key *key;
+	int ret;
+
+	if (siglen <= sizeof(*hdr))
+		return -EBADMSG;
+
+	key = request_asymmetric_key(keyring, be32_to_cpu(hdr->keyid));
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+	pk = asymmetric_key_public_key(key);
+	if (!pk) {
+		ret = -ENOKEY;
+		goto out;
+	}
+
+	ret = asymmetric_verify_common(key, pk, sig, siglen, data, datalen);
+
+out:
+	key_put(key);
+
+	return ret;
+}
+
+/*
+ * calc_file_id_hash - calculate the hash of the ima_file_id struct data
+ * @type: xattr type [enum evm_ima_xattr_type]
+ * @algo: hash algorithm [enum hash_algo]; caller must ensure valid value
+ * @digest: pointer to the digest to be hashed
+ * @hash: (out) pointer to the hash
+ *
+ * IMA signature version 3 disambiguates the data that is signed by
+ * indirectly signing the hash of the ima_file_id structure data.
+ *
+ * Return 0 on success, error code otherwise.
+ */
+static int calc_file_id_hash(enum evm_ima_xattr_type type,
+			     enum hash_algo algo, const u8 *digest,
+			     struct ima_max_digest_data *hash)
+{
+	struct ima_file_id file_id = {.hash_type = type, .hash_algorithm = algo};
+	size_t digest_size = hash_digest_size[algo];
+	struct crypto_shash *tfm;
+	size_t file_id_size;
+	int rc;
+
+	if (type != IMA_VERITY_DIGSIG && type != EVM_IMA_XATTR_DIGSIG &&
+	    type != EVM_XATTR_PORTABLE_DIGSIG)
+		return -EINVAL;
+
+	tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	memcpy(file_id.hash, digest, digest_size);
+
+	/* Calculate the ima_file_id struct hash on the portion used. */
+	file_id_size = sizeof(file_id) - (HASH_MAX_DIGESTSIZE - digest_size);
+
+	hash->hdr.algo = algo;
+	hash->hdr.length = digest_size;
+	rc = crypto_shash_tfm_digest(tfm, (const u8 *)&file_id, file_id_size,
+				     hash->digest);
+
+	crypto_free_shash(tfm);
+	return rc;
+}
+
+/**
+ * asymmetric_verify_v3_hashless - Use hashless signature verification on sigv3
+ * @key: The key to use for signature verification; caller must free it
+ * @pk: The associated public key; must not be NULL
+ * @encoding: The encoding the key type uses
+ * @sig: The xattr signature
+ * @siglen: The length of the xattr signature; must be at least
+ *          sizeof(struct signature_v2_hdr)
+ * @algo: hash algorithm [enum hash_algo]; caller must ensure valid value
+ * @digest: The file digest
+ *
+ * Create an ima_file_id structure and use it for signature verification
+ * directly. This can be used for ML-DSA in pure mode for example.
+ */
+static int asymmetric_verify_v3_hashless(struct key *key,
+					 const struct public_key *pk,
+					 const char *encoding,
+					 const char *sig, int siglen,
+					 u8 algo,
+					 const u8 *digest)
+{
+	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
+	struct ima_file_id file_id = {
+		.hash_type = hdr->type,
+		.hash_algorithm = algo,
+	};
+	size_t digest_size = hash_digest_size[algo];
+	struct public_key_signature pks = {
+		.m = (u8 *)&file_id,
+		.m_size = sizeof(file_id) - (HASH_MAX_DIGESTSIZE - digest_size),
+		.s = hdr->sig,
+		.s_size = siglen - sizeof(*hdr),
+		.pkey_algo = pk->pkey_algo,
+		.hash_algo = "none",
+		.encoding = encoding,
+	};
+	int ret;
+
+	if (hdr->type != IMA_VERITY_DIGSIG &&
+	    hdr->type != EVM_IMA_XATTR_DIGSIG &&
+	    hdr->type != EVM_XATTR_PORTABLE_DIGSIG)
+		return -EINVAL;
+
+	if (pks.s_size != be16_to_cpu(hdr->sig_size))
+		return -EBADMSG;
+
+	memcpy(file_id.hash, digest, digest_size);
+
+	ret = verify_signature(key, &pks);
+	pr_debug("%s() = %d\n", __func__, ret);
+	return ret;
+}
+
+int asymmetric_verify_v3(struct key *keyring, const char *sig, int siglen,
+			 const char *data, int datalen, u8 algo)
+{
+	struct signature_v2_hdr *hdr = (struct signature_v2_hdr *)sig;
+	struct ima_max_digest_data hash;
+	const struct public_key *pk;
+	struct key *key;
+	int rc;
+
+	if (algo >= HASH_ALGO__LAST)
+		return -ENOPKG;
+
+	if (siglen <= sizeof(*hdr))
+		return -EBADMSG;
+
+	key = request_asymmetric_key(keyring, be32_to_cpu(hdr->keyid));
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	pk = asymmetric_key_public_key(key);
+	if (!pk) {
+		rc = -ENOKEY;
+		goto out;
+	}
+	if (!strncmp(pk->pkey_algo, "mldsa", 5)) {
+		rc = asymmetric_verify_v3_hashless(key, pk, "raw",
+						   sig, siglen, algo, data);
+	} else {
+		rc = calc_file_id_hash(hdr->type, algo, data, &hash);
+		if (rc) {
+			rc = -EINVAL;
+			goto out;
+		}
+
+		rc = asymmetric_verify_common(key, pk, sig, siglen, hash.digest,
+					      hash.hdr.length);
+	}
+
+out:
+	key_put(key);
+
+	return rc;
+}