efi_loader: add sha384/512 on certificate revocation

Currently we don't support sha384/512 for the X.509 certificate
in dbx.  Moreover if we come across such a hash we skip the check
and approve the image,  although the image might needs to be rejected.

Rework the code a bit and fix it by adding an array of structs with the
supported GUIDs, len and literal used in the U-Boot crypto APIs instead
of hardcoding the GUID types.

It's worth noting here that efi_hash_regions() can now be reused from
efi_signature_lookup_digest() and add sha348/512 support there as well

Signed-off-by: Ilias Apalodimas <[email protected]>

include/efi_api.h

@@ -1873,6 +1873,12 @@ struct efi_system_resource_table {
 #define EFI_CERT_X509_SHA256_GUID \
 	EFI_GUID(0x3bd2a492, 0x96c0, 0x4079, 0xb4, 0x20, \
 		 0xfc, 0xf9, 0x8e, 0xf1, 0x03, 0xed)
+#define EFI_CERT_X509_SHA384_GUID \
+	EFI_GUID(0x7076876e, 0x80c2, 0x4ee6,		\
+		 0xaa, 0xd2, 0x28, 0xb3, 0x49, 0xa6, 0x86, 0x5b)
+#define EFI_CERT_X509_SHA512_GUID \
+	EFI_GUID(0x446dbf63, 0x2502, 0x4cda,		\
+		 0xbc, 0xfa, 0x24, 0x65, 0xd2, 0xb0, 0xfe, 0x9d)
 #define EFI_CERT_TYPE_PKCS7_GUID \
 	EFI_GUID(0x4aafd29d, 0x68df, 0x49ee, 0x8a, 0xa9, \
 		 0x34, 0x7d, 0x37, 0x56, 0x65, 0xa7)

include/efi_loader.h

@@ -300,6 +300,8 @@ extern const efi_guid_t efi_guid_image_security_database;
 extern const efi_guid_t efi_guid_sha256;
 extern const efi_guid_t efi_guid_cert_x509;
 extern const efi_guid_t efi_guid_cert_x509_sha256;
+extern const efi_guid_t efi_guid_cert_x509_sha384;
+extern const efi_guid_t efi_guid_cert_x509_sha512;
 extern const efi_guid_t efi_guid_cert_type_pkcs7;
 
 /* GUID of RNG protocol */
@@ -677,6 +679,10 @@ efi_status_t efi_file_size(struct efi_file_handle *fh, efi_uintn_t *size);
 /* get a device path from a Boot#### option */
 struct efi_device_path *efi_get_dp_from_boot(const efi_guid_t guid);
 
+/* get len, string (used in u-boot crypto from a guid */
+const char *guid_to_sha_str(const efi_guid_t *guid);
+int algo_to_len(const char *algo);
+
 /**
  * efi_size_in_pages() - convert size in bytes to size in pages
  *

lib/efi_loader/efi_helper.c

@@ -92,3 +92,69 @@ struct efi_device_path *efi_get_dp_from_boot(const efi_guid_t guid)
 	free(var_value);
 	return NULL;
 }
+
+const struct guid_to_hash_map {
+	efi_guid_t guid;
+	const char algo[32];
+	u32 bits;
+} guid_to_hash[] = {
+	{
+		EFI_CERT_X509_SHA256_GUID,
+		"sha256",
+		SHA256_SUM_LEN * 8,
+	},
+	{
+		EFI_CERT_SHA256_GUID,
+		"sha256",
+		SHA256_SUM_LEN * 8,
+	},
+	{
+		EFI_CERT_X509_SHA384_GUID,
+		"sha384",
+		SHA384_SUM_LEN * 8,
+	},
+	{
+		EFI_CERT_X509_SHA512_GUID,
+		"sha512",
+		SHA512_SUM_LEN * 8,
+	},
+};
+
+#define MAX_GUID_TO_HASH_COUNT ARRAY_SIZE(guid_to_hash)
+
+/** guid_to_sha_str - return the sha string e.g "sha256" for a given guid
+ *                    used on EFI security databases
+ *
+ * @guid: guid to check
+ *
+ * Return: len or 0 if no match is found
+ */
+const char *guid_to_sha_str(const efi_guid_t *guid)
+{
+	size_t i;
+
+	for (i = 0; i < MAX_GUID_TO_HASH_COUNT; i++) {
+		if (!guidcmp(guid, &guid_to_hash[i].guid))
+			return guid_to_hash[i].algo;
+	}
+
+	return NULL;
+}
+
+/** algo_to_len - return the sha size in bytes for a given string
+ *
+ * @algo: string indicating hashing algorithm to check
+ *
+ * Return: length of hash in bytes or 0 if no match is found
+ */
+int algo_to_len(const char *algo)
+{
+	size_t i;
+
+	for (i = 0; i < MAX_GUID_TO_HASH_COUNT; i++) {
+		if (!strcmp(algo, guid_to_hash[i].algo))
+			return guid_to_hash[i].bits / 8;
+	}
+
+	return 0;
+}

lib/efi_loader/efi_signature.c

@@ -24,6 +24,8 @@ const efi_guid_t efi_guid_sha256 = EFI_CERT_SHA256_GUID;
 const efi_guid_t efi_guid_cert_rsa2048 = EFI_CERT_RSA2048_GUID;
 const efi_guid_t efi_guid_cert_x509 = EFI_CERT_X509_GUID;
 const efi_guid_t efi_guid_cert_x509_sha256 = EFI_CERT_X509_SHA256_GUID;
+const efi_guid_t efi_guid_cert_x509_sha384 = EFI_CERT_X509_SHA384_GUID;
+const efi_guid_t efi_guid_cert_x509_sha512 = EFI_CERT_X509_SHA512_GUID;
 const efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;
 
 static u8 pkcs7_hdr[] = {
@@ -124,23 +126,35 @@ struct pkcs7_message *efi_parse_pkcs7_header(const void *buf,
  * Return:	true on success, false on error
  */
 static bool efi_hash_regions(struct image_region *regs, int count,
-			     void **hash, size_t *size)
+			     void **hash, const char *hash_algo, int *len)
 {
+	int ret, hash_len;
+
+	if (!hash_algo)
+		return false;
+
+	hash_len = algo_to_len(hash_algo);
+	if (!hash_len)
+		return false;
+
 	if (!*hash) {
-		*hash = calloc(1, SHA256_SUM_LEN);
+		*hash = calloc(1, hash_len);
 		if (!*hash) {
 			EFI_PRINT("Out of memory\n");
 			return false;
 		}
 	}
-	if (size)
-		*size = SHA256_SUM_LEN;
 
-	hash_calculate("sha256", regs, count, *hash);
+	ret = hash_calculate(hash_algo, regs, count, *hash);
+	if (ret)
+		return false;
+
+	if (len)
+		*len = hash_len;
 #ifdef DEBUG
 	EFI_PRINT("hash calculated:\n");
 	print_hex_dump("    ", DUMP_PREFIX_OFFSET, 16, 1,
-		       *hash, SHA256_SUM_LEN, false);
+		       *hash, hash_len, false);
 #endif
 
 	return true;
@@ -190,7 +204,6 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
 	struct efi_signature_store *siglist;
 	struct efi_sig_data *sig_data;
 	void *hash = NULL;
-	size_t size = 0;
 	bool found = false;
 	bool hash_done = false;
 
@@ -200,6 +213,8 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
 		goto out;
 
 	for (siglist = db; siglist; siglist = siglist->next) {
+		int len = 0;
+		const char *hash_algo = NULL;
 		/*
 		 * if the hash algorithm is unsupported and we get an entry in
 		 * dbx reject the image
@@ -215,8 +230,14 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
 		if (guidcmp(&siglist->sig_type, &efi_guid_sha256))
 			continue;
 
+		hash_algo = guid_to_sha_str(&efi_guid_sha256);
+		/*
+		 * We could check size and hash_algo but efi_hash_regions()
+		 * will do that for us
+		 */
 		if (!hash_done &&
-		    !efi_hash_regions(regs->reg, regs->num, &hash, &size)) {
+		    !efi_hash_regions(regs->reg, regs->num, &hash, hash_algo,
+				      &len)) {
 			EFI_PRINT("Digesting an image failed\n");
 			break;
 		}
@@ -229,8 +250,8 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
 			print_hex_dump("    ", DUMP_PREFIX_OFFSET, 16, 1,
 				       sig_data->data, sig_data->size, false);
 #endif
-			if (sig_data->size == size &&
-			    !memcmp(sig_data->data, hash, size)) {
+			if (sig_data->size == len &&
+			    !memcmp(sig_data->data, hash, len)) {
 				found = true;
 				free(hash);
 				goto out;
@@ -263,8 +284,9 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
 	struct efi_sig_data *sig_data;
 	struct image_region reg[1];
 	void *hash = NULL, *hash_tmp = NULL;
-	size_t size = 0;
+	int len = 0;
 	bool found = false;
+	const char *hash_algo = NULL;
 
 	EFI_PRINT("%s: Enter, %p, %p\n", __func__, cert, db);
 
@@ -278,7 +300,10 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
 	/* calculate hash of TBSCertificate */
 	reg[0].data = cert->tbs;
 	reg[0].size = cert->tbs_size;
-	if (!efi_hash_regions(reg, 1, &hash, &size))
+
+	/* We just need any sha256 algo to start the matching */
+	hash_algo = guid_to_sha_str(&efi_guid_sha256);
+	if (!efi_hash_regions(reg, 1, &hash, hash_algo, &len))
 		goto out;
 
 	EFI_PRINT("%s: searching for %s\n", __func__, cert->subject);
@@ -300,12 +325,13 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
 				  cert_tmp->subject);
 			reg[0].data = cert_tmp->tbs;
 			reg[0].size = cert_tmp->tbs_size;
-			if (!efi_hash_regions(reg, 1, &hash_tmp, NULL))
+			if (!efi_hash_regions(reg, 1, &hash_tmp, hash_algo,
+					      NULL))
 				goto out;
 
 			x509_free_certificate(cert_tmp);
 
-			if (!memcmp(hash, hash_tmp, size)) {
+			if (!memcmp(hash, hash_tmp, len)) {
 				found = true;
 				goto out;
 			}
@@ -400,9 +426,10 @@ static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
 	struct efi_sig_data *sig_data;
 	struct image_region reg[1];
 	void *hash = NULL;
-	size_t size = 0;
+	int len = 0;
 	time64_t revoc_time;
 	bool revoked = false;
+	const char *hash_algo = NULL;
 
 	EFI_PRINT("%s: Enter, %p, %p, %p\n", __func__, sinfo, cert, dbx);
 
@@ -411,13 +438,14 @@ static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
 
 	EFI_PRINT("Checking revocation against %s\n", cert->subject);
 	for (siglist = dbx; siglist; siglist = siglist->next) {
-		if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509_sha256))
+		hash_algo = guid_to_sha_str(&siglist->sig_type);
+		if (!hash_algo)
 			continue;
 
 		/* calculate hash of TBSCertificate */
 		reg[0].data = cert->tbs;
 		reg[0].size = cert->tbs_size;
-		if (!efi_hash_regions(reg, 1, &hash, &size))
+		if (!efi_hash_regions(reg, 1, &hash, hash_algo, &len))
 			goto out;
 
 		for (sig_data = siglist->sig_data_list; sig_data;
@@ -429,18 +457,18 @@ static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
 			 * };
 			 */
 #ifdef DEBUG
-			if (sig_data->size >= size) {
+			if (sig_data->size >= len) {
 				EFI_PRINT("hash in db:\n");
 				print_hex_dump("    ", DUMP_PREFIX_OFFSET,
 					       16, 1,
-					       sig_data->data, size, false);
+					       sig_data->data, len, false);
 			}
 #endif
-			if ((sig_data->size < size + sizeof(time64_t)) ||
-			    memcmp(sig_data->data, hash, size))
+			if ((sig_data->size < len + sizeof(time64_t)) ||
+			    memcmp(sig_data->data, hash, len))
 				continue;
 
-			memcpy(&revoc_time, sig_data->data + size,
+			memcpy(&revoc_time, sig_data->data + len,
 			       sizeof(revoc_time));
 			EFI_PRINT("revocation time: 0x%llx\n", revoc_time);
 			/*
@@ -500,7 +528,9 @@ bool efi_signature_verify(struct efi_image_regions *regs,
 		 */
 		if (!msg->data &&
 		    !efi_hash_regions(regs->reg, regs->num,
-				      (void **)&sinfo->sig->digest, NULL)) {
+				      (void **)&sinfo->sig->digest,
+				      guid_to_sha_str(&efi_guid_sha256),
+				      NULL)) {
 			EFI_PRINT("Digesting an image failed\n");
 			goto out;
 		}