1 files changed, 299 insertions, 0 deletions
diff --git a/lib/crypto_backend/crypto_storage.c b/lib/crypto_backend/crypto_storage.c
new file mode 100644
index 0000000..16a20b1
--- /dev/null
+++ b/lib/crypto_backend/crypto_storage.c
@@ -0,0 +1,299 @@
+/*
+ * Generic wrapper for storage encryption modes and Initial Vectors
+ * (reimplementation of some functions from Linux dm-crypt kernel)
+ *
+ * Copyright (C) 2014-2019 Milan Broz
+ *
+ * This file is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this file; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdlib.h>
+#include <errno.h>
+#include "bitops.h"
+#include "crypto_backend.h"
+
+#define SECTOR_SHIFT	9
+#define SECTOR_SIZE	(1 << SECTOR_SHIFT)
+
+/*
+ * Internal IV helper
+ * IV documentation: https://gitlab.com/cryptsetup/cryptsetup/wikis/DMCrypt
+ */
+struct crypt_sector_iv {
+	enum { IV_NONE, IV_NULL, IV_PLAIN, IV_PLAIN64, IV_ESSIV, IV_BENBI, IV_PLAIN64BE } type;
+	int iv_size;
+	char *iv;
+	struct crypt_cipher *essiv_cipher;
+	int benbi_shift;
+};
+
+/* Block encryption storage context */
+struct crypt_storage {
+	uint64_t sector_start;
+	struct crypt_cipher *cipher;
+	struct crypt_sector_iv cipher_iv;
+};
+
+static int int_log2(unsigned int x)
+{
+	int r = 0;
+	for (x >>= 1; x > 0; x >>= 1)
+		r++;
+	return r;
+}
+
+static int crypt_sector_iv_init(struct crypt_sector_iv *ctx,
+			 const char *cipher_name, const char *mode_name,
+			 const char *iv_name, const void *key, size_t key_length)
+{
+	memset(ctx, 0, sizeof(*ctx));
+
+	ctx->iv_size = crypt_cipher_ivsize(cipher_name, mode_name);
+	if (ctx->iv_size < 8)
+		return -ENOENT;
+
+	if (!strcmp(cipher_name, "cipher_null") ||
+	    !strcmp(mode_name, "ecb")) {
+		if (iv_name)
+			return -EINVAL;
+		ctx->type = IV_NONE;
+		ctx->iv_size = 0;
+		return 0;
+	} else if (!iv_name) {
+		return -EINVAL;
+	} else if (!strcasecmp(iv_name, "null")) {
+		ctx->type = IV_NULL;
+	} else if (!strcasecmp(iv_name, "plain64")) {
+		ctx->type = IV_PLAIN64;
+	} else if (!strcasecmp(iv_name, "plain64be")) {
+		ctx->type = IV_PLAIN64BE;
+	} else if (!strcasecmp(iv_name, "plain")) {
+		ctx->type = IV_PLAIN;
+	} else if (!strncasecmp(iv_name, "essiv:", 6)) {
+		struct crypt_hash *h = NULL;
+		char *hash_name = strchr(iv_name, ':');
+		int hash_size;
+		char tmp[256];
+		int r;
+
+		if (!hash_name)
+			return -EINVAL;
+
+		hash_size = crypt_hash_size(++hash_name);
+		if (hash_size < 0)
+			return -ENOENT;
+
+		if ((unsigned)hash_size > sizeof(tmp))
+			return -EINVAL;
+
+		if (crypt_hash_init(&h, hash_name))
+			return -EINVAL;
+
+		r = crypt_hash_write(h, key, key_length);
+		if (r) {
+			crypt_hash_destroy(h);
+			return r;
+		}
+
+		r = crypt_hash_final(h, tmp, hash_size);
+		crypt_hash_destroy(h);
+		if (r) {
+			crypt_backend_memzero(tmp, sizeof(tmp));
+			return r;
+		}
+
+		r = crypt_cipher_init(&ctx->essiv_cipher, cipher_name, "ecb",
+				      tmp, hash_size);
+		crypt_backend_memzero(tmp, sizeof(tmp));
+		if (r)
+			return r;
+
+		ctx->type = IV_ESSIV;
+	} else if (!strncasecmp(iv_name, "benbi", 5)) {
+		int log = int_log2(ctx->iv_size);
+		if (log > SECTOR_SHIFT)
+			return -EINVAL;
+
+		ctx->type = IV_BENBI;
+		ctx->benbi_shift = SECTOR_SHIFT - log;
+	} else
+		return -ENOENT;
+
+	ctx->iv = malloc(ctx->iv_size);
+	if (!ctx->iv)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int crypt_sector_iv_generate(struct crypt_sector_iv *ctx, uint64_t sector)
+{
+	uint64_t val;
+
+	switch (ctx->type) {
+	case IV_NONE:
+		break;
+	case IV_NULL:
+		memset(ctx->iv, 0, ctx->iv_size);
+		break;
+	case IV_PLAIN:
+		memset(ctx->iv, 0, ctx->iv_size);
+		*(uint32_t *)ctx->iv = cpu_to_le32(sector & 0xffffffff);
+		break;
+	case IV_PLAIN64:
+		memset(ctx->iv, 0, ctx->iv_size);
+		*(uint64_t *)ctx->iv = cpu_to_le64(sector);
+		break;
+	case IV_PLAIN64BE:
+		memset(ctx->iv, 0, ctx->iv_size);
+		*(uint64_t *)&ctx->iv[ctx->iv_size - sizeof(uint64_t)] = cpu_to_be64(sector);
+		break;
+	case IV_ESSIV:
+		memset(ctx->iv, 0, ctx->iv_size);
+		*(uint64_t *)ctx->iv = cpu_to_le64(sector);
+		return crypt_cipher_encrypt(ctx->essiv_cipher,
+			ctx->iv, ctx->iv, ctx->iv_size, NULL, 0);
+		break;
+	case IV_BENBI:
+		memset(ctx->iv, 0, ctx->iv_size);
+		val = cpu_to_be64((sector << ctx->benbi_shift) + 1);
+		memcpy(ctx->iv + ctx->iv_size - sizeof(val), &val, sizeof(val));
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void crypt_sector_iv_destroy(struct crypt_sector_iv *ctx)
+{
+	if (ctx->type == IV_ESSIV)
+		crypt_cipher_destroy(ctx->essiv_cipher);
+
+	if (ctx->iv) {
+		memset(ctx->iv, 0, ctx->iv_size);
+		free(ctx->iv);
+	}
+
+	memset(ctx, 0, sizeof(*ctx));
+}
+
+/* Block encryption storage wrappers */
+
+int crypt_storage_init(struct crypt_storage **ctx,
+		       uint64_t sector_start,
+		       const char *cipher,
+		       const char *cipher_mode,
+		       const void *key, size_t key_length)
+{
+	struct crypt_storage *s;
+	char mode_name[64];
+	char *cipher_iv = NULL;
+	int r = -EIO;
+
+	s = malloc(sizeof(*s));
+	if (!s)
+		return -ENOMEM;
+	memset(s, 0, sizeof(*s));
+
+	/* Remove IV if present */
+	strncpy(mode_name, cipher_mode, sizeof(mode_name));
+	mode_name[sizeof(mode_name) - 1] = 0;
+	cipher_iv = strchr(mode_name, '-');
+	if (cipher_iv) {
+		*cipher_iv = '\0';
+		cipher_iv++;
+	}
+
+	r = crypt_cipher_init(&s->cipher, cipher, mode_name, key, key_length);
+	if (r) {
+		crypt_storage_destroy(s);
+		return r;
+	}
+
+	r = crypt_sector_iv_init(&s->cipher_iv, cipher, mode_name, cipher_iv, key, key_length);
+	if (r) {
+		crypt_storage_destroy(s);
+		return r;
+	}
+
+	s->sector_start = sector_start;
+
+	*ctx = s;
+	return 0;
+}
+
+int crypt_storage_decrypt(struct crypt_storage *ctx,
+		       uint64_t sector, size_t count,
+		       char *buffer)
+{
+	unsigned int i;
+	int r = 0;
+
+	for (i = 0; i < count; i++) {
+		r = crypt_sector_iv_generate(&ctx->cipher_iv, sector + i);
+		if (r)
+			break;
+		r = crypt_cipher_decrypt(ctx->cipher,
+					 &buffer[i * SECTOR_SIZE],
+					 &buffer[i * SECTOR_SIZE],
+					 SECTOR_SIZE,
+					 ctx->cipher_iv.iv,
+					 ctx->cipher_iv.iv_size);
+		if (r)
+			break;
+	}
+
+	return r;
+}
+
+int crypt_storage_encrypt(struct crypt_storage *ctx,
+		       uint64_t sector, size_t count,
+		       char *buffer)
+{
+	unsigned int i;
+	int r = 0;
+
+	for (i = 0; i < count; i++) {
+		r = crypt_sector_iv_generate(&ctx->cipher_iv, sector + i);
+		if (r)
+			break;
+		r = crypt_cipher_encrypt(ctx->cipher,
+					 &buffer[i * SECTOR_SIZE],
+					 &buffer[i * SECTOR_SIZE],
+					 SECTOR_SIZE,
+					 ctx->cipher_iv.iv,
+					 ctx->cipher_iv.iv_size);
+		if (r)
+			break;
+	}
+
+	return r;
+}
+
+void crypt_storage_destroy(struct crypt_storage *ctx)
+{
+	if (!ctx)
+		return;
+
+	crypt_sector_iv_destroy(&ctx->cipher_iv);
+
+	if (ctx->cipher)
+		crypt_cipher_destroy(ctx->cipher);
+
+	memset(ctx, 0, sizeof(*ctx));
+	free(ctx);
+}