eCryptfs: ensure copy to crypt_stat->cipher does not overrun (2a559a8b) · Commits · 戴 / test

The patch : "[PATCH] ecryptfs: fs/Makefile and fs/Kconfig" from Oct 4, 2006, leads to the following static checker warning: fs/ecryptfs/crypto.c:846 ecryptfs_new_file_context() error: off-by-one overflow 'crypt_stat->cipher' size 32. rl = '0-32' There is a mismatch between the size of ecryptfs_crypt_stat.cipher and ecryptfs_mount_crypt_stat.global_default_cipher_name causing the copy of the cipher name to cause a off-by-one string copy error. This fix ensures the space reserved for this string is the same size including the trailing zero at the end throughout ecryptfs. This fix avoids increasing the size of ecryptfs_crypt_stat.cipher and also ecryptfs_parse_tag_70_packet_silly_stack.cipher_string and instead reduces the of ECRYPTFS_MAX_CIPHER_NAME_SIZE to 31 and includes the + 1 for the end of string terminator. NOTE: An overflow is not possible in practice since the value copied into global_default_cipher_name is validated by ecryptfs_code_for_cipher_string() at mount time. None of the allowed cipher strings are long enough to cause the potential buffer overflow fixed by this patch. Signed-off-by:

Colin Ian King <colin.king@canonical.com> Reported-by:

Dan Carpenter <dan.carpenter@oracle.com> [tyhicks: Added the NOTE about the overflow not being triggerable] Signed-off-by:

Tyler Hicks <tyhicks@canonical.com>

fs/ecryptfs/ecryptfs_kernel.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -124,7 +124,7 @@ ecryptfs_get_key_payload_data(struct key *key)
		}

		#define ECRYPTFS_MAX_KEYSET_SIZE 1024
		#define ECRYPTFS_MAX_CIPHER_NAME_SIZE 32
		#define ECRYPTFS_MAX_CIPHER_NAME_SIZE 31
		#define ECRYPTFS_MAX_NUM_ENC_KEYS 64
		#define ECRYPTFS_MAX_IV_BYTES 16 /* 128 bits */
		#define ECRYPTFS_SALT_BYTES 2
		@@ -237,7 +237,7 @@ struct ecryptfs_crypt_stat {
		struct crypto_ablkcipher *tfm;
		struct crypto_hash hash_tfm; / Crypto context for generating
		* the initialization vectors */
		unsigned char cipher[ECRYPTFS_MAX_CIPHER_NAME_SIZE];
		unsigned char cipher[ECRYPTFS_MAX_CIPHER_NAME_SIZE + 1];
		unsigned char key[ECRYPTFS_MAX_KEY_BYTES];
		unsigned char root_iv[ECRYPTFS_MAX_IV_BYTES];
		struct list_head keysig_list;

fs/ecryptfs/keystore.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -891,7 +891,7 @@ struct ecryptfs_parse_tag_70_packet_silly_stack {
		struct blkcipher_desc desc;
		char fnek_sig_hex[ECRYPTFS_SIG_SIZE_HEX + 1];
		char iv[ECRYPTFS_MAX_IV_BYTES];
		char cipher_string[ECRYPTFS_MAX_CIPHER_NAME_SIZE];
		char cipher_string[ECRYPTFS_MAX_CIPHER_NAME_SIZE + 1];
		};

		/**

fs/ecryptfs/main.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -407,7 +407,7 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info sbi, char options,
		if (!cipher_name_set) {
		int cipher_name_len = strlen(ECRYPTFS_DEFAULT_CIPHER);

		BUG_ON(cipher_name_len >= ECRYPTFS_MAX_CIPHER_NAME_SIZE);
		BUG_ON(cipher_name_len > ECRYPTFS_MAX_CIPHER_NAME_SIZE);
		strcpy(mount_crypt_stat->global_default_cipher_name,
		ECRYPTFS_DEFAULT_CIPHER);
		}

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