From 2a559a8bdeae853b6a8abb477c88875e1d4de591 Mon Sep 17 00:00:00 2001 From: Colin Ian King Date: Mon, 23 Feb 2015 11:34:10 +0000 Subject: [PATCH] eCryptfs: ensure copy to crypt_stat->cipher does not overrun The patch 237fead61998: "[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 Reported-by: Dan Carpenter [tyhicks: Added the NOTE about the overflow not being triggerable] Signed-off-by: Tyler Hicks --- fs/ecryptfs/ecryptfs_kernel.h | 4 ++-- fs/ecryptfs/keystore.c | 2 +- fs/ecryptfs/main.c | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h index 90d1882b306f..5ba029e627cc 100644 --- a/fs/ecryptfs/ecryptfs_kernel.h +++ b/fs/ecryptfs/ecryptfs_kernel.h @@ -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; diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c index 917bd5c9776a..6bd67e2011f0 100644 --- a/fs/ecryptfs/keystore.c +++ b/fs/ecryptfs/keystore.c @@ -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]; }; /** diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index 1895d60f4122..c095d3264259 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -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); } -- 2.20.1