strncpy() is deprecated for NUL-terminated destination buffers; use strscpy_pad() instead to retain the NUL-padding behavior of strncpy().
The destination buffer is initialized using kzalloc() with a 'signature' size of ECRYPTFS_PASSWORD_SIG_SIZE + 1. strncpy() then copies up to ECRYPTFS_PASSWORD_SIG_SIZE bytes from 'key_desc', NUL-padding any remaining bytes if needed, but expects the last byte to be zero. strscpy_pad() also copies the source string to 'signature', and NUL-pads the destination buffer if needed, but ensures it's always NUL-terminated without relying on it being zero-initialized. strscpy_pad() automatically determines the size of the fixed-length destination buffer via sizeof() when the optional size argument is omitted, making an explicit size unnecessary. In encrypted_init(), the source string 'key_desc' is validated by valid_ecryptfs_desc() before calling ecryptfs_fill_auth_tok(), and is therefore NUL-terminated and satisfies the __must_be_cstr() requirement of strscpy_pad(). Link: https://github.com/KSPP/linux/issues/90 Reviewed-by: Kees Cook <[email protected]> Reviewed-by: Jarkko Sakkinen <[email protected]> Signed-off-by: Thorsten Blum <[email protected]> --- Changes in v3: - Improve commit message - Link to v2: https://lore.kernel.org/lkml/[email protected]/ Changes in v2: - Improve commit message as suggested by Jarkko and Kees - Link to v1: https://lore.kernel.org/lkml/[email protected]/ --- security/keys/encrypted-keys/ecryptfs_format.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/security/keys/encrypted-keys/ecryptfs_format.c b/security/keys/encrypted-keys/ecryptfs_format.c index 8fdd76105ce3..2fc6f3a66135 100644 --- a/security/keys/encrypted-keys/ecryptfs_format.c +++ b/security/keys/encrypted-keys/ecryptfs_format.c @@ -54,8 +54,7 @@ int ecryptfs_fill_auth_tok(struct ecryptfs_auth_tok *auth_tok, auth_tok->version = (((uint16_t)(major << 8) & 0xFF00) | ((uint16_t)minor & 0x00FF)); auth_tok->token_type = ECRYPTFS_PASSWORD; - strncpy((char *)auth_tok->token.password.signature, key_desc, - ECRYPTFS_PASSWORD_SIG_SIZE); + strscpy_pad(auth_tok->token.password.signature, key_desc); auth_tok->token.password.session_key_encryption_key_bytes = ECRYPTFS_MAX_KEY_BYTES; /* -- 2.51.0
