[v1] keys: Replace deprecated strncpy in ecryptfs_fill_auth_tok

[PATCH] keys: Replace deprecated strncpy in ecryptfs_fill_auth_tok

Posted by Thorsten Blum 2 months, 1 week ago

strncpy() is deprecated for NUL-terminated destination buffers; use
strscpy_pad() instead.

Link: https://github.com/KSPP/linux/issues/90
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 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

Re: [PATCH] keys: Replace deprecated strncpy in ecryptfs_fill_auth_tok

Posted by Kees Cook 2 months, 1 week ago

On Thu, Oct 09, 2025 at 08:03:17PM +0200, Thorsten Blum wrote:
> strncpy() is deprecated for NUL-terminated destination buffers; use
> strscpy_pad() instead.

Remember for strncpy->strscpy conversions, the commit message needs
to include:

- how did you determine this was a NUL-terminated destination?
- how did you determine the need for padding or not?
- how do you know that final byte truncation is not a problem?

-Kees

> 
> Link: https://github.com/KSPP/linux/issues/90
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>  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
> 
> 

-- 
Kees Cook

Re: [PATCH] keys: Replace deprecated strncpy in ecryptfs_fill_auth_tok

Posted by Jarkko Sakkinen 2 months, 1 week ago

On Thu, Oct 09, 2025 at 08:03:17PM +0200, Thorsten Blum wrote:
> strncpy() is deprecated for NUL-terminated destination buffers; use
> strscpy_pad() instead.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>

Deprecated or not but commit message still should have a better
explanation :-) Sure there's also the link too that explains it 
all but still one should get the gist without cross-referencing
into it.

It's a permanent amortized cost as everytime when revisiting this
commit (e.g. over the course of bisecting or whatever), you need
a web browser in order to make anything out of the message.

> ---
>  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
> 

BR, Jarkko