[PATCH next] keys: Replace strcpy(derived_buf, "AUTH_KEY") with strscpy(..., HASH_SIZE)

[PATCH next] keys: Replace strcpy(derived_buf, "AUTH_KEY") with strscpy(..., HASH_SIZE)

[david.laight.linux]

From: David Laight <david.laight.linux@gmail.com>

derived_buf is guaranteed to be HASH_SIZE - and it is more than enough.
The strscpy() degenerates into an memcpy() (as did the strcpy()).
Do the same for the associated "ENC_KEY" copy.

Removes a possibly unbounded strcpy().

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
This is one of a group of patches that remove potentially unbounded
strcpy() calls.

They are mostly replaced by strscpy() or, when strlen() has just been
called, with memcpy() (usually including the '\0').

Calls with copy string literals into arrays are left unchanged.
They are safe and easily detected as such.

The changes were made by getting the compiler to detect the calls and
then fixing the code by hand.

Note that all the changes are only compile tested.

Some Makefiles were changed to allow files to contain strcpy().
As well as 'difficult to fix' files, this included 'show' functions
as they really need to use sysfs_emit() or seq_printf().

All the patches are being sent individually to avoid very long cc lists.
Apologies for the terse commit messages and likely unexpected tags.
(There are about 100 patches in total.)

 security/keys/encrypted-keys/encrypted.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 56b531587a1e..59cb77b237b3 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -343,9 +343,9 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 		return -ENOMEM;
 
 	if (key_type)
-		strcpy(derived_buf, "AUTH_KEY");
+		strscpy(derived_buf, "AUTH_KEY", HASH_SIZE);
 	else
-		strcpy(derived_buf, "ENC_KEY");
+		strscpy(derived_buf, "ENC_KEY", HASH_SIZE);
 
 	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 	       master_keylen);
-- 
2.39.5

Re: [PATCH next] keys: Replace strcpy(derived_buf, "AUTH_KEY") with strscpy(..., HASH_SIZE)

[Jarkko Sakkinen]

On Sat, Jun 06, 2026 at 09:26:03PM +0100, david.laight.linux@gmail.com wrote:
> From: David Laight <david.laight.linux@gmail.com>
> 
> derived_buf is guaranteed to be HASH_SIZE - and it is more than enough.
> The strscpy() degenerates into an memcpy() (as did the strcpy()).
> Do the same for the associated "ENC_KEY" copy.
> 
> Removes a possibly unbounded strcpy().
> 
> Signed-off-by: David Laight <david.laight.linux@gmail.com>
> ---
> This is one of a group of patches that remove potentially unbounded
> strcpy() calls.
> 
> They are mostly replaced by strscpy() or, when strlen() has just been
> called, with memcpy() (usually including the '\0').
> 
> Calls with copy string literals into arrays are left unchanged.
> They are safe and easily detected as such.
> 
> The changes were made by getting the compiler to detect the calls and
> then fixing the code by hand.
> 
> Note that all the changes are only compile tested.
> 
> Some Makefiles were changed to allow files to contain strcpy().
> As well as 'difficult to fix' files, this included 'show' functions
> as they really need to use sysfs_emit() or seq_printf().
> 
> All the patches are being sent individually to avoid very long cc lists.
> Apologies for the terse commit messages and likely unexpected tags.
> (There are about 100 patches in total.)
> 
>  security/keys/encrypted-keys/encrypted.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
> index 56b531587a1e..59cb77b237b3 100644
> --- a/security/keys/encrypted-keys/encrypted.c
> +++ b/security/keys/encrypted-keys/encrypted.c
> @@ -343,9 +343,9 @@ static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
>  		return -ENOMEM;
>  
>  	if (key_type)
> -		strcpy(derived_buf, "AUTH_KEY");
> +		strscpy(derived_buf, "AUTH_KEY", HASH_SIZE);
>  	else
> -		strcpy(derived_buf, "ENC_KEY");
> +		strscpy(derived_buf, "ENC_KEY", HASH_SIZE);
>  
>  	memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
>  	       master_keylen);
> -- 
> 2.39.5
> 

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko