On Thu, Nov 13, 2025 at 02:58:31PM +0100, Thorsten Blum wrote: > Determine 'key_name' before allocating memory for 'derived_buf' to only > allocate as many bytes as needed. Currently, we potentially allocate one > more byte than necessary when 'key_name' is "ENC_KEY". > > strcpy() is deprecated and uses an additional strlen() internally; use > memcpy() directly to copy 'key_name' since we already know its length > and that it is guaranteed to be NUL-terminated. > > Also reuse 'key_name_len' when copying 'master_key' instead of calling > strlen() again. > > Link: https://github.com/KSPP/linux/issues/88 > Signed-off-by: Thorsten Blum <[email protected]> > --- > security/keys/encrypted-keys/encrypted.c | 22 +++++++++------------- > 1 file changed, 9 insertions(+), 13 deletions(-) > > diff --git a/security/keys/encrypted-keys/encrypted.c > b/security/keys/encrypted-keys/encrypted.c > index 15841466b5d4..b16a5b8b935b 100644 > --- a/security/keys/encrypted-keys/encrypted.c > +++ b/security/keys/encrypted-keys/encrypted.c > @@ -12,6 +12,7 @@ > */ > > #include <linux/uaccess.h> > +#include <linux/minmax.h> > #include <linux/module.h> > #include <linux/init.h> > #include <linux/slab.h> > @@ -330,23 +331,18 @@ static int get_derived_key(u8 *derived_key, enum > derived_key_type key_type, > const u8 *master_key, size_t master_keylen) > { > u8 *derived_buf; > - unsigned int derived_buf_len; > - > - derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen; > - if (derived_buf_len < HASH_SIZE) > - derived_buf_len = HASH_SIZE; > + size_t derived_buf_len; > + const char *key_name; > + size_t key_name_len; > > + key_name = key_type ? "AUTH_KEY" : "ENC_KEY"; > + key_name_len = strlen(key_name) + 1; > + derived_buf_len = max(key_name_len + master_keylen, HASH_SIZE); > derived_buf = kzalloc(derived_buf_len, GFP_KERNEL); > if (!derived_buf) > return -ENOMEM; > - > - if (key_type) > - strcpy(derived_buf, "AUTH_KEY"); > - else > - strcpy(derived_buf, "ENC_KEY"); > - > - memcpy(derived_buf + strlen(derived_buf) + 1, master_key, > - master_keylen); > + memcpy(derived_buf, key_name, key_name_len); > + memcpy(derived_buf + key_name_len, master_key, master_keylen); > sha256(derived_buf, derived_buf_len, derived_key); > kfree_sensitive(derived_buf); > return 0;
This changes the resulting derived key when key_type == 0 && master_keylen >= 24, because different bytes are passed to sha256(). - Eric
