On Tue, Apr 16, 2024 at 07:14:28PM +0000, Mothershead, Hailey wrote: > > On 4/15/24, 3:50 PM, "Eric Biggers" <ebiggers@xxxxxxxxxx <mailto:ebiggers@xxxxxxxxxx>> wrote: > > > > On Mon, Apr 15, 2024 at 10:19:15PM +0000, Hailey Mothershead wrote: > > > I.G 9.7.B for FIPS 140-3 specifies that variables temporarily holding > > > cryptographic information should be zeroized once they are no longer > > > needed. Accomplish this by using kfree_sensitive for buffers that > > > previously held the private key. > > > > > > Signed-off-by: Hailey Mothershead <hailmo@xxxxxxxxxx <mailto:hailmo@xxxxxxxxxx>> > > > --- > > > crypto/aead.c | 3 +-- > > > crypto/cipher.c | 3 +-- > > > 2 files changed, 2 insertions(+), 4 deletions(-) > > > > > > diff --git a/crypto/aead.c b/crypto/aead.c > > > index 16991095270d..c4ece86c45bc 100644 > > > --- a/crypto/aead.c > > > +++ b/crypto/aead.c > > > @@ -35,8 +35,7 @@ static int setkey_unaligned(struct crypto_aead *tfm, const u8 *key, > > > alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1); > > > memcpy(alignbuffer, key, keylen); > > > ret = crypto_aead_alg(tfm)->setkey(tfm, alignbuffer, keylen); > > > - memset(alignbuffer, 0, keylen); > > > - kfree(buffer); > > > + kfree_sensitive(buffer); > > > return ret; > > > } > > > > > > diff --git a/crypto/cipher.c b/crypto/cipher.c > > > index b47141ed4a9f..395f0c2fbb9f 100644 > > > --- a/crypto/cipher.c > > > +++ b/crypto/cipher.c > > > @@ -34,8 +34,7 @@ static int setkey_unaligned(struct crypto_cipher *tfm, const u8 *key, > > > alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1); > > > memcpy(alignbuffer, key, keylen); > > > ret = cia->cia_setkey(crypto_cipher_tfm(tfm), alignbuffer, keylen); > > > - memset(alignbuffer, 0, keylen); > > > - kfree(buffer); > > > + kfree_sensitive(buffer); > > > return ret; > > > > > > Well, the memset()s that you're removing already did the zeroization. This > > patch seems worthwhile as a code simplification, but please don't characterize > > it as a bug fix, because it's not. > > > > > > - Eric > > kfree_sensitive uses memzero_explicit() instead of the memset()s used > above. The memzero_explicit header states - > > * Note: usually using memset() is just fine (!), but in cases > * where clearing out _local_ data at the end of a scope is > * necessary, memzero_explicit() should be used instead in > * order to prevent the compiler from optimising away zeroing. > > It accomplishes this by calling memset() and then adding a barrier. Since > FIPS requires this data be zeroed out, and the current memset() and > kfree() don't guarantee this, I do not think the commit message is > misleading. I can clarify the message with the above information if that > is preferred. > It's heap data, not local data. So no, memzero_explicit() isn't actually needed here. It would convey the intent better, but it's not actually needed. - Eric
