2024-04-15 22:19:32

by Mothershead, Hailey

Subject: [PATCH v2 2/2] crypto: aead,cipher - zeroize key buffer after use

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 <[email protected]>
---
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;

}
--
2.40.1

memsets removed and first patch in series dropped.

2024-04-15 22:49:52

by Eric Biggers

Subject: Re: [PATCH v2 2/2] crypto: aead,cipher - zeroize key buffer after use

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 <[email protected]>
> ---
> 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