[PATCH] Zero some memory after use

[Jeremy Allison]

On Mon, Feb 25, 2019 at 04:35:37PM +0100, Andreas Schneider via samba-technical wrote:
> Hi,
> 
> here are some small patches to zero sensitive memory after use.
> 
> 
> Review much appreciated.

LGTM. RB+ and pushed.

Jeremy.

> 
> 
> 	Andreas
> 
> -- 
> Andreas Schneider                      asn at samba.org
> Samba Team                             www.samba.org
> GPG-ID:     8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D

> From fa613a2ffea9b1d54b6c02a5adbe95dcffaa121b Mon Sep 17 00:00:00 2001
> From: Andreas Schneider <asn at samba.org>
> Date: Thu, 11 Oct 2018 14:33:52 +0200
> Subject: [PATCH 1/3] libcli:smb: Zero sensitive memory after use
> 
> Signed-off-by: Andreas Schneider <asn at samba.org>
> ---
>  libcli/smb/smb2_signing.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/libcli/smb/smb2_signing.c b/libcli/smb/smb2_signing.c
> index 614a2b32dc0..18f5911ad5e 100644
> --- a/libcli/smb/smb2_signing.c
> +++ b/libcli/smb/smb2_signing.c
> @@ -76,6 +76,8 @@ NTSTATUS smb2_signing_sign_pdu(DATA_BLOB signing_key,
>  					vector[i].iov_len);
>  		}
>  		aes_cmac_128_final(&ctx, res);
> +
> +		ZERO_ARRAY(key);
>  	} else {
>  		struct HMACSHA256Context m;
>  		uint8_t digest[SHA256_DIGEST_LENGTH];
> @@ -149,6 +151,8 @@ NTSTATUS smb2_signing_check_pdu(DATA_BLOB signing_key,
>  					vector[i].iov_len);
>  		}
>  		aes_cmac_128_final(&ctx, res);
> +
> +		ZERO_ARRAY(key);
>  	} else {
>  		struct HMACSHA256Context m;
>  		uint8_t digest[SHA256_DIGEST_LENGTH];
> -- 
> 2.20.1
> 
> 
> From c5a3fc943283b579e2cb5cf415e4dca689e8a149 Mon Sep 17 00:00:00 2001
> From: Andreas Schneider <asn at samba.org>
> Date: Tue, 30 Oct 2018 17:08:35 +0100
> Subject: [PATCH 2/3] auth:gensec: Make sure we zero the checksum after use
> 
> Signed-off-by: Andreas Schneider <asn at samba.org>
> ---
>  auth/gensec/schannel.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/auth/gensec/schannel.c b/auth/gensec/schannel.c
> index 364a0fcc186..441801bac47 100644
> --- a/auth/gensec/schannel.c
> +++ b/auth/gensec/schannel.c
> @@ -347,6 +347,8 @@ static NTSTATUS netsec_incoming_packet(struct schannel_state *state,
>  
>  	netsec_do_seq_num(state, checksum, checksum_length, seq_num);
>  
> +	ZERO_ARRAY(checksum);
> +
>  	ret = memcmp(seq_num, sig->data+8, 8);
>  	if (ret != 0) {
>  		dump_data_pw("calc seq num:", seq_num, 8);
> -- 
> 2.20.1
> 
> 
> From 832d68eca476709f34ce1275babf729eec23fd5b Mon Sep 17 00:00:00 2001
> From: Andreas Schneider <asn at samba.org>
> Date: Fri, 26 Oct 2018 14:50:29 +0200
> Subject: [PATCH 3/3] libcli:auth: Avoid explicit ZERO_STRUCT
> 
> Signed-off-by: Andreas Schneider <asn at samba.org>
> ---
>  libcli/auth/credentials.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/libcli/auth/credentials.c b/libcli/auth/credentials.c
> index b6c8ba281ba..fcd5e34cc9b 100644
> --- a/libcli/auth/credentials.c
> +++ b/libcli/auth/credentials.c
> @@ -76,14 +76,12 @@ static void netlogon_creds_init_128bit(struct netlogon_creds_CredentialState *cr
>  				       const struct netr_Credential *server_challenge,
>  				       const struct samr_Password *machine_password)
>  {
> -	unsigned char zero[4], tmp[16];
> +	uint8_t zero[4] = {0}, tmp[16];
>  	HMACMD5Context ctx;
>  	MD5_CTX md5;
>  
>  	ZERO_ARRAY(creds->session_key);
>  
> -	memset(zero, 0, sizeof(zero));
> -
>  	hmac_md5_init_rfc2104(machine_password->hash, sizeof(machine_password->hash), &ctx);
>  	MD5Init(&md5);
>  	MD5Update(&md5, zero, sizeof(zero));
> -- 
> 2.20.1
>