Re: [PATCH ipsec-next] xfrm: add /proc/sys/core/net/xfrm_redact_secret

[Stephan Mueller <smueller@chronox.de>]

Am Dienstag, 28. Juli 2020, 17:47:30 CEST schrieb Antony Antony:

Hi Antony,

> when enabled, 1, redact XFRM SA secret in the netlink response to
> xfrm_get_sa() or dump all sa.
> 
> e.g
> echo 1 > /proc/sys/net/core/xfrm_redact_secret
> ip xfrm state
> src 172.16.1.200 dst 172.16.1.100
> 	proto esp spi 0x00000002 reqid 2 mode tunnel
> 	replay-window 0
> 	aead rfc4106(gcm(aes)) 0x0000000000000000000000000000000000000000 96
> 
> the aead secret is redacted.
> 
> /proc/sys/core/net/xfrm_redact_secret is a toggle.
> Once enabled, either at compile or via proc, it can not be disabled.
> Redacting secret is a FIPS 140-2 requirement.
> 
> Cc: Stephan Mueller <smueller@chronox.de>
> Signed-off-by: Antony Antony <antony.antony@secunet.com>
> ---
>  Documentation/networking/xfrm_sysctl.rst |  7 +++
>  include/net/netns/xfrm.h                 |  1 +
>  net/xfrm/Kconfig                         | 10 ++++
>  net/xfrm/xfrm_sysctl.c                   | 20 +++++++
>  net/xfrm/xfrm_user.c                     | 76 +++++++++++++++++++++---
>  5 files changed, 105 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/networking/xfrm_sysctl.rst
> b/Documentation/networking/xfrm_sysctl.rst index 47b9bbdd0179..26432b0ff3ac
> 100644
> --- a/Documentation/networking/xfrm_sysctl.rst
> +++ b/Documentation/networking/xfrm_sysctl.rst
> @@ -9,3 +9,10 @@ XFRM Syscall
> 
>  xfrm_acq_expires - INTEGER
>  	default 30 - hard timeout in seconds for acquire requests
> +
> +xfrm_redact_secret - INTEGER
> +	A toggle to redact xfrm SA's secret to userspace.
> +	When true the kernel, netlink message will redact SA secret
> +	to userspace. This is part of FIPS 140-2 requirement.
> +	Once the value is set to true, either at compile or at run time,
> +	it can not be set to false.
> diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
> index 59f45b1e9dac..0ca9328daad4 100644
> --- a/include/net/netns/xfrm.h
> +++ b/include/net/netns/xfrm.h
> @@ -64,6 +64,7 @@ struct netns_xfrm {
>  	u32			sysctl_aevent_rseqth;
>  	int			sysctl_larval_drop;
>  	u32			sysctl_acq_expires;
> +	u32			sysctl_redact_secret;
>  #ifdef CONFIG_SYSCTL
>  	struct ctl_table_header	*sysctl_hdr;
>  #endif
> diff --git a/net/xfrm/Kconfig b/net/xfrm/Kconfig
> index 5b9a5ab48111..270a4e906a15 100644
> --- a/net/xfrm/Kconfig
> +++ b/net/xfrm/Kconfig
> @@ -91,6 +91,16 @@ config XFRM_ESP
>  	select CRYPTO_SEQIV
>  	select CRYPTO_SHA256
> 
> +config XFRM_REDACT_SECRET
> +	bool "Redact xfrm SA secret in netlink message"
> +	depends on SYSCTL
> +	default n
> +	help
> +	  Enable XFRM SA secret redact in the netlink message.
> +	  Redacting secret is a FIPS 140-2 requirement.
> +	  Once enabled at compile, the value can not be set to false on
> +	  a running system.
> +
>  config XFRM_IPCOMP
>  	tristate
>  	select XFRM_ALGO
> diff --git a/net/xfrm/xfrm_sysctl.c b/net/xfrm/xfrm_sysctl.c
> index 0c6c5ef65f9d..a41aa325a478 100644
> --- a/net/xfrm/xfrm_sysctl.c
> +++ b/net/xfrm/xfrm_sysctl.c
> @@ -4,15 +4,25 @@
>  #include <net/net_namespace.h>
>  #include <net/xfrm.h>
> 
> +#ifdef CONFIG_SYSCTL
> +#ifdef CONFIG_XFRM_REDACT_SECRET
> +#define XFRM_REDACT_SECRET  1
> +#else
> +#define XFRM_REDACT_SECRET  0
> +#endif
> +#endif
> +
>  static void __net_init __xfrm_sysctl_init(struct net *net)
>  {
>  	net->xfrm.sysctl_aevent_etime = XFRM_AE_ETIME;
>  	net->xfrm.sysctl_aevent_rseqth = XFRM_AE_SEQT_SIZE;
>  	net->xfrm.sysctl_larval_drop = 1;
>  	net->xfrm.sysctl_acq_expires = 30;
> +	net->xfrm.sysctl_redact_secret = XFRM_REDACT_SECRET;
>  }
> 
>  #ifdef CONFIG_SYSCTL
> +
>  static struct ctl_table xfrm_table[] = {
>  	{
>  		.procname	= "xfrm_aevent_etime",
> @@ -38,6 +48,15 @@ static struct ctl_table xfrm_table[] = {
>  		.mode		= 0644,
>  		.proc_handler	= proc_dointvec
>  	},
> +	{
> +		.procname	= "xfrm_redact_secret",
> +		.maxlen		= sizeof(u32),
> +		.mode		= 0644,
> +		/* only handle a transition from "0" to "1" */
> +		.proc_handler	= proc_dointvec_minmax,
> +		.extra1         = SYSCTL_ONE,
> +		.extra2         = SYSCTL_ONE,
> +	},
>  	{}
>  };
> 
> @@ -54,6 +73,7 @@ int __net_init xfrm_sysctl_init(struct net *net)
>  	table[1].data = &net->xfrm.sysctl_aevent_rseqth;
>  	table[2].data = &net->xfrm.sysctl_larval_drop;
>  	table[3].data = &net->xfrm.sysctl_acq_expires;
> +	table[4].data = &net->xfrm.sysctl_redact_secret;
> 
>  	/* Don't export sysctls to unprivileged users */
>  	if (net->user_ns != &init_user_ns)
> diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
> index e6cfaa680ef3..a3e89dddea9d 100644
> --- a/net/xfrm/xfrm_user.c
> +++ b/net/xfrm/xfrm_user.c
> @@ -848,21 +848,78 @@ static int copy_user_offload(struct xfrm_state_offload
> *xso, struct sk_buff *skb return 0;
>  }
> 
> -static int copy_to_user_auth(struct xfrm_algo_auth *auth, struct sk_buff
> *skb) +static int copy_to_user_auth(u32 redact_secret, struct
> xfrm_algo_auth *auth, +			     struct sk_buff *skb)
>  {
>  	struct xfrm_algo *algo;
> +	struct xfrm_algo_auth *ap;
>  	struct nlattr *nla;
> 
>  	nla = nla_reserve(skb, XFRMA_ALG_AUTH,
>  			  sizeof(*algo) + (auth->alg_key_len + 7) / 8);
>  	if (!nla)
>  		return -EMSGSIZE;
> -
>  	algo = nla_data(nla);
>  	strncpy(algo->alg_name, auth->alg_name, sizeof(algo->alg_name));
> -	memcpy(algo->alg_key, auth->alg_key, (auth->alg_key_len + 7) / 8);
> +
> +	if (redact_secret && auth->alg_key_len)
> +		memset(algo->alg_key, 0, (auth->alg_key_len + 7) / 8);
> +	else
> +		memcpy(algo->alg_key, auth->alg_key,
> +		       (auth->alg_key_len + 7) / 8);
>  	algo->alg_key_len = auth->alg_key_len;
> 
> +	nla = nla_reserve(skb, XFRMA_ALG_AUTH_TRUNC, xfrm_alg_auth_len(auth));
> +	if (!nla)
> +		return -EMSGSIZE;
> +	ap = nla_data(nla);
> +	memcpy(ap, auth, sizeof(struct xfrm_algo_auth));
> +	if (redact_secret)

You test for auth->alg_key_len above. Shouldn't there such a check here too?

> +		memset(ap->alg_key, 0, (auth->alg_key_len + 7) / 8);
> +	else
> +		memcpy(ap->alg_key, auth->alg_key,
> +		       (auth->alg_key_len + 7) / 8);
> +	return 0;
> +}
> +
> +static int copy_to_user_aead(u32 redact_secret,
> +			     struct xfrm_algo_aead *aead, struct sk_buff *skb)
> +{
> +	struct nlattr *nla = nla_reserve(skb, XFRMA_ALG_AEAD, aead_len(aead));
> +	struct xfrm_algo_aead *ap;
> +
> +	if (!nla)
> +		return -EMSGSIZE;
> +
> +	ap = nla_data(nla);
> +	memcpy(ap, aead, sizeof(*aead));
> +
> +	if (redact_secret)

And here?

> +		memset(ap->alg_key, 0, (aead->alg_key_len + 7) / 8);
> +	else
> +		memcpy(ap->alg_key, aead->alg_key,
> +		       (aead->alg_key_len + 7) / 8);
> +	return 0;
> +}
> +
> +static int copy_to_user_ealg(u32 redact_secret, struct xfrm_algo *ealg,
> +			     struct sk_buff *skb)
> +{
> +	struct xfrm_algo *ap;
> +	struct nlattr *nla = nla_reserve(skb, XFRMA_ALG_CRYPT,
> +					 xfrm_alg_len(ealg));
> +	if (!nla)
> +		return -EMSGSIZE;
> +
> +	ap = nla_data(nla);
> +	memcpy(ap, ealg, sizeof(*ealg));
> +
> +	if (redact_secret)

Here, too?

> +		memset(ap->alg_key, 0, (ealg->alg_key_len + 7) / 8);
> +	else
> +		memcpy(ap->alg_key, ealg->alg_key,
> +		       (ealg->alg_key_len + 7) / 8);
> +
>  	return 0;
>  }
> 
> @@ -884,6 +941,7 @@ static int copy_to_user_state_extra(struct xfrm_state
> *x, struct sk_buff *skb)
>  {
>  	int ret = 0;
> +	struct net *net = xs_net(x);
> 
>  	copy_to_user_state(x, p);
> 
> @@ -906,20 +964,20 @@ static int copy_to_user_state_extra(struct xfrm_state
> *x, goto out;
>  	}
>  	if (x->aead) {
> -		ret = nla_put(skb, XFRMA_ALG_AEAD, aead_len(x->aead), x-
>aead);
> +		ret = copy_to_user_aead(net->xfrm.sysctl_redact_secret,
> +					x->aead, skb);
>  		if (ret)
>  			goto out;
>  	}
>  	if (x->aalg) {
> -		ret = copy_to_user_auth(x->aalg, skb);
> -		if (!ret)
> -			ret = nla_put(skb, XFRMA_ALG_AUTH_TRUNC,
> -				      xfrm_alg_auth_len(x->aalg), x->aalg);
> +		ret = copy_to_user_auth(net->xfrm.sysctl_redact_secret,
> +					x->aalg, skb);
>  		if (ret)
>  			goto out;
>  	}
>  	if (x->ealg) {
> -		ret = nla_put(skb, XFRMA_ALG_CRYPT, xfrm_alg_len(x->ealg), x-
>ealg);
> +		ret = copy_to_user_ealg(net->xfrm.sysctl_redact_secret,
> +					x->ealg, skb);
>  		if (ret)
>  			goto out;
>  	}


Ciao
Stephan