[v3,06/12] ima: Fail rule parsing when the KEY_CHECK hook is combined with an invalid cond
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Message ID 20200709061911.954326-7-tyhicks@linux.microsoft.com
State New
Headers show
Series
  • ima: Fix rule parsing bugs and extend KEXEC_CMDLINE rule support
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Commit Message

Tyler Hicks July 9, 2020, 6:19 a.m. UTC
The KEY_CHECK function only supports the uid, pcr, and keyrings
conditionals. Make this clear at policy load so that IMA policy authors
don't assume that other conditionals are supported.

Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---

* v3
  - Added Lakshmi's Reviewed-by
  - Adjust for the indentation change introduced in patch #4
* v2
  - No change

 security/integrity/ima/ima_policy.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Nayna July 17, 2020, 6:56 p.m. UTC | #1
On 7/9/20 2:19 AM, Tyler Hicks wrote:
> The KEY_CHECK function only supports the uid, pcr, and keyrings
> conditionals. Make this clear at policy load so that IMA policy authors
> don't assume that other conditionals are supported.
>
> Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
> Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> ---
>
> * v3
>    - Added Lakshmi's Reviewed-by
>    - Adjust for the indentation change introduced in patch #4
> * v2
>    - No change
>
>   security/integrity/ima/ima_policy.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 1c64bd6f1728..81da02071d41 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1023,6 +1023,13 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
>   		if (entry->action & ~(MEASURE | DONT_MEASURE))
>   			return false;
>
> +		if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
> +				     IMA_KEYRINGS))
> +			return false;
> +
> +		if (ima_rule_contains_lsm_cond(entry))
> +			return false;
> +
>   		break;
>   	default:
>   		return false;

Should there be a check for IMA_MEASURE_ASYMMETRIC_KEYS in Opt_keyrings 
in ima_parse_rule() to return immediately if not enabled ?

Thanks & Regards,

      - Nayna
Tyler Hicks July 17, 2020, 7:18 p.m. UTC | #2
On 2020-07-17 14:56:46, Nayna wrote:
> 
> On 7/9/20 2:19 AM, Tyler Hicks wrote:
> > The KEY_CHECK function only supports the uid, pcr, and keyrings
> > conditionals. Make this clear at policy load so that IMA policy authors
> > don't assume that other conditionals are supported.
> > 
> > Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
> > Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> > Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> > ---
> > 
> > * v3
> >    - Added Lakshmi's Reviewed-by
> >    - Adjust for the indentation change introduced in patch #4
> > * v2
> >    - No change
> > 
> >   security/integrity/ima/ima_policy.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> > 
> > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> > index 1c64bd6f1728..81da02071d41 100644
> > --- a/security/integrity/ima/ima_policy.c
> > +++ b/security/integrity/ima/ima_policy.c
> > @@ -1023,6 +1023,13 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
> >   		if (entry->action & ~(MEASURE | DONT_MEASURE))
> >   			return false;
> > 
> > +		if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
> > +				     IMA_KEYRINGS))
> > +			return false;
> > +
> > +		if (ima_rule_contains_lsm_cond(entry))
> > +			return false;
> > +
> >   		break;
> >   	default:
> >   		return false;
> 
> Should there be a check for IMA_MEASURE_ASYMMETRIC_KEYS in Opt_keyrings in
> ima_parse_rule() to return immediately if not enabled ?

I didn't notice that "keyrings=" could be disabled at build time. I
think you're right that something like what I have below would be a good idea.

@Lakshmi, do you agree?

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 81da02071d41..bd687560f88e 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1212,6 +1212,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 		case Opt_keyrings:
 			ima_log_string(ab, "keyrings", args[0].from);
 
+			if (!IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS)) {
+				result = -EINVAL;
+				break;
+			}
+
 			keyrings_len = strlen(args[0].from) + 1;
 
 			if ((entry->keyrings) ||

Tyler

> 
> Thanks & Regards,
> 
>      - Nayna
>
Tyler Hicks July 17, 2020, 11:39 p.m. UTC | #3
On 2020-07-17 14:19:03, Tyler Hicks wrote:
> On 2020-07-17 14:56:46, Nayna wrote:
> > 
> > On 7/9/20 2:19 AM, Tyler Hicks wrote:
> > > The KEY_CHECK function only supports the uid, pcr, and keyrings
> > > conditionals. Make this clear at policy load so that IMA policy authors
> > > don't assume that other conditionals are supported.
> > > 
> > > Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys")
> > > Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
> > > Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> > > ---
> > > 
> > > * v3
> > >    - Added Lakshmi's Reviewed-by
> > >    - Adjust for the indentation change introduced in patch #4
> > > * v2
> > >    - No change
> > > 
> > >   security/integrity/ima/ima_policy.c | 7 +++++++
> > >   1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> > > index 1c64bd6f1728..81da02071d41 100644
> > > --- a/security/integrity/ima/ima_policy.c
> > > +++ b/security/integrity/ima/ima_policy.c
> > > @@ -1023,6 +1023,13 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
> > >   		if (entry->action & ~(MEASURE | DONT_MEASURE))
> > >   			return false;
> > > 
> > > +		if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
> > > +				     IMA_KEYRINGS))
> > > +			return false;
> > > +
> > > +		if (ima_rule_contains_lsm_cond(entry))
> > > +			return false;
> > > +
> > >   		break;
> > >   	default:
> > >   		return false;
> > 
> > Should there be a check for IMA_MEASURE_ASYMMETRIC_KEYS in Opt_keyrings in
> > ima_parse_rule() to return immediately if not enabled ?
> 
> I didn't notice that "keyrings=" could be disabled at build time. I
> think you're right that something like what I have below would be a good idea.
> 
> @Lakshmi, do you agree?
> 
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 81da02071d41..bd687560f88e 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -1212,6 +1212,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>  		case Opt_keyrings:
>  			ima_log_string(ab, "keyrings", args[0].from);
>  
> +			if (!IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS)) {
> +				result = -EINVAL;
> +				break;
> +			}
> +
>  			keyrings_len = strlen(args[0].from) + 1;
>  
>  			if ((entry->keyrings) ||
> 

Actually, this change introduces a new compiler warning in another part
of the code that I need to think some more about. I'd like to leave this
patch as-is for now and work on the !CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
case in a separate, later patch when I have some more time to think
about it and test properly.

Tyler

> Tyler
> 
> > 
> > Thanks & Regards,
> > 
> >      - Nayna
> >

Patch
diff mbox series

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 1c64bd6f1728..81da02071d41 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1023,6 +1023,13 @@  static bool ima_validate_rule(struct ima_rule_entry *entry)
 		if (entry->action & ~(MEASURE | DONT_MEASURE))
 			return false;
 
+		if (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR |
+				     IMA_KEYRINGS))
+			return false;
+
+		if (ima_rule_contains_lsm_cond(entry))
+			return false;
+
 		break;
 	default:
 		return false;