Re: [PATCH v2 09/11] ima: Move validation of the keyrings conditional into ima_validate_rule()

[Lakshmi Ramasubramanian]

On 6/26/20 3:38 PM, Tyler Hicks wrote:

Use ima_validate_rule() to ensure that the combination of a hook
function and the keyrings conditional is valid and that the keyrings
conditional is not specified without an explicit KEY_CHECK func
conditional. This is a code cleanup and has no user-facing change.

In addition to checking for func=KEY_CHECK and the keyrings conditional, 
the patch also validates the flags for other IMA hooks (such as 
KEXEC_KERNEL_CHECK, POLICY_CHECK, etc.) Would be good to mention that in 
the patch description.

 -lakshmi


Signed-off-by: Tyler Hicks <tyhi...@linux.microsoft.com>
---

* v2
   - Allowed IMA_DIGSIG_REQUIRED, IMA_PERMIT_DIRECTIO,
     IMA_MODSIG_ALLOWED, and IMA_CHECK_BLACKLIST conditionals to be
     present in the rule entry flags for non-buffer hook functions.

  security/integrity/ima/ima_policy.c | 13 +++++++++++--
  1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c 
b/security/integrity/ima/ima_policy.c
index 8cdca2399d59..43d49ad958fb 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1000,6 +1000,15 @@ static bool ima_validate_rule(struct ima_rule_entry 
*entry)
                case KEXEC_KERNEL_CHECK:
                case KEXEC_INITRAMFS_CHECK:
                case POLICY_CHECK:
+                       if (entry->flags & ~(IMA_FUNC | IMA_MASK | IMA_FSMAGIC |
+                                            IMA_UID | IMA_FOWNER | IMA_FSUUID |
+                                            IMA_INMASK | IMA_EUID | IMA_PCR |
+                                            IMA_FSNAME | IMA_DIGSIG_REQUIRED |
+                                            IMA_PERMIT_DIRECTIO |
+                                            IMA_MODSIG_ALLOWED |
+                                            IMA_CHECK_BLACKLIST))
+                               return false;
+
                        break;
                case KEXEC_CMDLINE:
                        if (entry->action & ~(MEASURE | DONT_MEASURE))
@@ -1027,7 +1036,8 @@ static bool ima_validate_rule(struct ima_rule_entry 
*entry)
                default:
                        return false;
                }
-       }
+       } else if (entry->flags & IMA_KEYRINGS)
+               return false;
  
  	return true;
  }
@@ -1209,7 +1219,6 @@ static int ima_parse_rule(char *rule, struct 
ima_rule_entry *entry)
                        keyrings_len = strlen(args[0].from) + 1;
  
  			if ((entry->keyrings) ||
-                           (entry->func != KEY_CHECK) ||
                            (keyrings_len < 2)) {
                                result = -EINVAL;
                                break;