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parser: fix abi rule and pinned feature file interaction

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In AppArmor 2 distros could pin the feature file being used by setting
the feature-file option in the config file.

With AppArmor 3 policy is now explicitly tagged with an abi rule.

The problem is the interaction on systems that have a mixture of
AppArmor 2 and AppArmor 3 policy and use feature pinning.

The feature pinning is required to make the apparmor 2 policy behave
as expected but it also overrides the abi rules that are explicitly
set as part of the policy. This means we either have the apparmor 2
pinned policy working as desired or the apparmor 3 policy, but not
both.

To fix this make setting the flag on command line or in config file
lower priority than an abi rule specified in policy. The ability
to override abi rules will be added in a separate patch.

The Priority ordering to determine the policy abi to use is
1. Use abi rules if present
2. if no abi rule use command line option
3. if no abi rule or command line option use config setting
4. if none of the above use the default abi

PR: https://gitlab.com/apparmor/apparmor/-/merge_requests/579
Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
John Johansen 2020-07-09 02:43:10 -07:00
parent 2f5d5e1b24
commit acb45dc4b0
4 changed files with 41 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
parser/apparmor.d.pod
View File

@ -1727,6 +1727,17 @@ If the policy abi is specified as B<kernel> then the running kernel's
abi will be used. This should never be used in shipped policy as it
can cause system breakage when a new kernel is installed.
=head3 ABI compatability with AppArmor 2.x
AppArmor 3 remains compatible with AppArmor 2.x by detecting when a
profile does not have a feature ABI specified. In this case the policy
compile will either apply the pinned feature ABI as specified by the
config file or the command line, or if neither of those are applied by
using a default feature ABI.
It is important to note that the default feature ABI does not support
new features added in AppArmor 3 or later.
=head1 EXAMPLE
An example AppArmor profile:

1
parser/parser.h
View File

@ -295,6 +295,7 @@ extern uint32_t policy_version;
extern uint32_t parser_abi_version;
extern uint32_t kernel_abi_version;
extern aa_features *pinned_features;
extern aa_features *policy_features;
extern aa_features *kernel_features;

41
parser/parser_main.c
View File

@ -109,8 +109,8 @@ static const char *cacheloc[MAX_CACHE_LOCS];
static int cacheloc_n = 0;
static bool print_cache_dir = false;
aa_features *pinned_features = NULL;
aa_features *policy_features = NULL;
bool specified_policy_features = false;
aa_features *kernel_features = NULL;
static const char *config_file = "/etc/apparmor/parser.conf";
@ -407,6 +407,7 @@ bool early_arg(int c) {
*/
static int process_arg(int c, char *optarg)
{
struct aa_features *tmp_features = NULL;
int count = 0;
switch (c) {
@ -529,32 +530,32 @@ static int process_arg(int c, char *optarg)
}
break;
case 'm':
if (policy_features)
aa_features_unref(policy_features);
if (pinned_features)
aa_features_unref(pinned_features);
if (kernel_features)
aa_features_unref(kernel_features);
if (aa_features_new_from_string(&policy_features,
if (aa_features_new_from_string(&tmp_features,
optarg, strlen(optarg))) {
fprintf(stderr,
"Failed to parse features string: %m\n");
exit(1);
}
kernel_features = aa_features_ref(policy_features);
specified_policy_features = true;
kernel_features = aa_features_ref(tmp_features);
pinned_features = tmp_features;
break;
case 'M':
if (policy_features)
aa_features_unref(policy_features);
if (pinned_features)
aa_features_unref(pinned_features);
if (kernel_features)
aa_features_unref(kernel_features);
if (aa_features_new(&policy_features, AT_FDCWD, optarg)) {
if (aa_features_new(&tmp_features, AT_FDCWD, optarg)) {
fprintf(stderr,
"Failed to load features from '%s': %m\n",
optarg);
exit(1);
}
kernel_features = aa_features_ref(policy_features);
specified_policy_features = true;
kernel_features = aa_features_ref(tmp_features);
pinned_features = tmp_features;
break;
case 138:
if (kernel_features)
@ -567,21 +568,21 @@ static int process_arg(int c, char *optarg)
}
break;
case 139:
if (policy_features)
aa_features_unref(policy_features);
if (pinned_features)
aa_features_unref(pinned_features);
if (strcmp(optarg, "<kernel>") == 0) {
if (aa_features_new_from_kernel(&policy_features)) {
if (aa_features_new_from_kernel(&tmp_features)) {
fprintf(stderr,
"Failed to load kernel features into the policy-features abi: %m\n");
exit(1);
}
} else if (aa_features_new(&policy_features, AT_FDCWD, optarg)) {
} else if (aa_features_new(&tmp_features, AT_FDCWD, optarg)) {
fprintf(stderr,
"Failed to load policy-features from '%s': %m\n",
optarg);
exit(1);
}
specified_policy_features = true;
pinned_features = tmp_features;
break;
case 'q':
conf_verbose = 0;
@ -920,11 +921,9 @@ void reset_parser(const char *filename)
free_symtabs();
free_policies();
reset_include_stack(filename);
if (!specified_policy_features) {
aa_features_unref(policy_features);
policy_features = NULL;
clear_cap_flag(CAPFLAG_POLICY_FEATURE);
}
aa_features_unref(policy_features);
policy_features = NULL;
clear_cap_flag(CAPFLAG_POLICY_FEATURE);
}
int test_for_dir_mode(const char *basename, const char *linkdir)

14
parser/parser_yacc.y
View File

@ -292,13 +292,17 @@ list: preamble
{
/* make sure abi is setup */
if (policy_features == NULL) {
if (pinned_features) {
policy_features = aa_features_ref(pinned_features);
/* use default feature abi */
if (aa_features_new_from_string(&policy_features,
default_features_abi,
strlen(default_features_abi))) {
yyerror(_("Failed to setup default policy feature abi"));
} else {
if (aa_features_new_from_string(&policy_features,
default_features_abi,
strlen(default_features_abi))) {
yyerror(_("Failed to setup default policy feature abi"));
}
pwarn(_("%s: File '%s' missing feature abi, falling back to default policy feature abi\n"), progname, current_filename);
}
pwarn(_("%s: File '%s' missing feature abi, falling back to default policy feature abi\n"), progname, current_filename);
}
if (!add_cap_feature_mask(policy_features,
CAPFLAG_POLICY_FEATURE))