[RFC,v7,21/41] richacl: Move everyone@ aces down the acl
diff mbox

Message ID 1441448856-13478-22-git-send-email-agruenba@redhat.com
State New
Headers show

Commit Message

Andreas Gruenbacher Sept. 5, 2015, 10:27 a.m. UTC
The POSIX standard puts processes which are not the owner or a member in
the owning group or which match any ace other then everyone@ on the
other file class.  We only know if a process is in the other class after
processing the entire acl.

Move all everyone@ aces in the acl down in the acl so that at most a
single everyone@ allow ace remains at the end.  Permissions which are
not explicitly allowed are implicitly denied, so an everyone@ deny ace
is unneeded.

The everyone@ aces can be moved down the acl without changing the
permissions that the acl grants.  This transformation simplifies the
following algorithms, and eventually allows us to turn the final
everyone@ allow ace into an entry for the other class.

Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
---
 fs/richacl_compat.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

Comments

J . Bruce Fields Sept. 18, 2015, 7:35 p.m. UTC | #1
On Sat, Sep 05, 2015 at 12:27:16PM +0200, Andreas Gruenbacher wrote:
> The POSIX standard puts processes which are not the owner or a member in
> the owning group or which match any ace other then everyone@ on the
> other file class.  We only know if a process is in the other class after
> processing the entire acl.
> 
> Move all everyone@ aces in the acl down in the acl so that at most a
> single everyone@ allow ace remains at the end.  Permissions which are
> not explicitly allowed are implicitly denied, so an everyone@ deny ace
> is unneeded.
> 
> The everyone@ aces can be moved down the acl without changing the
> permissions that the acl grants.  This transformation simplifies the
> following algorithms, and eventually allows us to turn the final
> everyone@ allow ace into an entry for the other class.
> 
> Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
> ---
>  fs/richacl_compat.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
> index 341e429..4f0acf5 100644
> --- a/fs/richacl_compat.c
> +++ b/fs/richacl_compat.c
> @@ -153,3 +153,68 @@ richace_change_mask(struct richacl_alloc *alloc, struct richace **ace,
>  	}
>  	return 0;
>  }
> +
> +/**
> + * richacl_move_everyone_aces_down  -  move everyone@ aces to the end of the acl
> + * @alloc:	acl and number of allocated entries
> + *
> + * Move all everyone aces to the end of the acl so that only a single everyone@
> + * allow ace remains at the end, and update the mask fields of all aces on the
> + * way.  The last ace of the resulting acl will be an everyone@ allow ace only
> + * if @acl grants any permissions to @everyone.  No @everyone deny aces will
> + * remain.
> + *
> + * This transformation does not alter the permissions that the acl grants.
> + * Having at most one everyone@ allow ace at the end of the acl helps us in the
> + * following algorithms.
> + */
> +static int
> +richacl_move_everyone_aces_down(struct richacl_alloc *alloc)
> +{
> +	struct richace *ace;
> +	unsigned int allowed = 0, denied = 0;
> +
> +	richacl_for_each_entry(ace, alloc->acl) {
> +		if (richace_is_inherit_only(ace))
> +			continue;
> +		if (richace_is_everyone(ace)) {
> +			if (richace_is_allow(ace))
> +				allowed |= (ace->e_mask & ~denied);
> +			else if (richace_is_deny(ace))
> +				denied |= (ace->e_mask & ~allowed);
> +			else
> +				continue;
> +			if (richace_change_mask(alloc, &ace, 0))
> +				return -1;
> +		} else {
> +			if (richace_is_allow(ace)) {
> +				if (richace_change_mask(alloc, &ace, allowed |
> +						(ace->e_mask & ~denied)))
> +					return -1;
> +			} else if (richace_is_deny(ace)) {
> +				if (richace_change_mask(alloc, &ace, denied |
> +						(ace->e_mask & ~allowed)))
> +					return -1;
> +			}
> +		}
> +	}
> +	if (allowed & ~RICHACE_POSIX_ALWAYS_ALLOWED) {
> +		struct richace *last_ace = ace - 1;
> +
> +		if (alloc->acl->a_entries &&
> +		    richace_is_everyone(last_ace) &&
> +		    richace_is_allow(last_ace) &&
> +		    richace_is_inherit_only(last_ace) &&
> +		    last_ace->e_mask == allowed)
> +			last_ace->e_flags &= ~RICHACE_INHERIT_ONLY_ACE;

That's a funny special case!  Is it even worth it, or could we just live
with an extra uninheritable EVERYONE ace in this case?

Anyway, again I like the way you've set this all up with the little
acl-editing helpers, it makes this easier to follow than it otherwise
would be....

	Reviewed-by: J. Bruce Fields <bfields@redhat.com>

--b.

> +		else {
> +			if (richacl_insert_entry(alloc, &ace))
> +				return -1;
> +			ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
> +			ace->e_flags = RICHACE_SPECIAL_WHO;
> +			ace->e_mask = allowed;
> +			ace->e_id.special = RICHACE_EVERYONE_SPECIAL_ID;
> +		}
> +	}
> +	return 0;
> +}
> -- 
> 2.4.3
> 
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Andreas Gruenbacher Sept. 21, 2015, 9:43 p.m. UTC | #2
2015-09-18 21:35 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>:
> On Sat, Sep 05, 2015 at 12:27:16PM +0200, Andreas Gruenbacher wrote:
>> The POSIX standard puts processes which are not the owner or a member in
>> the owning group or which match any ace other then everyone@ on the
>> other file class.  We only know if a process is in the other class after
>> processing the entire acl.
>>
>> Move all everyone@ aces in the acl down in the acl so that at most a
>> single everyone@ allow ace remains at the end.  Permissions which are
>> not explicitly allowed are implicitly denied, so an everyone@ deny ace
>> is unneeded.
>>
>> The everyone@ aces can be moved down the acl without changing the
>> permissions that the acl grants.  This transformation simplifies the
>> following algorithms, and eventually allows us to turn the final
>> everyone@ allow ace into an entry for the other class.
>>
>> Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
>> ---
>>  fs/richacl_compat.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 65 insertions(+)
>>
>> diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
>> index 341e429..4f0acf5 100644
>> --- a/fs/richacl_compat.c
>> +++ b/fs/richacl_compat.c
>> @@ -153,3 +153,68 @@ richace_change_mask(struct richacl_alloc *alloc, struct richace **ace,
>>       }
>>       return 0;
>>  }
>> +
>> +/**
>> + * richacl_move_everyone_aces_down  -  move everyone@ aces to the end of the acl
>> + * @alloc:   acl and number of allocated entries
>> + *
>> + * Move all everyone aces to the end of the acl so that only a single everyone@
>> + * allow ace remains at the end, and update the mask fields of all aces on the
>> + * way.  The last ace of the resulting acl will be an everyone@ allow ace only
>> + * if @acl grants any permissions to @everyone.  No @everyone deny aces will
>> + * remain.
>> + *
>> + * This transformation does not alter the permissions that the acl grants.
>> + * Having at most one everyone@ allow ace at the end of the acl helps us in the
>> + * following algorithms.
>> + */
>> +static int
>> +richacl_move_everyone_aces_down(struct richacl_alloc *alloc)
>> +{
>> +     struct richace *ace;
>> +     unsigned int allowed = 0, denied = 0;
>> +
>> +     richacl_for_each_entry(ace, alloc->acl) {
>> +             if (richace_is_inherit_only(ace))
>> +                     continue;
>> +             if (richace_is_everyone(ace)) {
>> +                     if (richace_is_allow(ace))
>> +                             allowed |= (ace->e_mask & ~denied);
>> +                     else if (richace_is_deny(ace))
>> +                             denied |= (ace->e_mask & ~allowed);
>> +                     else
>> +                             continue;
>> +                     if (richace_change_mask(alloc, &ace, 0))
>> +                             return -1;
>> +             } else {
>> +                     if (richace_is_allow(ace)) {
>> +                             if (richace_change_mask(alloc, &ace, allowed |
>> +                                             (ace->e_mask & ~denied)))
>> +                                     return -1;
>> +                     } else if (richace_is_deny(ace)) {
>> +                             if (richace_change_mask(alloc, &ace, denied |
>> +                                             (ace->e_mask & ~allowed)))
>> +                                     return -1;
>> +                     }
>> +             }
>> +     }
>> +     if (allowed & ~RICHACE_POSIX_ALWAYS_ALLOWED) {
>> +             struct richace *last_ace = ace - 1;
>> +
>> +             if (alloc->acl->a_entries &&
>> +                 richace_is_everyone(last_ace) &&
>> +                 richace_is_allow(last_ace) &&
>> +                 richace_is_inherit_only(last_ace) &&
>> +                 last_ace->e_mask == allowed)
>> +                     last_ace->e_flags &= ~RICHACE_INHERIT_ONLY_ACE;
>
> That's a funny special case!  Is it even worth it, or could we just live
> with an extra uninheritable EVERYONE ace in this case?

Inheritable everyone@ allow entries at the end of the ACL are not
uncommon. This special case prevents the algorithm from splitting such
entries into inherit-only and non-inheritable parts.

> Anyway, again I like the way you've set this all up with the little
> acl-editing helpers, it makes this easier to follow than it otherwise
> would be....

Great to hear that :)

Thanks,
Andreas
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J . Bruce Fields Sept. 22, 2015, 1:52 a.m. UTC | #3
On Mon, Sep 21, 2015 at 11:43:16PM +0200, Andreas Gruenbacher wrote:
> 2015-09-18 21:35 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>:
> > On Sat, Sep 05, 2015 at 12:27:16PM +0200, Andreas Gruenbacher wrote:
> >> The POSIX standard puts processes which are not the owner or a member in
> >> the owning group or which match any ace other then everyone@ on the
> >> other file class.  We only know if a process is in the other class after
> >> processing the entire acl.
> >>
> >> Move all everyone@ aces in the acl down in the acl so that at most a
> >> single everyone@ allow ace remains at the end.  Permissions which are
> >> not explicitly allowed are implicitly denied, so an everyone@ deny ace
> >> is unneeded.
> >>
> >> The everyone@ aces can be moved down the acl without changing the
> >> permissions that the acl grants.  This transformation simplifies the
> >> following algorithms, and eventually allows us to turn the final
> >> everyone@ allow ace into an entry for the other class.
> >>
> >> Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
> >> ---
> >>  fs/richacl_compat.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 65 insertions(+)
> >>
> >> diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
> >> index 341e429..4f0acf5 100644
> >> --- a/fs/richacl_compat.c
> >> +++ b/fs/richacl_compat.c
> >> @@ -153,3 +153,68 @@ richace_change_mask(struct richacl_alloc *alloc, struct richace **ace,
> >>       }
> >>       return 0;
> >>  }
> >> +
> >> +/**
> >> + * richacl_move_everyone_aces_down  -  move everyone@ aces to the end of the acl
> >> + * @alloc:   acl and number of allocated entries
> >> + *
> >> + * Move all everyone aces to the end of the acl so that only a single everyone@
> >> + * allow ace remains at the end, and update the mask fields of all aces on the
> >> + * way.  The last ace of the resulting acl will be an everyone@ allow ace only
> >> + * if @acl grants any permissions to @everyone.  No @everyone deny aces will
> >> + * remain.
> >> + *
> >> + * This transformation does not alter the permissions that the acl grants.
> >> + * Having at most one everyone@ allow ace at the end of the acl helps us in the
> >> + * following algorithms.
> >> + */
> >> +static int
> >> +richacl_move_everyone_aces_down(struct richacl_alloc *alloc)
> >> +{
> >> +     struct richace *ace;
> >> +     unsigned int allowed = 0, denied = 0;
> >> +
> >> +     richacl_for_each_entry(ace, alloc->acl) {
> >> +             if (richace_is_inherit_only(ace))
> >> +                     continue;
> >> +             if (richace_is_everyone(ace)) {
> >> +                     if (richace_is_allow(ace))
> >> +                             allowed |= (ace->e_mask & ~denied);
> >> +                     else if (richace_is_deny(ace))
> >> +                             denied |= (ace->e_mask & ~allowed);
> >> +                     else
> >> +                             continue;
> >> +                     if (richace_change_mask(alloc, &ace, 0))
> >> +                             return -1;
> >> +             } else {
> >> +                     if (richace_is_allow(ace)) {
> >> +                             if (richace_change_mask(alloc, &ace, allowed |
> >> +                                             (ace->e_mask & ~denied)))
> >> +                                     return -1;
> >> +                     } else if (richace_is_deny(ace)) {
> >> +                             if (richace_change_mask(alloc, &ace, denied |
> >> +                                             (ace->e_mask & ~allowed)))
> >> +                                     return -1;
> >> +                     }
> >> +             }
> >> +     }
> >> +     if (allowed & ~RICHACE_POSIX_ALWAYS_ALLOWED) {
> >> +             struct richace *last_ace = ace - 1;
> >> +
> >> +             if (alloc->acl->a_entries &&
> >> +                 richace_is_everyone(last_ace) &&
> >> +                 richace_is_allow(last_ace) &&
> >> +                 richace_is_inherit_only(last_ace) &&
> >> +                 last_ace->e_mask == allowed)
> >> +                     last_ace->e_flags &= ~RICHACE_INHERIT_ONLY_ACE;
> >
> > That's a funny special case!  Is it even worth it, or could we just live
> > with an extra uninheritable EVERYONE ace in this case?
> 
> Inheritable everyone@ allow entries at the end of the ACL are not
> uncommon. This special case prevents the algorithm from splitting such
> entries into inherit-only and non-inheritable parts.

OK.--b.
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Patch
diff mbox

diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
index 341e429..4f0acf5 100644
--- a/fs/richacl_compat.c
+++ b/fs/richacl_compat.c
@@ -153,3 +153,68 @@  richace_change_mask(struct richacl_alloc *alloc, struct richace **ace,
 	}
 	return 0;
 }
+
+/**
+ * richacl_move_everyone_aces_down  -  move everyone@ aces to the end of the acl
+ * @alloc:	acl and number of allocated entries
+ *
+ * Move all everyone aces to the end of the acl so that only a single everyone@
+ * allow ace remains at the end, and update the mask fields of all aces on the
+ * way.  The last ace of the resulting acl will be an everyone@ allow ace only
+ * if @acl grants any permissions to @everyone.  No @everyone deny aces will
+ * remain.
+ *
+ * This transformation does not alter the permissions that the acl grants.
+ * Having at most one everyone@ allow ace at the end of the acl helps us in the
+ * following algorithms.
+ */
+static int
+richacl_move_everyone_aces_down(struct richacl_alloc *alloc)
+{
+	struct richace *ace;
+	unsigned int allowed = 0, denied = 0;
+
+	richacl_for_each_entry(ace, alloc->acl) {
+		if (richace_is_inherit_only(ace))
+			continue;
+		if (richace_is_everyone(ace)) {
+			if (richace_is_allow(ace))
+				allowed |= (ace->e_mask & ~denied);
+			else if (richace_is_deny(ace))
+				denied |= (ace->e_mask & ~allowed);
+			else
+				continue;
+			if (richace_change_mask(alloc, &ace, 0))
+				return -1;
+		} else {
+			if (richace_is_allow(ace)) {
+				if (richace_change_mask(alloc, &ace, allowed |
+						(ace->e_mask & ~denied)))
+					return -1;
+			} else if (richace_is_deny(ace)) {
+				if (richace_change_mask(alloc, &ace, denied |
+						(ace->e_mask & ~allowed)))
+					return -1;
+			}
+		}
+	}
+	if (allowed & ~RICHACE_POSIX_ALWAYS_ALLOWED) {
+		struct richace *last_ace = ace - 1;
+
+		if (alloc->acl->a_entries &&
+		    richace_is_everyone(last_ace) &&
+		    richace_is_allow(last_ace) &&
+		    richace_is_inherit_only(last_ace) &&
+		    last_ace->e_mask == allowed)
+			last_ace->e_flags &= ~RICHACE_INHERIT_ONLY_ACE;
+		else {
+			if (richacl_insert_entry(alloc, &ace))
+				return -1;
+			ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
+			ace->e_flags = RICHACE_SPECIAL_WHO;
+			ace->e_mask = allowed;
+			ace->e_id.special = RICHACE_EVERYONE_SPECIAL_ID;
+		}
+	}
+	return 0;
+}