| Message ID | 1441448856-13478-11-git-send-email-agruenba@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Sep 05, 2015 at 12:27:05PM +0200, Andreas Gruenbacher wrote: > A richacl roughly grants a requested access if the NFSv4 acl in the > richacl grants the requested permissions according to the NFSv4 > permission check algorithm and the file mask that applies to the process > includes the requested permissions. > > Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> > Acked-by: "J. Bruce Fields" <bfields@fieldses.org> > --- > fs/Makefile | 2 +- > fs/richacl_inode.c | 147 ++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/richacl.h | 3 + > 3 files changed, 151 insertions(+), 1 deletion(-) > create mode 100644 fs/richacl_inode.c > > diff --git a/fs/Makefile b/fs/Makefile > index ddc43d8..1305047 100644 > --- a/fs/Makefile > +++ b/fs/Makefile > @@ -48,7 +48,7 @@ obj-$(CONFIG_SYSCTL) += drop_caches.o > > obj-$(CONFIG_FHANDLE) += fhandle.o > obj-$(CONFIG_FS_RICHACL) += richacl.o > -richacl-y := richacl_base.o > +richacl-y := richacl_base.o richacl_inode.o > > obj-y += quota/ > > diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c > new file mode 100644 > index 0000000..ba05993 > --- /dev/null > +++ b/fs/richacl_inode.c > @@ -0,0 +1,147 @@ > +/* > + * Copyright (C) 2010 Novell, Inc. > + * Copyright (C) 2015 Red Hat, Inc. > + * Written by Andreas Gruenbacher <agruen@kernel.org> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License as published by the > + * Free Software Foundation; either version 2, or (at your option) any > + * later version. > + * > + * This program is distributed in the hope that it will be useful, but > + * WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + * General Public License for more details. > + */ > + > +#include <linux/sched.h> > +#include <linux/module.h> > +#include <linux/fs.h> > +#include <linux/slab.h> > +#include <linux/richacl.h> > + > +/** > + * richacl_permission - richacl permission check algorithm > + * @inode: inode to check > + * @acl: rich acl of the inode > + * @want: requested access (MAY_* flags) > + * > + * Checks if the current process is granted @mask flags in @acl. > + */ > +int > +richacl_permission(struct inode *inode, const struct richacl *acl, > + int want) > +{ > + const struct richace *ace; > + unsigned int mask = richacl_want_to_mask(want); > + unsigned int requested = mask, denied = 0; > + int in_owning_group = in_group_p(inode->i_gid); > + int in_owner_or_group_class = in_owning_group; > + > + /* > + * A process is > + * - in the owner file class if it owns the file, > + * - in the group file class if it is in the file's owning group or > + * it matches any of the user or group entries, and > + * - in the other file class otherwise. > + * The file class is only relevant for determining which file mask to > + * apply, which only happens for masked acls. > + */ > + if (acl->a_flags & RICHACL_MASKED) { > + if ((acl->a_flags & RICHACL_WRITE_THROUGH) && > + uid_eq(current_fsuid(), inode->i_uid)) { > + denied = requested & ~acl->a_owner_mask; > + goto out; > + } > + } else { > + /* > + * When the acl is not masked, there is no need to determine if > + * the process is in the group class and we can break out > + * earlier of the loop below. > + */ > + in_owner_or_group_class = 1; > + } > + > + /* > + * Check if the acl grants the requested access and determine which > + * file class the process is in. > + */ > + richacl_for_each_entry(ace, acl) { > + unsigned int ace_mask = ace->e_mask; > + > + if (richace_is_inherit_only(ace)) > + continue; > + if (richace_is_owner(ace)) { > + if (!uid_eq(current_fsuid(), inode->i_uid)) > + continue; > + goto entry_matches_owner; > + } else if (richace_is_group(ace)) { > + if (!in_owning_group) > + continue; > + } else if (richace_is_unix_user(ace)) { > + if (!uid_eq(current_fsuid(), ace->e_id.uid)) > + continue; > + } else if (richace_is_unix_group(ace)) { > + if (!in_group_p(ace->e_id.gid)) > + continue; > + } else > + goto entry_matches_everyone; > + > + /* > + * Apply the group file mask to entries other than owner@ and > + * everyone@ or user entries matching the owner. This ensures > + * that we grant the same permissions as the acl computed by > + * richacl_apply_masks(). > + * > + * Without this restriction, the following richacl would grant > + * rw access to processes which are both the owner and in the > + * owning group, but not to other users in the owning group, > + * which could not be represented without masks: > + * > + * owner:rw::mask > + * group@:rw::allow > + */ > + if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace)) > + ace_mask &= acl->a_group_mask; I'm having trouble understanding this. I think the problem is that I don't really understand the notation in your example. Is a_group_mask zero in that example? I think it must be, in which case, OK I think I get it. (Though I still have to think about it a little more to convince myself that richacl_apply_masks() always gets the same result.) --b. > + > +entry_matches_owner: > + /* The process is in the owner or group file class. */ > + in_owner_or_group_class = 1; > + > +entry_matches_everyone: > + /* Check which mask flags the ACE allows or denies. */ > + if (richace_is_deny(ace)) > + denied |= ace_mask & mask; > + mask &= ~ace_mask; > + > + /* > + * Keep going until we know which file class > + * the process is in. > + */ > + if (!mask && in_owner_or_group_class) > + break; > + } > + denied |= mask; > + > + if (acl->a_flags & RICHACL_MASKED) { > + /* > + * The file class a process is in determines which file mask > + * applies. Check if that file mask also grants the requested > + * access. > + */ > + if (uid_eq(current_fsuid(), inode->i_uid)) > + denied |= requested & ~acl->a_owner_mask; > + else if (in_owner_or_group_class) > + denied |= requested & ~acl->a_group_mask; > + else { > + if (acl->a_flags & RICHACL_WRITE_THROUGH) > + denied = requested & ~acl->a_other_mask; > + else > + denied |= requested & ~acl->a_other_mask; > + } > + } > + > +out: > + return denied ? -EACCES : 0; > +} > +EXPORT_SYMBOL_GPL(richacl_permission); > diff --git a/include/linux/richacl.h b/include/linux/richacl.h > index e00f313..9768eeb 100644 > --- a/include/linux/richacl.h > +++ b/include/linux/richacl.h > @@ -300,4 +300,7 @@ extern unsigned int richacl_want_to_mask(unsigned int); > extern void richacl_compute_max_masks(struct richacl *); > extern struct richacl *richacl_chmod(struct richacl *, mode_t); > > +/* richacl_inode.c */ > +extern int richacl_permission(struct inode *, const struct richacl *, int); > + > #endif /* __RICHACL_H */ > -- > 2.4.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2015-09-11 23:16 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>: > On Sat, Sep 05, 2015 at 12:27:05PM +0200, Andreas Gruenbacher wrote: >> + /* >> + * Apply the group file mask to entries other than owner@ and >> + * everyone@ or user entries matching the owner. This ensures >> + * that we grant the same permissions as the acl computed by >> + * richacl_apply_masks(). >> + * >> + * Without this restriction, the following richacl would grant >> + * rw access to processes which are both the owner and in the >> + * owning group, but not to other users in the owning group, >> + * which could not be represented without masks: >> + * >> + * owner:rw::mask >> + * group@:rw::allow >> + */ >> + if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace)) >> + ace_mask &= acl->a_group_mask; > > I'm having trouble understanding this. I think the problem is that I > don't really understand the notation in your example. Is a_group_mask > zero in that example? I think it must be, in which case, OK I think I > get it. Yes. I'm not sure if the example becomes easier to understand when the empty group mask and perhaps also the other mask is included. > (Though I still have to think about it a little more to convince myself > that richacl_apply_masks() always gets the same result.) I have tried to break the algorithm into digestible pieces. Do you see another way to make things easier to understand? Thanks, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Sep 12, 2015 at 12:12:16AM +0200, Andreas Grünbacher wrote: > 2015-09-11 23:16 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>: > > On Sat, Sep 05, 2015 at 12:27:05PM +0200, Andreas Gruenbacher wrote: > >> + /* > >> + * Apply the group file mask to entries other than owner@ and > >> + * everyone@ or user entries matching the owner. This ensures > >> + * that we grant the same permissions as the acl computed by > >> + * richacl_apply_masks(). > >> + * > >> + * Without this restriction, the following richacl would grant > >> + * rw access to processes which are both the owner and in the > >> + * owning group, but not to other users in the owning group, > >> + * which could not be represented without masks: > >> + * > >> + * owner:rw::mask > >> + * group@:rw::allow > >> + */ > >> + if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace)) > >> + ace_mask &= acl->a_group_mask; > > > > I'm having trouble understanding this. I think the problem is that I > > don't really understand the notation in your example. Is a_group_mask > > zero in that example? I think it must be, in which case, OK I think I > > get it. > > Yes. I'm not sure if the example becomes easier to understand when the > empty group mask and perhaps also the other mask is included. I think it would have been for me. In general I find it confusing to present the mask bits as additional ACEs--they're really pretty different. > > (Though I still have to think about it a little more to convince myself > > that richacl_apply_masks() always gets the same result.) > > I have tried to break the algorithm into digestible pieces. Do you see > another way to make things easier to understand? I just haven't reread those carefully enough yet, working on it.... --b. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/Makefile b/fs/Makefile index ddc43d8..1305047 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -48,7 +48,7 @@ obj-$(CONFIG_SYSCTL) += drop_caches.o obj-$(CONFIG_FHANDLE) += fhandle.o obj-$(CONFIG_FS_RICHACL) += richacl.o -richacl-y := richacl_base.o +richacl-y := richacl_base.o richacl_inode.o obj-y += quota/ diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c new file mode 100644 index 0000000..ba05993 --- /dev/null +++ b/fs/richacl_inode.c @@ -0,0 +1,147 @@ +/* + * Copyright (C) 2010 Novell, Inc. + * Copyright (C) 2015 Red Hat, Inc. + * Written by Andreas Gruenbacher <agruen@kernel.org> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2, or (at your option) any + * later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ + +#include <linux/sched.h> +#include <linux/module.h> +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/richacl.h> + +/** + * richacl_permission - richacl permission check algorithm + * @inode: inode to check + * @acl: rich acl of the inode + * @want: requested access (MAY_* flags) + * + * Checks if the current process is granted @mask flags in @acl. + */ +int +richacl_permission(struct inode *inode, const struct richacl *acl, + int want) +{ + const struct richace *ace; + unsigned int mask = richacl_want_to_mask(want); + unsigned int requested = mask, denied = 0; + int in_owning_group = in_group_p(inode->i_gid); + int in_owner_or_group_class = in_owning_group; + + /* + * A process is + * - in the owner file class if it owns the file, + * - in the group file class if it is in the file's owning group or + * it matches any of the user or group entries, and + * - in the other file class otherwise. + * The file class is only relevant for determining which file mask to + * apply, which only happens for masked acls. + */ + if (acl->a_flags & RICHACL_MASKED) { + if ((acl->a_flags & RICHACL_WRITE_THROUGH) && + uid_eq(current_fsuid(), inode->i_uid)) { + denied = requested & ~acl->a_owner_mask; + goto out; + } + } else { + /* + * When the acl is not masked, there is no need to determine if + * the process is in the group class and we can break out + * earlier of the loop below. + */ + in_owner_or_group_class = 1; + } + + /* + * Check if the acl grants the requested access and determine which + * file class the process is in. + */ + richacl_for_each_entry(ace, acl) { + unsigned int ace_mask = ace->e_mask; + + if (richace_is_inherit_only(ace)) + continue; + if (richace_is_owner(ace)) { + if (!uid_eq(current_fsuid(), inode->i_uid)) + continue; + goto entry_matches_owner; + } else if (richace_is_group(ace)) { + if (!in_owning_group) + continue; + } else if (richace_is_unix_user(ace)) { + if (!uid_eq(current_fsuid(), ace->e_id.uid)) + continue; + } else if (richace_is_unix_group(ace)) { + if (!in_group_p(ace->e_id.gid)) + continue; + } else + goto entry_matches_everyone; + + /* + * Apply the group file mask to entries other than owner@ and + * everyone@ or user entries matching the owner. This ensures + * that we grant the same permissions as the acl computed by + * richacl_apply_masks(). + * + * Without this restriction, the following richacl would grant + * rw access to processes which are both the owner and in the + * owning group, but not to other users in the owning group, + * which could not be represented without masks: + * + * owner:rw::mask + * group@:rw::allow + */ + if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace)) + ace_mask &= acl->a_group_mask; + +entry_matches_owner: + /* The process is in the owner or group file class. */ + in_owner_or_group_class = 1; + +entry_matches_everyone: + /* Check which mask flags the ACE allows or denies. */ + if (richace_is_deny(ace)) + denied |= ace_mask & mask; + mask &= ~ace_mask; + + /* + * Keep going until we know which file class + * the process is in. + */ + if (!mask && in_owner_or_group_class) + break; + } + denied |= mask; + + if (acl->a_flags & RICHACL_MASKED) { + /* + * The file class a process is in determines which file mask + * applies. Check if that file mask also grants the requested + * access. + */ + if (uid_eq(current_fsuid(), inode->i_uid)) + denied |= requested & ~acl->a_owner_mask; + else if (in_owner_or_group_class) + denied |= requested & ~acl->a_group_mask; + else { + if (acl->a_flags & RICHACL_WRITE_THROUGH) + denied = requested & ~acl->a_other_mask; + else + denied |= requested & ~acl->a_other_mask; + } + } + +out: + return denied ? -EACCES : 0; +} +EXPORT_SYMBOL_GPL(richacl_permission); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index e00f313..9768eeb 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -300,4 +300,7 @@ extern unsigned int richacl_want_to_mask(unsigned int); extern void richacl_compute_max_masks(struct richacl *); extern struct richacl *richacl_chmod(struct richacl *, mode_t); +/* richacl_inode.c */ +extern int richacl_permission(struct inode *, const struct richacl *, int); + #endif /* __RICHACL_H */