Hi Michael, On Sun, Feb 7, 2016 at 5:35 PM, Michael Kerrisk (man-pages) <mtk.manpages@xxxxxxxxx> wrote: > Hi Andreas, > > I'll probably have quite a few more comments on this page as I get to > understand RichACLs better. Here's some comments from an initial > reading. thanks a lot for all the feedback to the man-pages. I've more or less made all the suggested changes but didn't get to adding examples yet (that's not so easy). The changes are here: https://github.com/andreas-gruenbacher/richacl > So, an initial comment. It seems to me to that this page (but > not setrichacl(1) and getrichacl(1)) should ultimately land in > man-pages (just like acl(7)), since we're talking about a kernel > feature. Make sense? We could sure move acl(5) and richacl(7) there. >> .\" >> .\" Richacl Manual Pages >> .\" >> .\" Copyright (C) 2015 Red Hat, Inc. >> .\" Written by Andreas Gruenbacher <agruenba@xxxxxxxxxx> >> .\" This is free documentation; 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 of >> .\" the License, or (at your option) any later version. >> .\" >> .\" The GNU General Public License's references to "object code" >> .\" and "executables" are to be interpreted as the output of any >> .\" document formatting or typesetting system, including >> .\" intermediate and printed output. >> .\" >> .\" This manual 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. >> .\" >> .\" You should have received a copy of the GNU General Public >> .\" License along with this manual. If not, see >> .\" <http://www.gnu.org/licenses/>. >> .\" >> .de URL >> \\$2 \(laURL: \\$1 \(ra\\$3 >> .. >> .if \n[.g] .mso www.tmac >> .TH RICHACL 7 2015-09-01 "Linux" "Rich Access Control Lists" >> .SH NAME >> richacl \- Rich Access Control Lists >> .SH DESCRIPTION >> Rich Access Control Lists (richacls) are an extension of the POSIX file > > For what it's worth, I think it would be worthwhile to start with > a consistent abbreviation comment here (and use it throughout all of the > man pages): "RichACL" (or "richACL"), rather than "richacl"; that seems > more consistent with the traditional abbreviation "ACL". > >> permission model to support > > Make this: > > permission mode (see > .BR acl (7)) > to support > >> .URL https://tools.ietf.org/rfc/rfc5661.txt "NFSv4 Access Control Lists" >> on local and remote-mounted filesystems. >> >> Richacls support file masks which allow to apply a file mode to an existing > > s/which allow to apply/which can be used to apply/ > >> NFSv4 ACL without destructive side effects: the file mode determines the values >> of the file masks; the file masks restrict the permissions granted by the NFSv4 >> ACL. When a less restrictive file mode is applied later, the file masks become >> less restrictive, and more of the original permissions can become effective. >> >> A richacl can always be translated into an equivalent NFSv4 ACL which grants >> the same permissions. >> >> Richacls can be enabled on supported filesystems. This disables POSIX Access >> Control Lists; the two ACL models will not coexist on the same filesystem. > > s/will not/can not/ ? > >> >> When used on a filesystem that does not support richacls, the getrichacl and > > Use > .BR getrichacl (1) > for cross-references. > >> setrichacl utilities will operate on the file permission bits instead: >> getrichacl will display the file permission bits as a richacl; when a richacl > > Use > .BR getrichacl (1) > for cross-references. > >> is set with setrichacl which can be represented exactly by the file permission > > Use > .BR setrichacl (1) > for cross-references. > >> bits, setrichacl will set the file permission bits instead. > > Use > .BR setrichacl (1) > for cross-references. > > Here, I think it would be helpful to add a sentence: > > "An attempt to set a richacl that cannot be represented exactly by the > file permission bits results in an error." > > (If that sentence is correct, of course.) > >> >> .SH STRUCTURE OF RICHACLS > > For all of the "nonstandard" (see man-pages(7)) ".SH" sections here, I'd > be inclined to switch to using ".SS" subsections. There are downsides to > multiple nonstandard section headings (e.g., automated TOCs for > Section headings become clumsy and long), and I don't think your use of > .SH vs .SS really helps much to structure the information in this page. > >> >> Richacls consist of a number of ACL entries, three file masks, and some flags. > > s/some flags./some flags specifying attributes of the ACL as whole (by > contrast with the per-ACL-entry flags described below)./ > >> Each of the ACL entries allows or denies some permissions to a particular user, >> group, or special entity. Each acl entry consists of: > > s/acl// > >> .IP \(bu 4 >> The user (with prefix > > s/The user/A tag which specifies the user/ > > (Is "tag" the right word? In any case, what would helpful to have here > is the generic term for this component of the ACL.) Tag should do; I'm not aware of a better term. >> .B user: >> or >> .BR u: ), >> group (with prefix >> .B group: >> or >> .BR g: ), >> or special identifier the entry applies to. Special >> identifiers can be the file owner >> .RB ( owner@ ), >> the owning group >> .RB ( group@ ), >> or everyone >> .RB ( everyone@ ). >> .IP \(bu >> A set of permissions the entry allows or denies. >> .IP \(bu >> A set of flags that indicate whether the user or group identifier is mapped or >> unmapped, and whether the entry has been and can be inherited. >> .IP \(bu 4 >> A field indicating whether the entry allows or denies access. >> .PP >> The owner, group, and other file masks further control which permissions the >> ACL grants, subject to the >> .B masked >> .RB ( m ) >> and >> .B write_through >> .RB ( w ) >> ACL flags. >> >> Note that entries with the identifier >> .B everyone@ >> apply to all processes, whereas the \(lqother\(rq file permissions and >> \(lqother\(rq entries in POSIX ACLs apply to all processes which are not the >> owner, are not in the owning group, and do not match a user or group mentioned >> in the acl. > > s/acl/ACL/ > >> Richacls do not have separate \(lqaccess\(rq ACLs that define the access >> permissions and \(lqdefault\(rq ACLs that define the inheritable permissions as >> POSIX ACLs. > > I'd restructure the preceding sentence as: > > "Unlike POSIX ACLs, richacls do not.... that define the inheritable > permissions." > >> Instead, whether an ACL entry is effective during access checks >> and/or inheritable is determined by the ACL entry flags. >> >> .SS ACL Flags > > I'd use lower case in the above for all words except the first. > (That's the convention in man-pages.) > >> The following flags on ACLs are defined: >> >> .RS 4 >> .HP 4 > > s/4/8/ in the preceding two lines. I think more indentation would make > this (and the similar lists below) more readable. > >> .B masked >> .RB ( m ): > > I'd write each of these list entries starting here, and below, in the > form: > > .BR masked "\ (" m ): > > This form is a little easier to read in the source, and > it forces just a single space before the "(", which looks > a little better, I find. > >> When set, the file masks define upper limits on the permissions the ACL may >> grant. >> .HP >> .B write_through >> .RB ( w ): >> When this flag and the masked flag are both set, the owner and other file masks > > .B masked > >> define the actual permissions granted to the file owner and to others instead >> of an upper limit. >> .HP >> .B auto_inherit >> .RB ( a ): >> Automatic Inheritance is enabled for the file the ACL is >> attached to. See >> .IR "Automatic Inheritance" . >> .HP >> .B protected >> .RB ( p ): >> The ACL is protected from modification by Automatic >> Inheritance. >> .HP >> .B defaulted >> .RB ( d ): >> The ACL has been assigned by default. Automatic Inheritance should completely >> replace the ACL. >> .RE >> >> .SS ACL Entry Flags >> >> The following flags on ACL entries are defined: >> >> .RS 4 >> .HP 4 > > s/4/8/ in the preceding two lines. > >> .B file_inherit >> .RB ( f ): >> The entry is inheritable for files. >> .HP >> .B dir_inherit >> .RB ( d ): >> The entry is inheritable for directories. >> .HP >> .B no_propagate >> .RB ( n ): >> Inheritance stops at the next subdirectory level. >> .HP >> .B inherit_only >> .RB ( i ): >> The entry defines inheritable permissions only and is ignored for access >> checking. >> .HP >> .B inherited >> .RB ( a ): >> The entry has been automatically inherited from the parent directory; the >> ACL's auto_inherit > > Use > .B auto_inherit > >> .RB ( a ) >> flag should be on. >> .HP >> .B unmapped >> .RB ( u ): >> The user or group identifier is a textual string and has no mapping to a >> numeric user or group identifier. > > So here, I think there should be a sentence that explains how a meaning > is attached to the strings? Is this for NFS, for Windows, for something > else? On NFS clients only. I've tried to clarify that. >> .RE >> >> .SS Permissions >> >> The following permissions are defined for richacl entries and for the three >> file masks: >> >> .RS 4 >> .HP 4 > > s/4/8/ in the preceding two lines. > >> .B read_data >> / >> .B list_directory >> .RB ( r ): > > Replace the preceding four lines by > > .BR read_data / list_directory "\ (" r ) > > and do similar for the next two list entried below. > Note that "\ (" will force just a singlke space before the "(". > >> Read the data of a file. >> List the contents of a directory. > > In the above list entry, and the next two, I find the layout ("xxx/yyy (z)") > confusing. A closer reading indicates that in each case, the "xxx" > applies for files and he "yyy" is for directories. But I think the text > could make this point a little easier to grasp. In each of these three > list entries this could be done something lke the following: > > "For a file: read the data of the file. For a directory: list the > contents of the directory." > > By the way, can the terms "read_data" and "list_directory" be used > interchangeably? That is, can you employ (say) "read_data" when setting > an ACL entry for a directory? (I'm assuming the answer is "yes".) > If the terms are just interchangeable synonyms, perhas it's worth > making that point explicitly in the text. richacl_from_text() doesn't distinguish between file and directory flags, but richacl_to_text() will use the appropriate version in long-format strings depending on the context (file type). ACLs that have this wrong would be very confusing to read. >> .HP >> .B write_data >> / >> .B add_file >> .RB ( w ): >> Modify the data of a file. Add a new file in a directory. > > See above comment re file/directory. > >> .HP >> .B append_data >> / >> .B add_subdirectory >> .RB ( p ): >> Open a file in append mode. Create a subdirectory in a directory. > > So, in other words, if append mode is denied, then the file can be > opened for writing (contingent on write permission being granted), but > can't be opened with O_APPEND? Is that correct? This point needs to be > made clearer. Yes, that's correct. >> .HP >> .B execute >> .RB ( x ): >> Execute a file. Traverse / search a directory. > > See above comment re file/directory. > >> .HP >> .B delete_child >> .RB ( d ): >> Delete a file or directory within a directory. >> .HP >> .B delete >> .RB ( D ): >> Delete the file or directory. >> .HP >> .B read_attributes >> .RB ( a ): >> Read basic attributes of a file or directory. > > What are "attributes" in this context? Does this mean stat(2)? Make this > explicit. Yes. >> This permission is always implicitly granted. >> .HP >> .B write_attributes >> .RB ( A ): >> Change the times associated with a file or directory to an arbitrary value. >> This permission is always implicitly granted to the file owner. >> .HP >> .B read_acl >> .RB ( c ): >> Read the ACL of a file or directory. This permission is always >> implicitly granted. >> .HP >> .B write_acl >> .RB ( C ): >> Change the ACL or file mode of a file or directory. >> .HP >> .B write_owner >> .RB ( o ): >> Take ownership of a file or directory. Change the owning group of a file or >> directory to a group of which the calling process is a member. >> .HP >> .B read_named_attrs >> .RB ( R ), >> .B write_named_attrs >> .RB ( W ), >> .B synchronize >> .RB ( S ), >> .B write_retention >> .RB ( e ), >> .B write_retention_hold >> .RB ( E ): >> These permissions can be stored, but do not have a local meaning. > > So, I thenk that a sentence here should explain why these permissions > exist. Is if for future extension, because they are meaningful in NFS, > or something else? Yes, they are defined by NFS. >> .RE >> >> .SH TEXT FORM >> >> The common textual representation of richacl consists of the colon separated > > s/richacl/richacls/ (or, "RichACLs"/"richACLs") > > s/colon separated/colon-separated/ > >> fields of the the acl flags, file masks, and acl entries in the following > > s/acl/ACL/ (*2) > >> format: >> .TP >> \fBflags:\fR\fIacl_flags\fR >> The ACL flags. >> .TP >> \fBowner:\fR\fIperm\fR\fB::mask\fR, \fBgroup:\fR\fIperm\fR\fB::mask\fR, \fBother:\fR\fIperm\fR\fB::mask\fR >> The file masks and their permissions. >> .TP >> \fIwho\fR\fB:\fR\fIperm\fR\fB:\fR\fIflags\fR\fB:allow\fR, \fIwho\fR\fB:\fR\fIperm\fR\fB:\fR\fIflags\fR\fB:deny\fR >> For each ACL entry, who the entry applies to, the permissions of the entry, the >> entry flags, and whether the entry allows or denies permissions. The who field has > > s/who/\\fIwho\\fP/ > >> no prefix for special identifiers, a >> .B user: >> or >> .B u: >> prefix for regular users, and a >> .B group: >> or >> .B g: >> prefix for regular groups. >> .PP >> The entries are comma, whitespace or newline separated. > > s/whitespace/whitespace,/ > >> >> Flags and permissions have single-letter as well as long forms as listed under > > s/forms/forms,/ > >> .IR "ACL Flags" , >> .IR "ACL Entry Flags" , >> and >> .IR Permissions . > > If you follow my suggestion about capitalization in the ".SS" entries, > you'll need to change the capitalization in the above phrases. > >> When the single-letter forms are used, the flags or permissions are >> concatenated. When the long forms are used, the flags or permissions are >> separated by slashes. To align permissions or flags vertically, dashes can be >> use for padding. > > s/use/used/ > >> >> .SH SETTING AND MODIFYING FILE PERMISSIONS >> The access permissions for a file can either be set by assigning an access >> control list (setrichacl) or by changing the file mode permission bits (chmod). > > Use > .RB ( setrichacl (1)) > for cross-reference. > > Use > .RB ( chmod (1)). > >> In addition, a file can inherit an ACL from its parent >> directory at create time; the inherited ACL is then further > > s/create/creation/ > >> restricted by the creating system call's mode parameter (see the creat(2) >> manual page). > > creat(2) is pretty much history. I suggest writing > > (as given to > .BR open (2), > .BR mkdir (2), > and similar). > > And here, I think we need a statement about whether the process umask > has an effect or not... > >> >> .SS Assigning An Access Control List >> When assigning an ACL to a file, unless explicitly specified, the owner, group, >> and other file masks will be computed from the ACL entries as described in >> section >> .IR "COMPUTING THE MAXIMUM FILE MASKS" . >> The owner, group, and other file mode permission bits are then each set from >> the owner, group, and other file mask as follows: >> .IP \(bu 4 >> If the file mask includes the >> .B r >> permission, the read >> file mode permission bit will be set. >> .IP \(bu >> If the file mask includes the >> .B w >> or >> .B p >> permission, the write file mode permission bit will be set. >> .IP \(bu >> If the file mask includes the >> .B x >> permission, the execute file mode permission bit will be set. >> .PP >> If the ACL can be represented exactly by the file mode >> permission bits, the file permission bits are set to match the access control >> list and the ACL is not stored. (When the reverse happens and > > s/and/and the/ > >> ACL of a file is requested which doesn't have an explicit >> ACL, the file mode permission bits are converted into an >> equivalent richacl.) >> >> .SS Changing The File Mode Permission Bits > > I'd use lower case in the above for all words except the first > >> When changing the file mode permission bits with chmod(2), the owner, group, > > .BR chmod (2) > >> and other file permission bits are set to the permission bits in the new mode, >> and the file masks each are set based on the new mode bits as follows: >> .IP \(bu 4 >> If the read bit in a set of permissions is set, the >> .B r >> permission in the corresponding file mask will be set. >> .IP \(bu >> If the write bit in a set of permissions is set, the >> .B w >> and >> .B p >> permissions in the corresponding file mask will be set. >> .IP \(bu >> If the execute bit in a set of permissions is set, the >> .B x >> permission in the corresponding file mask will be set. >> .PP >> In addition, the >> .B masked >> and >> .B write_through >> ACL flags are set. This has the >> effect of limiting the permissions granted by the ACL to the file mode >> permission bits; in addition, the owner is granted the owner mode bits and >> others are granted the other mode bits. If the >> .B auto_inherit >> flag is set, the >> .B protected >> flag is also set to prevent the Automatic Inheritance algorithm from modifying >> the ACL. >> >> .SS Permissions At File Create Time > > s/File Create/file-creation/ > > I'd use lower case in the above for all words except the first > >> When a directory has inheritable ACL entries, the following >> happens when a file or directory is created inside that directory: >> .RS 4 >> .IP 1. 4 >> A file created inside that directory will inherit all entries with the > > s/all entries with/all of the directories entries that/ It's ACL entries, not directory entries, here. >> .B file_inherit >> flag set, and all inheritance-related flags in the inherited entries will be >> cleared. >> >> A subdirectory will inherit all entries with the >> .B file_inherit >> or >> .B dir_inherit >> flag set. Entries whose >> .B no_propagate >> flag is set will have all inheritance-related flags cleared. Entries whose >> .B no_propagate >> and >> .B dir_inherit >> flags are not set and whose >> .B file_inherit >> is set will have their >> .B inherit_only >> flag set. >> .IP 2. >> If the parent directory's ACL has the >> .B auto_inherit >> flag set, the inherited ACL will have its >> .B auto_inherit >> flag set, and all entries will have their >> .B inherited >> flag set. >> .IP 3. >> The three file masks are computed from the inherited ACL as described in >> section >> .IR "COMPUTING THE MAXIMUM FILE MASKS" . >> .IP 4. >> The three sets of permissions for the owner, the group, and for others in >> the mode parameter of the creating system call are converted into sets of >> richacl permissions as described in section > > s/in/in the/ > >> .IR "Changing The File Mode Permission Bits" . >> Any richacl permissions not included in those sets are >> removed from the owner, group, and other file masks. The file mode permission >> bits are then computed from the file masks as described in section > > s/in/in the/ > >> .IR "Assigning An Access Control List" . >> .IP 5. >> The >> .B masked >> ACL flag is set. The >> .B write_through >> ACL flag remains cleared. In addition, if the >> .B auto_inherit >> flag of the inherited ACL is set, the >> .B protected >> flag is also set to prevent the Automatic Inheritance algorithm from modifying >> the ACL. >> .RE >> .PP >> When a directory does not have inheritable ACL entries, files >> and directories created inside that directory will not be assigned access >> control lists and the file mode permission bits will be set to (mode\ &\ >> ~umask). > > will be set to > > (mode & ~umask) > > where > .I mode > is the permission mode argument of the relevant system call and > .I umask > is the process umask (see > .BR umask (2)). > >> >> .SS Automatic Inheritance > > I'd use lower case in the above for all words except the first "Automatic Inheritance" is a technical term though. >> Automatic Inheritance allows permission changes to propagate from a directory >> to files and subdirectories inside that directory, recursively. Carrying out >> this propagation of permissions is the responsibility of the process changing >> the directory permissions (usually, setrichacl(1)). > > I'm confused by the previous sentence. the feature is labeled "Automatic > Inheritance", implying that the user/process need do nothing. The next > sentence says "propagation ... is the responsibility of the process". > These two points seem contradictory. I think something more needs to be > said here. Let's try this maybe: Automatic Inheritance is a mechanism that allows permission changes to propagate from a directory to files and subdirectories inside that directory, recursively. Propagation is carried out by the process changing the directory permissions (usually, .BR setrichacl (1)); it happens without user intervention albeit not entirely automatically. >> A significant limitation is that this mechanism works only as long as files >> are created without explicitly specifying the file permissions to use. The >> standard system calls for creating files an directories (creat(2), open(2), >> mkdir(2), mkfifo(2), mknod(2)) all have mandatory mode parameters which define > > Format that system call list as > .RB ( creat (2), > .BR open (2), > .BR mkdir (2), > .BR mknod (2)) > > Note that I removed mkfifo(): it's a library functionlayered on > mkonod(2). > >> the maximum allowed permissions of the new files. To take account of this >> restriction, the >> .B protected >> ACL flag must be set if the >> .B inherited >> flag is set. This effectively disables Automatic Inheritance for that >> particular file. >> >> Automatic Inheritance still remains useful for network protocols like NFSv4 and >> SMB, which both support creating files and directories without defining which >> permissions: they can implement those operations by using the standard system >> calls and by then undoing the effect of applying the mode parameters. >> >> When the ACL of a directory is changed, the following should > > Why "should"? > >> happen for each entry inside that directory (for each \(lqchild\(rq): > > Make the preceding line: > > happen for each entry (\(lqchild\(rq) inside that directory: > >> .IP 1. 4 >> If the entry is a symblic link, skip the child. >> .IP 2. >> If the >> .B auto_inherit >> flag of the entry's ACL is not set or the >> .B protected >> flag is set, skip the child. >> .IP 3. >> With the child's ACL: >> .RS 4 >> .IP 1. 4 > > s/1./a)/ > > (i.e., use a different labeling scheme for the sublist) > >> If the >> .B defaulted >> flag is set, replace the ACL with an empty ACL >> with the >> .B auto_inherit >> flag set. >> .IP 2. > > s/2./b)/ > >> Delete all entries which have the >> .B inherited >> flag set. >> .IP 3. > > s/3./c)/ > >> Append all entries inherited from the parent directory according to step 1 of >> the algorithm described under >> .IR "Permissions At File Create Time". >> Set the >> .B inherited >> flag of each of these entries. >> .IP 4. > > s/4./d)/ > >> Recompute the file masks. >> .RE >> .IP 4. >> If the child is a directory, recursively apply this algorithm. >> >> .SH ACCESS CHECK ALGORITHM >> >> When a process requests a particular kind of access to a file defined by a set > > s/defined/protected/ (?) > >> of richacl permissions, the following algorithm determines if the access is > > s/if/whether/ > >> granted or denied: >> >> .IP 1. 4 >> If the >> .B masked >> ACL flag is set, then: >> .RS 4 >> .IP 1. 4 > > s/1./a)/ > > Use a different numbering scheme for sublists. > >> if the > > s/if/If/ > >> .B write_through >> ACL flag is set, then: >> .RS 4 >> .IP \(bu 4 >> if the requesting process is the file owner, then access is granted if the > > s/if/If/ > >> owner mask includes the requested permissions, and is otherwise denied. >> .IP \(bu >> if the requesting process is not the file owner, is not in the owning group, > > s/if/If/ > >> and no ACL entries other than >> .B everyone@ >> match the process, then access is granted if the other mask includes the >> requested permissions, and is otherwise denied. >> .RE >> .IP 2. > > s/2./b)/ > >> if any of the following is true: > > s/if/If/ > >> .RS 4 >> .IP \(bu 4 >> the requesting process is the file owner and the owner mask does no include all > > s/no /not / > >> requested permissions, >> .IP \(bu 4 >> the requesting process is not the file owner and it is in the owning group or >> matches any ACL entries other than >> .BR everyone@ , >> and the group mask does no include all requested permissions, >> .IP \(bu 4 >> the requesting process is not the file owner, not in the owning group, it >> matches no ACL entries other than >> .BR everyone@ , >> and the other mask does no include all requested permissions, >> .PP >> then access is denied. >> .RE >> .RE >> .IP 2. >> Set the remaining permissions to the requested permissions. Go through all ACL >> entries. For each entry: >> .RS 4 >> .IP 1. 4 > > s/1./a)/ > > Use a different numbering scheme for sublists. > >> if the >> .B inherit_only >> or >> .B unmapped >> flags are set, continue with the next ACL entry. >> .IP 2. > > s/2./b)/ > >> if any of the following is true: >> .RS 4 >> .IP \(bu 4 >> the entry's identifier is >> .B owner@ >> and the requesting process is the file owner, >> .IP \(bu >> the entry's identifier is >> .B group@ >> and the requesting process is in the owning group, >> .IP \(bu >> the entry's identifier is a user and the requesting process is owned by that >> user, >> .IP \(bu >> the entry's identifier is a group and the requesting process is a member in >> that group, >> .IP \(bu >> the entry's identifier is >> .BR everyone@ , >> .PP >> the entry matches the process; proceed. Otherwise, continue with the next ACL > > s/proceed/proceed to the next step/ (?) > >> entry. >> .RE >> .IP 3. > > s/3./c)/ > >> If the entry denies any of the remaining permissions, access is denied. >> .IP 4. > > s/4./d)/ > >> If the entry allows any of the remaining permissions, then: >> .RS 4 >> .IP \(bu 4 >> if the >> .B masked >> ACL flag is set and the entry's identifier is not >> .B owner@ >> or >> .BR everyone@ >> or is a user entry matching the file owner, remove all permissions from the >> remaining permissions which are both allowed by the entry and included in the >> group mask, >> .IP \(bu >> otherwise, remove all permissions from the remaining permissions wich are >> allowed by the entry. >> .RE >> .RE >> .IP 3. >> If there are no more remaining permissions, access is allowed. Otherwise, >> access is denied. >> >> .SH COMPUTING THE MAXIMUM FILE MASKS >> When setting an ACL and no file masks have been explicitly specified and when >> inheriting an ACL from the parent directory, the following algorithm is used >> for computing the file masks: >> >> .IP 1. 4 >> Clear the owner, group, and other file masks. Remember which permissions have >> already been processed (initially, the empty set). >> .IP 2. >> For each ACL entry: >> .RS 4 >> .IP \(bu 4 >> If the >> .B inherit_only >> flag is set, skip the entry. >> .IP \(bu 4 >> Otherwise, compute which permissions the entry allows or denies that have not >> been processed yet (the remaining permissions). >> .IP \(bu >> If the entry is an >> .B owner@ >> entry, add the remaining permissions to the owner mask for >> .B allow >> entries, and remove the remaining permissions from the owner mask for >> .B deny >> entries. >> .IP \(bu >> Otherwise, if the entry is an >> .B everyone@ >> entry, proceed as with >> .B owner@ >> entries but add or remove the remaining permissions from the owner, group, and >> other file masks. >> .IP \(bu >> Otherwise, proceed as with >> .B owner@ >> entries but add or remove the remaining permissions from the owner and group >> file masks. >> .IP \(bu >> Add the entry's permissions to the processed permissions. >> .RE >> .PP >> The resulting file masks represent the ACL as closely as possible. With these >> file masks, if the >> .B masked >> ACL flag is set, the effective permissions still stay the same. > > This page is in *desperate* need of *multiple* examples, starting simple, > and building up in complexity, with walkthogh text explaining how the > permisssions are interpreted and how the masks are generated. > Having read the page multiple times (and having little knowledge > of NFS ACLs), I'm still struggling to put all the pieces together. You are probably right. I'm not sure if they should go on the same man-page. > Probably some examples that relate to an NFS context would also be > helpful. Hmm, I'm not sure about the difference between NFS examples and non-NFS examples I suppose. >> .\" .SH BUGS >> .SH AUTHOR >> Written by Andreas Grünbacher <agruenba@xxxxxxxxxx>. >> >> Please send your bug reports, suggested features and comments to the above address. >> >> .SH CONFORMING TO >> Rich Access Control Lists are Linux-specific. >> .SH SEE ALSO >> .BR chmod (1), >> .BR getrichacl (1), >> .BR ls (1), >> .BR setrichacl (1) >> .BR stat (2), >> .BR umask (2), >> .BR acl (7) >> .\" librichacl Thanks a lot, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
