Moby currently sorts uid and gid ranges in id maps. This causes subuid
and subgid files to be interpreted wrongly.
The subuid file
```
> cat /etc/subuid
jonas:100000:1000
jonas:1000:1
```
configures that the container uids 0-999 are mapped to the host uids
100000-100999 and uid 1000 in the container is mapped to uid 1000 on the
host. The expected uid_map is:
```
> docker run ubuntu cat /proc/self/uid_map
0 100000 1000
1000 1000 1
```
Moby currently sorts the ranges by the first id in the range. Therefore
with the subuid file above the uid 0 in the container is mapped to uid
100000 on host and the uids 1-1000 in container are mapped to the uids
1-1000 on the host. The resulting uid_map is:
```
> docker run ubuntu cat /proc/self/uid_map
0 1000 1
1 100000 1000
```
The ordering was implemented to work around a limitation in Linux 3.8.
This is fixed since Linux 3.9 as stated on the user namespaces manpage
[1]:
> In the initial implementation (Linux 3.8), this requirement was
> satisfied by a simplistic implementation that imposed the further
> requirement that the values in both field 1 and field 2 of successive
> lines must be in ascending numerical order, which prevented some
> otherwise valid maps from being created. Linux 3.9 and later fix this
> limitation, allowing any valid set of nonoverlapping maps.
This fix changes the interpretation of subuid and subgid files which do
not have the ids of in the numerical order for each individual user.
This breaks users that rely on the current behaviour.
The desired mapping above - map low user ids in the container to high
user ids on the host and some higher user ids in the container to lower
user on host - can unfortunately not archived with the current
behaviour.
[1] http://man7.org/linux/man-pages/man7/user_namespaces.7.html
Signed-off-by: Jonas Dohse <jonas@dohse.ch>
This implements chown support on Windows. Built-in accounts as well
as accounts included in the SAM database of the container are supported.
NOTE: IDPair is now named Identity and IDMappings is now named
IdentityMapping.
The following are valid examples:
ADD --chown=Guest . <some directory>
COPY --chown=Administrator . <some directory>
COPY --chown=Guests . <some directory>
COPY --chown=ContainerUser . <some directory>
On Windows an owner is only granted the permission to read the security
descriptor and read/write the discretionary access control list. This
fix also grants read/write and execute permissions to the owner.
Signed-off-by: Salahuddin Khan <salah@docker.com>
This subtle bug keeps lurking in because error checking for `Mkdir()`
and `MkdirAll()` is slightly different wrt to `EEXIST`/`IsExist`:
- for `Mkdir()`, `IsExist` error should (usually) be ignored
(unless you want to make sure directory was not there before)
as it means "the destination directory was already there"
- for `MkdirAll()`, `IsExist` error should NEVER be ignored.
Mostly, this commit just removes ignoring the IsExist error, as it
should not be ignored.
Also, there are a couple of cases then IsExist is handled as
"directory already exist" which is wrong. As a result, some code
that never worked as intended is now removed.
NOTE that `idtools.MkdirAndChown()` behaves like `os.MkdirAll()`
rather than `os.Mkdir()` -- so its description is amended accordingly,
and its usage is handled as such (i.e. IsExist error is not ignored).
For more details, a quote from my runc commit 6f82d4b (July 2015):
TL;DR: check for IsExist(err) after a failed MkdirAll() is both
redundant and wrong -- so two reasons to remove it.
Quoting MkdirAll documentation:
> MkdirAll creates a directory named path, along with any necessary
> parents, and returns nil, or else returns an error. If path
> is already a directory, MkdirAll does nothing and returns nil.
This means two things:
1. If a directory to be created already exists, no error is
returned.
2. If the error returned is IsExist (EEXIST), it means there exists
a non-directory with the same name as MkdirAll need to use for
directory. Example: we want to MkdirAll("a/b"), but file "a"
(or "a/b") already exists, so MkdirAll fails.
The above is a theory, based on quoted documentation and my UNIX
knowledge.
3. In practice, though, current MkdirAll implementation [1] returns
ENOTDIR in most of cases described in #2, with the exception when
there is a race between MkdirAll and someone else creating the
last component of MkdirAll argument as a file. In this very case
MkdirAll() will indeed return EEXIST.
Because of #1, IsExist check after MkdirAll is not needed.
Because of #2 and #3, ignoring IsExist error is just plain wrong,
as directory we require is not created. It's cleaner to report
the error now.
Note this error is all over the tree, I guess due to copy-paste,
or trying to follow the same usage pattern as for Mkdir(),
or some not quite correct examples on the Internet.
[1] https://github.com/golang/go/blob/f9ed2f75/src/os/path.go
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
There is no case which would resolve in this error. The root user always exists, and if the id maps are empty, the default value of 0 is correct.
Signed-off-by: Daniel Nephin <dnephin@docker.com>
Change user/group creation to use flags to adduser/useradd to enforce it
being a system user. Use system user defaults that auto-create a
matching group. These changes allow us to remove all group creation
code, and in doing so we also removed the code that finds available uid,
gid integers and use post-creation query to gather the system-generated
uid and gid.
The only added complexity is that today distros don't auto-create
subordinate ID ranges for a new ID if it is a system ID, so we now need
to handle finding a free range and then calling the `usermod` tool to
add the ranges for that ID. Note that this requires the distro supports
the `-v` and `-w` flags on `usermod` for subordinate ID range additions.
Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
Since Docker is already skipping newlines in /etc/sub{uid,gid},
this patch skips commented out lines - otherwise Docker fails to start.
Add unit test also.
Signed-off-by: Antonio Murdaca <runcom@redhat.com>
This fixes errors in ownership on directory creation during build that
can cause inaccessible files depending on the paths in the Dockerfile
and non-existing directories in the starting image.
Add tests for the mkdir variants in pkg/idtools
Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
The `pkg/idtools` package supports the creation of user(s) for
retrieving /etc/sub{u,g}id ranges and creation of the UID/GID mappings
provided to clone() to add support for user namespaces in Docker.
Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
