[lxc-devel] [RFC 1/2] create_run_template: tell the template what caller's uid was mapped to
Stéphane Graber
stgraber at ubuntu.com
Tue Nov 5 20:21:11 UTC 2013
On Tue, Nov 05, 2013 at 02:14:33PM -0600, Serge Hallyn wrote:
> conf.c/conf.h: have replaced bool hostid_is_mapped() with int mapped_hostid()
> which returns the mapped uid for the caller's uid on the host, or -1 if
> none
>
> create_run_template: pass caller's uid into template.
>
> lxc-ubuntu-cloud:
> 1. accept --mapped-uid argument
> 2. don't write to devices cgroup - not allowed.
> 3. if running in userns, use $HOME/.cache
> 4. chown cached files to the uid to which our caller was
> mapped
> 5. ignore /dev when extracting rootfs in a userns
>
> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
There is just one info statement that looks a bit off a bit below, but
with that one dropped or properly indented:
Acked-by: Stéphane Graber <stgraber at ubuntu.com>
> ---
> src/lxc/conf.c | 6 +++---
> src/lxc/conf.h | 2 +-
> src/lxc/lxccontainer.c | 38 ++++++++++++++++++++++++++++++--------
> templates/lxc-ubuntu-cloud.in | 25 +++++++++++++++++++++++--
> 4 files changed, 57 insertions(+), 14 deletions(-)
>
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 2a47e77..afdaa14 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -2912,7 +2912,7 @@ uid_t get_mapped_rootid(struct lxc_conf *conf)
> return (uid_t)-1;
> }
>
> -bool hostid_is_mapped(int id, struct lxc_conf *conf)
> +int mapped_hostid(int id, struct lxc_conf *conf)
> {
> struct lxc_list *it;
> struct id_map *map;
> @@ -2921,9 +2921,9 @@ bool hostid_is_mapped(int id, struct lxc_conf *conf)
> if (map->idtype != ID_TYPE_UID)
> continue;
> if (id >= map->hostid && id < map->hostid + map->range)
> - return true;
> + return (id - map->hostid) + map->nsid;
> }
> - return false;
> + return -1;
> }
>
> int find_unmapped_nsuid(struct lxc_conf *conf)
> diff --git a/src/lxc/conf.h b/src/lxc/conf.h
> index 71399b9..940d493 100644
> --- a/src/lxc/conf.h
> +++ b/src/lxc/conf.h
> @@ -362,7 +362,7 @@ extern void lxc_rename_phys_nics_on_shutdown(struct lxc_conf *conf);
>
> extern uid_t get_mapped_rootid(struct lxc_conf *conf);
> extern int find_unmapped_nsuid(struct lxc_conf *conf);
> -extern bool hostid_is_mapped(int id, struct lxc_conf *conf);
> +extern int mapped_hostid(int id, struct lxc_conf *conf);
> extern int chown_mapped_root(char *path, struct lxc_conf *conf);
> extern int ttys_shift_ids(struct lxc_conf *c);
> #endif
> diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> index 946133d..594a96d 100644
> --- a/src/lxc/lxccontainer.c
> +++ b/src/lxc/lxccontainer.c
> @@ -916,20 +916,28 @@ static bool create_run_template(struct lxc_container *c, char *tpath, bool quiet
> * If we're running the template in a mapped userns, then
> * we prepend the template command with:
> * lxc-usernsexec <-m map1> ... <-m mapn> --
> + * and we append "--mapped-uid x", where x is the mapped uid
> + * for our geteuid()
> */
> if (geteuid() != 0 && !lxc_list_empty(&conf->id_map)) {
> int n2args = 1;
> + char txtuid[20];
> char **n2 = malloc(n2args * sizeof(*n2));
> struct lxc_list *it;
> struct id_map *map;
>
> + if (!n2) {
> + SYSERROR("out of memory");
> + exit(1);
> + }
> newargv[0] = tpath;
> tpath = "lxc-usernsexec";
> n2[0] = "lxc-usernsexec";
> lxc_list_for_each(it, &conf->id_map) {
> map = it->elem;
> n2args += 2;
> - n2 = realloc(n2, n2args * sizeof(*n2));
> + n2 = realloc(n2, n2args * sizeof(char *));
> +INFO("allocated %d items to n2", n2args);
^ what happened with indentation here?
> if (!n2)
> exit(1);
> n2[n2args-2] = "-m";
> @@ -942,15 +950,15 @@ static bool create_run_template(struct lxc_container *c, char *tpath, bool quiet
> if (ret < 0 || ret >= 200)
> exit(1);
> }
> - bool hostid_mapped = hostid_is_mapped(geteuid(), conf);
> - int extraargs = hostid_mapped ? 1 : 3;
> - n2 = realloc(n2, (nargs + n2args + extraargs) * sizeof(*n2));
> + int hostid_mapped = mapped_hostid(geteuid(), conf);
> + int extraargs = hostid_mapped >= 0 ? 1 : 3;
> + n2 = realloc(n2, (nargs + n2args + extraargs) * sizeof(char *));
> if (!n2)
> exit(1);
> - if (!hostid_mapped) {
> - int free_id = find_unmapped_nsuid(conf);
> + if (hostid_mapped < 0) {
> + hostid_mapped = find_unmapped_nsuid(conf);
> n2[n2args++] = "-m";
> - if (free_id < 0) {
> + if (hostid_mapped < 0) {
> ERROR("Could not find free uid to map");
> exit(1);
> }
> @@ -960,7 +968,7 @@ static bool create_run_template(struct lxc_container *c, char *tpath, bool quiet
> exit(1);
> }
> ret = snprintf(n2[n2args-1], 200, "u:%d:%d:1",
> - free_id, geteuid());
> + hostid_mapped, geteuid());
> if (ret < 0 || ret >= 200) {
> ERROR("string too long");
> exit(1);
> @@ -969,6 +977,20 @@ static bool create_run_template(struct lxc_container *c, char *tpath, bool quiet
> n2[n2args++] = "--";
> for (i = 0; i < nargs; i++)
> n2[i + n2args] = newargv[i];
> + n2args += nargs;
> + // Finally add "--mapped-uid $uid" to tell template what to chown
> + // cached images to
> + n2args += 2;
> + n2 = realloc(n2, n2args * sizeof(char *));
> + if (!n2) {
> + SYSERROR("out of memory");
> + exit(1);
> + }
> + // note n2[n2args-1] is NULL
> + n2[n2args-3] = "--mapped-uid";
> + snprintf(txtuid, 20, "%d", hostid_mapped);
> + n2[n2args-2] = txtuid;
> + n2[n2args-1] = NULL;
> free(newargv);
> newargv = n2;
> }
> diff --git a/templates/lxc-ubuntu-cloud.in b/templates/lxc-ubuntu-cloud.in
> index 82a7f74..41f1c70 100644
> --- a/templates/lxc-ubuntu-cloud.in
> +++ b/templates/lxc-ubuntu-cloud.in
> @@ -80,7 +80,11 @@ lxc.cap.drop = sys_module mac_admin mac_override sys_time
> #lxc.hook.mount = /usr/share/lxc/hooks/mountcgroups
>
> lxc.hook.clone = ${CLONE_HOOK_FN}
> +EOF
>
> + # can't write to devices.deny without CAP_SYS_ADMIN in init-user-ns
> + if [ $in_userns -ne 1 ]; then
> + cat <<EOF >> $path/config
> lxc.cgroup.devices.deny = a
> # Allow any mknod (but not using the node)
> lxc.cgroup.devices.allow = c *:* m
> @@ -109,6 +113,7 @@ lxc.cgroup.devices.allow = c 10:228 rwm
> # kvm
> lxc.cgroup.devices.allow = c 10:232 rwm
> EOF
> + fi
>
> cat <<EOF > $path/fstab
> proc proc proc nodev,noexec,nosuid 0 0
> @@ -123,6 +128,7 @@ EOF
> # that in the kernel, but not right now. So let's just bind
> # mount the files from the host.
> if [ $in_userns -eq 1 ]; then
> + mkdir -p $rootfs/dev/pts
> for dev in null tty urandom console; do
> touch $rootfs/dev/$dev
> echo "/dev/$dev dev/$dev none bind 0 0" >> $path/fstab
> @@ -161,13 +167,14 @@ EOF
> return 0
> }
>
> -options=$(getopt -o a:hp:r:n:Fi:CLS:T:ds:u: -l arch:,help,rootfs:,path:,release:,name:,flush-cache,hostid:,auth-key:,cloud,no_locales,tarball:,debug,stream:,userdata: -- "$@")
> +options=$(getopt -o a:hp:r:n:Fi:CLS:T:ds:u: -l arch:,help,rootfs:,path:,release:,name:,flush-cache,hostid:,auth-key:,cloud,no_locales,tarball:,debug,stream:,userdata:,mapped-uid: -- "$@")
> if [ $? -ne 0 ]; then
> usage $(basename $0)
> exit 1
> fi
> eval set -- "$options"
>
> +mapped_uid=-1
> # default release is precise, or the systems release if recognized
> release=precise
> if [ -f /etc/lsb-release ]; then
> @@ -224,11 +231,13 @@ do
> -u|--userdata) cloneargs[${#cloneargs[@]}]="--userdata=$2"; shift 2;;
> -C|--cloud) cloneargs[${#cloneargs[@]}]="--cloud"; shift 1;;
> -S|--auth-key) cloneargs[${#cloneargs[@]}]="--auth-key=$2"; shift 2;;
> + --mapped-uid) mapped_uid=$2; shift 2;;
> --) shift 1; break ;;
> *) break ;;
> esac
> done
>
> +echo "mapped_uid is .$mapped_uid."
> cloneargs=( "--name=$name" "${cloneargs[@]}" )
>
> if [ $debug -eq 1 ]; then
> @@ -296,6 +305,8 @@ type wget
> # determine the url, tarball, and directory names
> # download if needed
> cache="$STATE_DIR/cache/lxc/cloud-$release"
> +STATE_DIR="$HOME/.cache/lxc/"
> +cache="$HOME/.cache/lxc/cloud-$release"
>
> mkdir -p $cache
>
> @@ -371,7 +382,11 @@ do_extract_rootfs() {
> echo "Extracting container rootfs"
> mkdir -p $rootfs
> cd $rootfs
> - tar --numeric-owner -xpzf "$cache/$filename"
> + if [ $in_userns -eq 1 ]; then
> + tar --anchored --exclude="dev/*" --numeric-owner -xpzf "$cache/$filename"
> + else
> + tar --numeric-owner -xpzf "$cache/$filename"
> + fi
> }
>
> if [ -n "$tarball" ]; then
> @@ -388,6 +403,12 @@ copy_configuration $path $rootfs $name $arch $release
>
> "$CLONE_HOOK_FN" "${cloneargs[@]}" "$rootfs"
>
> +if [ $mapped_uid -ne -1 ]; then
> + chown $mapped_uid $path/config
> + chown -R $mapped_uid $STATE_DIR
> + chown -R $mapped_uid $cache
> +fi
> +
> echo "Container $name created."
> exit 0
>
> --
> 1.8.4.2
>
>
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--
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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