[libvirt] [RFC PATCH 2/6] LXC: introduce virLXCControllerSetupUserns and lxcContainerSetUserns

[Gao feng]

On 2013/03/11 14:26, Gao feng wrote:
> This patch introduces new helper function
> virLXCControllerSetupUserns, in this function,
> we set the files uid_map and gid_map of process
> libvirt_lxc.
> 

Oops,not libvirt_lxc, it's the init task of container.

> lxcContainerSetUserns is used for creating cred for
> tasks running in container. Since after setuid/setgid,
> we may be a new user. This patch calls lxcContainerSetUserns
> at first to make sure the new created files belong to
> right user.
> 
> Signed-off-by: Gao feng <gaofeng at cn.fujitsu.com>
> ---
>  src/lxc/lxc_container.c  | 55 ++++++++++++++++++++++++++++++----------
>  src/lxc/lxc_controller.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 107 insertions(+), 14 deletions(-)
> 
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index 1d7bc1e..5c66ae3 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -329,6 +329,29 @@ int lxcContainerWaitForContinue(int control)
>  
>  
>  /**
> + * lxcContainerSetUserns:
> + *
> + * This function calls setuid and setgid to create proper
> + * cred for tasks running in container.
> + *
> + * Returns 0 on success or -1 in case of error
> + */
> +static int lxcContainerSetUserns(virDomainDefPtr def)
> +{
> +    if (def->os.userns != VIR_DOMAIN_USER_NS_ENABLED)
> +        return 0;
> +
> +    if (virSetUIDGID(def->os.uidmap.first,
> +                     def->os.gidmap.first) < 0) {
> +        virReportSystemError(errno, "%s",
> +                             _("setuid or setgid failed"));
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +/**
>   * lxcContainerRenameAndEnableInterfaces:
>   * @nveths: number of interfaces
>   * @veths: interface names
> @@ -2221,6 +2244,24 @@ static int lxcContainerChild(void *data)
>          }
>      }
>  
> +    if (!virFileExists(vmDef->os.init)) {
> +        virReportSystemError(errno,
> +                    _("cannot find init path '%s' relative to container root"),
> +                    vmDef->os.init);
> +        goto cleanup;
> +    }
> +
> +    /* Wait for interface devices to show up */
> +    if (lxcContainerWaitForContinue(argv->monitor) < 0) {
> +        virReportSystemError(errno, "%s",
> +                             _("Failed to read the container continue message"));
> +        goto cleanup;
> +    }
> +    VIR_DEBUG("Received container continue message");
> +
> +    if (lxcContainerSetUserns(vmDef) < 0)
> +        goto cleanup;
> +
>      VIR_DEBUG("Container TTY path: %s", ttyPath);
>  
>      ttyfd = open(ttyPath, O_RDWR|O_NOCTTY);
> @@ -2236,20 +2277,6 @@ static int lxcContainerChild(void *data)
>                                  argv->securityDriver) < 0)
>          goto cleanup;
>  
> -    if (!virFileExists(vmDef->os.init)) {
> -        virReportSystemError(errno,
> -                    _("cannot find init path '%s' relative to container root"),
> -                    vmDef->os.init);
> -        goto cleanup;
> -    }
> -
> -    /* Wait for interface devices to show up */
> -    if (lxcContainerWaitForContinue(argv->monitor) < 0) {
> -        virReportSystemError(errno, "%s",
> -                             _("Failed to read the container continue message"));
> -        goto cleanup;
> -    }
> -    VIR_DEBUG("Received container continue message");
>  
>      /* rename and enable interfaces */
>      if (lxcContainerRenameAndEnableInterfaces(!!(vmDef->features &
> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
> index 15aa334..f17142f 100644
> --- a/src/lxc/lxc_controller.c
> +++ b/src/lxc/lxc_controller.c
> @@ -1028,6 +1028,69 @@ cleanup2:
>  }
>  
>  
> +/**
> + * virLXCControllerSetupUserns
> + *
> + * Set proc files for user namespace
> + *
> + * Returns 0 on success or -1 in case of error
> + */
> +static int virLXCControllerSetupUserns(virLXCControllerPtr ctrl)
> +{
> +    char *uid_map = NULL;
> +    char *gid_map = NULL;
> +    char *uidmap_value = NULL;
> +    char *gidmap_value = NULL;
> +    int ret = -1;
> +
> +    if (ctrl->def->os.userns != VIR_DOMAIN_USER_NS_ENABLED)
> +        return 0;
> +
> +    if (virAsprintf(&uid_map, "/proc/%d/uid_map", ctrl->initpid) < 0)
> +        goto cleanup;
> +
> +    if (virAsprintf(&gid_map, "/proc/%d/gid_map", ctrl->initpid) < 0)
> +        goto cleanup;
> +
> +    if (virAsprintf(&uidmap_value, "%u %u %u",
> +                    ctrl->def->os.uidmap.first,
> +                    ctrl->def->os.uidmap.low_first,
> +                    ctrl->def->os.uidmap.count) < 0)
> +        goto cleanup;
> +
> +    if (virAsprintf(&gidmap_value, "%u %u %u",
> +                    ctrl->def->os.gidmap.first,
> +                    ctrl->def->os.gidmap.low_first,
> +                    ctrl->def->os.gidmap.count) < 0)
> +        goto cleanup;
> +
> +    if (virFileWriteStr(uid_map, uidmap_value, 0) < 0) {
> +        if (errno == -ENOENT)
> +            virReportSystemError(errno,
> +                                 _("%s doesn't exist, please disable userns"),
> +                                 uid_map);
> +        virReportSystemError(errno, _("unable write to %s"), uid_map);
> +        goto cleanup;
> +    }
> +
> +    if (virFileWriteStr(gid_map, gidmap_value, 0) < 0) {
> +        if (errno == -ENOENT)
> +            virReportSystemError(errno,
> +                                 _("%s doesn't exist, please disable userns"),
> +                                 gid_map);
> +        virReportSystemError(errno, _("unable write to %s"), gid_map);
> +        goto cleanup;
> +    }
> +
> +    ret = 0;
> +cleanup:
> +    VIR_FREE(uidmap_value);
> +    VIR_FREE(gidmap_value);
> +    VIR_FREE(uid_map);
> +    VIR_FREE(gid_map);
> +    return ret;
> +}
> +
>  
>  /**
>   * virLXCControllerMoveInterfaces
> @@ -1454,6 +1517,9 @@ virLXCControllerRun(virLXCControllerPtr ctrl)
>      VIR_FORCE_CLOSE(control[1]);
>      VIR_FORCE_CLOSE(containerhandshake[1]);
>  
> +    if (virLXCControllerSetupUserns(ctrl) < 0)
> +        goto cleanup;
> +
>      if (virLXCControllerMoveInterfaces(ctrl) < 0)
>          goto cleanup;
>  
>