dotcloud/docker

package dockerfile // import "github.com/docker/docker/builder/dockerfile"

import (
    "context"
    "path/filepath"
    "strconv"
    "strings"

    "github.com/docker/docker/pkg/idtools"
    "github.com/moby/sys/symlink"
    "github.com/moby/sys/user"
    "github.com/pkg/errors"
)

func parseChownFlag(ctx context.Context, builder *Builder, state *dispatchState, chown, ctrRootPath string, identityMapping idtools.IdentityMapping) (idtools.Identity, error) {
    var userStr, grpStr string
    parts := strings.Split(chown, ":")
    if len(parts) > 2 {
        return idtools.Identity{}, errors.New("invalid chown string format: " + chown)
    }
    if len(parts) == 1 {
        // if no group specified, use the user spec as group as well
        userStr, grpStr = parts[0], parts[0]
    } else {
        userStr, grpStr = parts[0], parts[1]
    }

    passwdPath, err := symlink.FollowSymlinkInScope(filepath.Join(ctrRootPath, "etc", "passwd"), ctrRootPath)
    if err != nil {
        return idtools.Identity{}, errors.Wrapf(err, "can't resolve /etc/passwd path in container rootfs")
    }
    groupPath, err := symlink.FollowSymlinkInScope(filepath.Join(ctrRootPath, "etc", "group"), ctrRootPath)
    if err != nil {
        return idtools.Identity{}, errors.Wrapf(err, "can't resolve /etc/group path in container rootfs")
    }
    uid, err := lookupUser(userStr, passwdPath)
    if err != nil {
        return idtools.Identity{}, errors.Wrapf(err, "can't find uid for user "+userStr)
    }
    gid, err := lookupGroup(grpStr, groupPath)
    if err != nil {
        return idtools.Identity{}, errors.Wrapf(err, "can't find gid for group "+grpStr)
    }

    // convert as necessary because of user namespaces
    chownPair, err := identityMapping.ToHost(idtools.Identity{UID: uid, GID: gid})
    if err != nil {
        return idtools.Identity{}, errors.Wrapf(err, "unable to convert uid/gid to host mapping")
    }
    return chownPair, nil
}

func lookupUser(userStr, filepath string) (int, error) {
    // if the string is actually a uid integer, parse to int and return
    // as we don't need to translate with the help of files
    uid, err := strconv.Atoi(userStr)
    if err == nil {
        return uid, nil
    }
    users, err := user.ParsePasswdFileFilter(filepath, func(u user.User) bool {
        return u.Name == userStr
    })
    if err != nil {
        return 0, err
    }
    if len(users) == 0 {
        return 0, errors.New("no such user: " + userStr)
    }
    return users[0].Uid, nil
}

func lookupGroup(groupStr, filepath string) (int, error) {
    // if the string is actually a gid integer, parse to int and return
    // as we don't need to translate with the help of files
    gid, err := strconv.Atoi(groupStr)
    if err == nil {
        return gid, nil
    }
    groups, err := user.ParseGroupFileFilter(filepath, func(g user.Group) bool {
        return g.Name == groupStr
    })
    if err != nil {
        return 0, err
    }
    if len(groups) == 0 {
        return 0, errors.New("no such group: " + groupStr)
    }
    return groups[0].Gid, nil
}