internal/app: less strict username regex

Use the default value of NAME_REGEX from adduser. Should not hurt compatibility while being less strict.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/process_linux.go

@@ -44,7 +44,7 @@ func (seal *outcome) Run(rs *RunState) error {
 	defer func() {
 		var revertErr error
 		storeErr := new(StateStoreError)
-		storeErr.Inner, storeErr.DoErr = store.Do(seal.user.aid.unwrap(), func(c state.Cursor) {
+		storeErr.Inner, storeErr.DoErr = store.Do(seal.user.identity.unwrap(), func(c state.Cursor) {
 			revertErr = func() error {
 				storeErr.InnerErr = deferredStoreFunc(c)
 
@@ -102,7 +102,7 @@ func (seal *outcome) Run(rs *RunState) error {
 			// passed through to shim by hsu
 			shimEnv + "=" + strconv.Itoa(fd),
 			// interpreted by hsu
-			"HAKUREI_APP_ID=" + seal.user.aid.String(),
+			"HAKUREI_APP_ID=" + seal.user.identity.String(),
 		}
 	}
 
@@ -155,7 +155,7 @@ func (seal *outcome) Run(rs *RunState) error {
 			PID:  cmd.Process.Pid,
 			Time: *rs.Time,
 		}
-		earlyStoreErr.Inner, earlyStoreErr.DoErr = store.Do(seal.user.aid.unwrap(), func(c state.Cursor) {
+		earlyStoreErr.Inner, earlyStoreErr.DoErr = store.Do(seal.user.identity.unwrap(), func(c state.Cursor) {
 			earlyStoreErr.InnerErr = c.Save(&sd, seal.ct)
 		})
 	}

internal/app/seal_linux.go

@@ -10,7 +10,6 @@ import (
 	"io/fs"
 	"os"
 	"path"
-	"regexp"
 	"slices"
 	"strconv"
 	"strings"
@@ -59,8 +58,6 @@ var (
 	ErrPulseMode   = errors.New("unexpected pulse socket mode")
 )
 
-var posixUsername = regexp.MustCompilePOSIX("^[a-z_]([A-Za-z0-9_-]{0,31}|[A-Za-z0-9_-]{0,30}\\$)$")
-
 // outcome stores copies of various parts of [hst.Config]
 type outcome struct {
 	// copied from initialising [app]
@@ -135,8 +132,7 @@ func (share *shareHost) runtime() *container.Absolute {
 
 // hsuUser stores post-hsu credentials and metadata
 type hsuUser struct {
-	// identity
-	aid *stringPair[int]
+	identity *stringPair[int]
 	// target uid resolved by hid:aid
 	uid *stringPair[int]
 
@@ -172,25 +168,24 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		seal.ct = ct
 	}
 
-	// allowed aid range 0 to 9999, this is checked again in hsu
+	// allowed identity range 0 to 9999, this is checked again in hsu
 	if config.Identity < 0 || config.Identity > 9999 {
 		return hlog.WrapErr(ErrIdent,
 			fmt.Sprintf("identity %d out of range", config.Identity))
 	}
 
 	seal.user = hsuUser{
-		aid:      newInt(config.Identity),
+		identity: newInt(config.Identity),
 		home:     config.Home,
 		username: config.Username,
 	}
 	if seal.user.username == "" {
 		seal.user.username = "chronos"
-	} else if !posixUsername.MatchString(seal.user.username) ||
-		len(seal.user.username) >= sysconf(_SC_LOGIN_NAME_MAX) {
+	} else if !isValidUsername(seal.user.username) {
 		return hlog.WrapErr(ErrName,
 			fmt.Sprintf("invalid user name %q", seal.user.username))
 	}
-	if u, err := sys.Uid(seal.user.aid.unwrap()); err != nil {
+	if u, err := sys.Uid(seal.user.identity.unwrap()); err != nil {
 		return err
 	} else {
 		seal.user.uid = newInt(u)
@@ -318,7 +313,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		runtimeDir := share.sc.SharePath.Append("runtime")
 		seal.sys.Ensure(runtimeDir.String(), 0700)
 		seal.sys.UpdatePermType(system.User, runtimeDir.String(), acl.Execute)
-		runtimeDirInst := runtimeDir.Append(seal.user.aid.String())
+		runtimeDirInst := runtimeDir.Append(seal.user.identity.String())
 		seal.sys.Ensure(runtimeDirInst.String(), 0700)
 		seal.sys.UpdatePermType(system.User, runtimeDirInst.String(), acl.Read, acl.Write, acl.Execute)
 		seal.container.Tmpfs(container.AbsFHSRunUser, 1<<12, 0755)
@@ -329,7 +324,7 @@ func (seal *outcome) finalise(ctx context.Context, sys sys.State, config *hst.Co
 		tmpdir := share.sc.SharePath.Append("tmpdir")
 		seal.sys.Ensure(tmpdir.String(), 0700)
 		seal.sys.UpdatePermType(system.User, tmpdir.String(), acl.Execute)
-		tmpdirInst := tmpdir.Append(seal.user.aid.String())
+		tmpdirInst := tmpdir.Append(seal.user.identity.String())
 		seal.sys.Ensure(tmpdirInst.String(), 01700)
 		seal.sys.UpdatePermType(system.User, tmpdirInst.String(), acl.Read, acl.Write, acl.Execute)
 		// mount inner /tmp from share so it shares persistence and storage behaviour of host /tmp

internal/app/username.go

@@ -0,0 +1,12 @@
+package app
+
+import "regexp"
+
+// nameRegex is the default NAME_REGEX value from adduser.
+var nameRegex = regexp.MustCompilePOSIX(`^[a-zA-Z][a-zA-Z0-9_-]*\$?$`)
+
+// isValidUsername returns whether the argument is a valid username
+func isValidUsername(username string) bool {
+	return len(username) < sysconf(_SC_LOGIN_NAME_MAX) &&
+		nameRegex.MatchString(username)
+}