app: extra acl entries from configuration

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

fst/config.go

@@ -35,6 +35,8 @@ type ConfinementConfig struct {
 	Outer string `json:"home"`
 	// bwrap sandbox confinement configuration
 	Sandbox *SandboxConfig `json:"sandbox"`
+	// extra acl entries to append
+	ExtraPerms []*ExtraPermConfig `json:"extra_perms,omitempty"`
 
 	// reference to a system D-Bus proxy configuration,
 	// nil value disables system bus proxy
@@ -78,6 +80,29 @@ type SandboxConfig struct {
 	Override []string `json:"override"`
 }
 
+type ExtraPermConfig struct {
+	Path    string `json:"path"`
+	Read    bool   `json:"r,omitempty"`
+	Write   bool   `json:"w,omitempty"`
+	Execute bool   `json:"x,omitempty"`
+}
+
+func (e *ExtraPermConfig) String() string {
+	buf := make([]byte, 0, 4+len(e.Path))
+	buf = append(buf, '-', '-', '-', ':')
+	buf = append(buf, []byte(e.Path)...)
+	if e.Read {
+		buf[0] = 'r'
+	}
+	if e.Write {
+		buf[1] = 'w'
+	}
+	if e.Execute {
+		buf[2] = 'x'
+	}
+	return string(buf)
+}
+
 type FilesystemConfig struct {
 	// mount point in sandbox, same as src if empty
 	Dst string `json:"dst,omitempty"`

internal/app/seal.go

@@ -8,6 +8,7 @@ import (
 	"regexp"
 	"strconv"
 
+	"git.gensokyo.uk/security/fortify/acl"
 	"git.gensokyo.uk/security/fortify/dbus"
 	"git.gensokyo.uk/security/fortify/fst"
 	"git.gensokyo.uk/security/fortify/internal/fmsg"
@@ -48,6 +49,8 @@ type appSeal struct {
 	et system.Enablements
 	// wayland socket direct access
 	directWayland bool
+	// extra UpdatePerm ops
+	extraPerms []*sealedExtraPerm
 
 	// prevents sharing from happening twice
 	shared bool
@@ -59,6 +62,11 @@ type appSeal struct {
 	// protected by upstream mutex
 }
 
+type sealedExtraPerm struct {
+	name  string
+	perms acl.Perms
+}
+
 // Seal seals the app launch context
 func (a *app) Seal(config *fst.Config) error {
 	a.lock.Lock()
@@ -100,46 +108,66 @@ func (a *app) Seal(config *fst.Config) error {
 	if config.Confinement.AppID < 0 || config.Confinement.AppID > 9999 {
 		return fmsg.WrapError(ErrUser,
 			fmt.Sprintf("aid %d out of range", config.Confinement.AppID))
+	}
+	seal.sys.user = appUser{
+		aid:      config.Confinement.AppID,
+		as:       strconv.Itoa(config.Confinement.AppID),
+		data:     config.Confinement.Outer,
+		home:     config.Confinement.Inner,
+		username: config.Confinement.Username,
+	}
+	if seal.sys.user.username == "" {
+		seal.sys.user.username = "chronos"
+	} else if !posixUsername.MatchString(seal.sys.user.username) {
+		return fmsg.WrapError(ErrName,
+			fmt.Sprintf("invalid user name %q", seal.sys.user.username))
+	}
+	if seal.sys.user.data == "" || !path.IsAbs(seal.sys.user.data) {
+		return fmsg.WrapError(ErrHome,
+			fmt.Sprintf("invalid home directory %q", seal.sys.user.data))
+	}
+	if seal.sys.user.home == "" {
+		seal.sys.user.home = seal.sys.user.data
+	}
+
+	// invoke fsu for full uid
+	if u, err := a.os.Uid(seal.sys.user.aid); err != nil {
+		return fmsg.WrapErrorSuffix(err,
+			"cannot obtain uid from fsu:")
 	} else {
-		seal.sys.user = appUser{
-			aid:      config.Confinement.AppID,
-			as:       strconv.Itoa(config.Confinement.AppID),
-			data:     config.Confinement.Outer,
-			home:     config.Confinement.Inner,
-			username: config.Confinement.Username,
-		}
-		if seal.sys.user.username == "" {
-			seal.sys.user.username = "chronos"
-		} else if !posixUsername.MatchString(seal.sys.user.username) {
-			return fmsg.WrapError(ErrName,
-				fmt.Sprintf("invalid user name %q", seal.sys.user.username))
-		}
-		if seal.sys.user.data == "" || !path.IsAbs(seal.sys.user.data) {
-			return fmsg.WrapError(ErrHome,
-				fmt.Sprintf("invalid home directory %q", seal.sys.user.data))
-		}
-		if seal.sys.user.home == "" {
-			seal.sys.user.home = seal.sys.user.data
-		}
+		seal.sys.user.uid = u
+		seal.sys.user.us = strconv.Itoa(u)
+	}
 
-		// invoke fsu for full uid
-		if u, err := a.os.Uid(seal.sys.user.aid); err != nil {
-			return fmsg.WrapErrorSuffix(err,
-				"cannot obtain uid from fsu:")
+	// resolve supplementary group ids from names
+	seal.sys.user.supp = make([]string, len(config.Confinement.Groups))
+	for i, name := range config.Confinement.Groups {
+		if g, err := a.os.LookupGroup(name); err != nil {
+			return fmsg.WrapError(err,
+				fmt.Sprintf("unknown group %q", name))
 		} else {
-			seal.sys.user.uid = u
-			seal.sys.user.us = strconv.Itoa(u)
+			seal.sys.user.supp[i] = g.Gid
+		}
+	}
+
+	// build extra perms
+	seal.extraPerms = make([]*sealedExtraPerm, len(config.Confinement.ExtraPerms))
+	for i, p := range config.Confinement.ExtraPerms {
+		if p == nil {
+			continue
 		}
 
-		// resolve supplementary group ids from names
-		seal.sys.user.supp = make([]string, len(config.Confinement.Groups))
-		for i, name := range config.Confinement.Groups {
-			if g, err := a.os.LookupGroup(name); err != nil {
-				return fmsg.WrapError(err,
-					fmt.Sprintf("unknown group %q", name))
-			} else {
-				seal.sys.user.supp[i] = g.Gid
-			}
+		seal.extraPerms[i] = new(sealedExtraPerm)
+		seal.extraPerms[i].name = p.Path
+		seal.extraPerms[i].perms = make(acl.Perms, 0, 3)
+		if p.Read {
+			seal.extraPerms[i].perms = append(seal.extraPerms[i].perms, acl.Read)
+		}
+		if p.Write {
+			seal.extraPerms[i].perms = append(seal.extraPerms[i].perms, acl.Write)
+		}
+		if p.Execute {
+			seal.extraPerms[i].perms = append(seal.extraPerms[i].perms, acl.Execute)
 		}
 	}
 

internal/app/share.go

@@ -292,6 +292,14 @@ func (seal *appSeal) setupShares(bus [2]*dbus.Config, os linux.System) error {
 		seal.sys.bwrap.Tmpfs(dest, 8*1024)
 	}
 
+	// append extra perms
+	for _, p := range seal.extraPerms {
+		if p == nil {
+			continue
+		}
+		seal.sys.UpdatePermType(system.User, p.name, p.perms...)
+	}
+
 	return nil
 }
 

print.go

@@ -90,33 +90,47 @@ func printShow(instance *state.State, config *fst.Config, short bool) {
 	fmt.Fprintf(w, " Command:\t%s\n", strings.Join(config.Command, " "))
 	fmt.Fprintf(w, "\n")
 
-	if !short && config.Confinement.Sandbox != nil && len(config.Confinement.Sandbox.Filesystem) > 0 {
-		fmt.Fprintf(w, "Filesystem:\n")
-		for _, f := range config.Confinement.Sandbox.Filesystem {
-			if f == nil {
-				continue
-			}
+	if !short {
+		if config.Confinement.Sandbox != nil && len(config.Confinement.Sandbox.Filesystem) > 0 {
+			fmt.Fprintf(w, "Filesystem\n")
+			for _, f := range config.Confinement.Sandbox.Filesystem {
+				if f == nil {
+					continue
+				}
 
-			expr := new(strings.Builder)
-			if f.Device {
-				expr.WriteString(" d")
-			} else if f.Write {
-				expr.WriteString(" w")
-			} else {
-				expr.WriteString(" ")
+				expr := new(strings.Builder)
+				expr.Grow(3 + len(f.Src) + 1 + len(f.Dst))
+
+				if f.Device {
+					expr.WriteString(" d")
+				} else if f.Write {
+					expr.WriteString(" w")
+				} else {
+					expr.WriteString(" ")
+				}
+				if f.Must {
+					expr.WriteString("*")
+				} else {
+					expr.WriteString("+")
+				}
+				expr.WriteString(f.Src)
+				if f.Dst != "" {
+					expr.WriteString(":" + f.Dst)
+				}
+				fmt.Fprintf(w, "%s\n", expr.String())
 			}
-			if f.Must {
-				expr.WriteString("*")
-			} else {
-				expr.WriteString("+")
-			}
-			expr.WriteString(f.Src)
-			if f.Dst != "" {
-				expr.WriteString(":" + f.Dst)
-			}
-			fmt.Fprintf(w, "%s\n", expr.String())
+			fmt.Fprintf(w, "\n")
+		}
+		if len(config.Confinement.ExtraPerms) > 0 {
+			fmt.Fprintf(w, "Extra ACL\n")
+			for _, p := range config.Confinement.ExtraPerms {
+				if p == nil {
+					continue
+				}
+				fmt.Fprintf(w, " %s\n", p.String())
+			}
+			fmt.Fprintf(w, "\n")
 		}
-		fmt.Fprintf(w, "\n")
 	}
 
 	printDBus := func(c *dbus.Config) {