hst/grp_pwd: specify new uid format

This leaves slots available for additional uid ranges in Rosa OS.

This breaks all existing installations! Users are required to fix ownership manually.

Closes #18.

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

4 files changed, 99 insertions, 6 deletions

diff --git a/hst/config.go b/hst/config.go
index ee31a555..d7078551 100644
--- a/hst/config.go
+++ b/hst/config.go
@@ -59,7 +59,7 @@ func (config *Config) Validate() error {
 	}
 
 	// this is checked again in hsu
-	if config.Identity < IdentityMin || config.Identity > IdentityMax {
+	if config.Identity < IdentityStart || config.Identity > IdentityEnd {
 		return &AppError{Step: "validate configuration", Err: ErrIdentityBounds,
 			Msg: "identity " + strconv.Itoa(config.Identity) + " out of range"}
 	}
diff --git a/hst/container.go b/hst/container.go
index 75643913..f9cc95ed 100644
--- a/hst/container.go
+++ b/hst/container.go
@@ -20,11 +20,6 @@ const (
 	WaitDelayDefault = 5 * time.Second
 	// WaitDelayMax is used if WaitDelay exceeds its value.
 	WaitDelayMax = 30 * time.Second
-
-	// IdentityMin is the minimum value of [Config.Identity]. This is enforced by cmd/hsu.
-	IdentityMin = 0
-	// IdentityMax is the maximum value of [Config.Identity]. This is enforced by cmd/hsu.
-	IdentityMax = 9999
 )
 
 const (
diff --git a/hst/grp_pwd.go b/hst/grp_pwd.go
new file mode 100644
index 00000000..1a5c962e
--- /dev/null
+++ b/hst/grp_pwd.go
@@ -0,0 +1,61 @@
+package hst
+
+import (
+	"fmt"
+	"strconv"
+)
+
+const (
+	// UserOffset is the offset for UID and GID ranges for each user.
+	UserOffset = 100000
+	// RangeSize is the size of each UID and GID range.
+	RangeSize = UserOffset / 10
+
+	// IdentityStart is the first [Config.Identity] value. This is enforced in cmd/hsu.
+	IdentityStart = 0
+	// IdentityEnd is the last [Config.Identity] value. This is enforced in cmd/hsu.
+	IdentityEnd = AppEnd - AppStart
+
+	// AppStart is the first app user UID and GID.
+	AppStart = RangeSize * 1
+	// AppEnd is the last app user UID and GID.
+	AppEnd = AppStart + RangeSize - 1
+
+	/* these are for Rosa OS: use the ranges below to determine whether a process is isolated */
+
+	// IsolatedStart is the start of UID and GID for fully isolated sandboxed processes.
+	IsolatedStart = RangeSize * 9
+	// IsolatedEnd is the end of UID and GID for fully isolated sandboxed processes.
+	IsolatedEnd = IsolatedStart + RangeSize - 1
+)
+
+// A UID represents a kernel uid in the init namespace.
+type UID uint32
+
+// String returns the username corresponding to this uid.
+//
+// Not safe against untrusted input.
+func (uid UID) String() string {
+	appid := uid % UserOffset
+	userid := uid / UserOffset
+	if appid >= IsolatedStart && appid <= IsolatedEnd {
+		return fmt.Sprintf("u%d_i%d", userid, appid-IsolatedStart)
+	} else if appid >= AppStart && appid <= AppEnd {
+		return fmt.Sprintf("u%d_a%d", userid, appid-AppStart)
+	} else {
+		return strconv.Itoa(int(uid))
+	}
+}
+
+// A GID represents a kernel gid in the init namespace.
+type GID uint32
+
+// String returns the group name corresponding to this gid.
+//
+// Not safe against untrusted input.
+func (gid GID) String() string { return UID(gid).String() }
+
+// ToUser returns a [hst.UID] value from userid and appid.
+//
+// Not safe against untrusted input.
+func ToUser[U int | uint32](userid, appid U) U { return userid*UserOffset + AppStart + appid }
diff --git a/hst/grp_pwd_test.go b/hst/grp_pwd_test.go
new file mode 100644
index 00000000..2d01c122
--- /dev/null
+++ b/hst/grp_pwd_test.go
@@ -0,0 +1,37 @@
+package hst_test
+
+import (
+	"strconv"
+	"testing"
+
+	"hakurei.app/hst"
+)
+
+func TestUIDString(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		val  uint32
+		want string
+	}{
+		{hst.AppStart + hst.IdentityStart, "u0_a0"},                           // uidStart
+		{hst.ToUser[uint32](hst.RangeSize-1, hst.IdentityEnd), "u9999_a9999"}, // uidEnd
+
+		{hst.IsolatedStart + hst.IdentityStart, "u0_i0"},                    // isolatedStart
+		{(hst.RangeSize-1)*hst.UserOffset + hst.IsolatedEnd, "u9999_i9999"}, // isolatedEnd
+
+		{0, "0"}, // out of bounds
+	}
+	for _, tc := range testCases {
+		t.Run(strconv.Itoa(int(tc.val)), func(t *testing.T) {
+			t.Parallel()
+
+			if got := hst.UID(tc.val).String(); got != tc.want {
+				t.Fatalf("UID.String: %q, want %q", got, tc.want)
+			}
+			if got := hst.GID(tc.val).String(); got != tc.want {
+				t.Fatalf("GID.String: %q, want %q", got, tc.want)
+			}
+		})
+	}
+}