system: isolate app/system into generic implementation

This improves maintainability and extensibility of system operations, makes writing tests for them possible, and operations now apply and revert in order, instead of being bunched up into their own categories.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

1 files changed, 141 insertions, 0 deletions

diff --git a/internal/system/tmpfiles.go b/internal/system/tmpfiles.go
new file mode 100644
index 00000000..2a9f724a
--- /dev/null
+++ b/internal/system/tmpfiles.go
@@ -0,0 +1,141 @@
+package system
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+
+	"git.ophivana.moe/cat/fortify/acl"
+	"git.ophivana.moe/cat/fortify/internal/fmsg"
+	"git.ophivana.moe/cat/fortify/internal/state"
+	"git.ophivana.moe/cat/fortify/internal/verbose"
+)
+
+// CopyFile registers an Op that copies path dst from src.
+func (sys *I) CopyFile(dst, src string) {
+	sys.CopyFileType(Process, dst, src)
+}
+
+// CopyFileType registers a file copying Op labelled with type et.
+func (sys *I) CopyFileType(et state.Enablement, dst, src string) {
+	sys.lock.Lock()
+	sys.ops = append(sys.ops, &Tmpfile{et, tmpfileCopy, dst, src})
+	sys.lock.Unlock()
+
+	sys.UpdatePermType(et, dst, acl.Read)
+}
+
+// Link registers an Op that links dst to src.
+func (sys *I) Link(oldname, newname string) {
+	sys.LinkFileType(Process, oldname, newname)
+}
+
+// LinkFileType registers a file linking Op labelled with type et.
+func (sys *I) LinkFileType(et state.Enablement, oldname, newname string) {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &Tmpfile{et, tmpfileLink, newname, oldname})
+}
+
+// Write registers an Op that writes dst with the contents of src.
+func (sys *I) Write(dst, src string) {
+	sys.WriteType(Process, dst, src)
+}
+
+// WriteType registers a file writing Op labelled with type et.
+func (sys *I) WriteType(et state.Enablement, dst, src string) {
+	sys.lock.Lock()
+	sys.ops = append(sys.ops, &Tmpfile{et, tmpfileWrite, dst, src})
+	sys.lock.Unlock()
+
+	sys.UpdatePermType(et, dst, acl.Read)
+}
+
+const (
+	tmpfileCopy uint8 = iota
+	tmpfileLink
+	tmpfileWrite
+)
+
+type Tmpfile struct {
+	et       state.Enablement
+	method   uint8
+	dst, src string
+}
+
+func (t *Tmpfile) Type() state.Enablement {
+	return t.et
+}
+
+func (t *Tmpfile) apply(_ *I) error {
+	switch t.method {
+	case tmpfileCopy:
+		verbose.Printf("publishing tmpfile %s\n", t)
+		return fmsg.WrapErrorSuffix(copyFile(t.dst, t.src),
+			fmt.Sprintf("cannot copy tmpfile %q:", t.dst))
+	case tmpfileLink:
+		verbose.Printf("linking tmpfile %s\n", t)
+		return fmsg.WrapErrorSuffix(os.Link(t.src, t.dst),
+			fmt.Sprintf("cannot link tmpfile %q:", t.dst))
+	case tmpfileWrite:
+		verbose.Printf("writing %s\n", t)
+		return fmsg.WrapErrorSuffix(os.WriteFile(t.dst, []byte(t.src), 0600),
+			fmt.Sprintf("cannot write tmpfile %q:", t.dst))
+	default:
+		panic("invalid tmpfile method " + strconv.Itoa(int(t.method)))
+	}
+}
+
+func (t *Tmpfile) revert(_ *I, ec *Criteria) error {
+	if ec.hasType(t) {
+		verbose.Printf("removing tmpfile %q\n", t.dst)
+		return fmsg.WrapErrorSuffix(os.Remove(t.dst),
+			fmt.Sprintf("cannot remove tmpfile %q:", t.dst))
+	} else {
+		verbose.Printf("skipping tmpfile %q\n", t.dst)
+		return nil
+	}
+}
+
+func (t *Tmpfile) Is(o Op) bool {
+	t0, ok := o.(*Tmpfile)
+	return ok && t0 != nil && *t == *t0
+}
+
+func (t *Tmpfile) Path() string {
+	if t.method == tmpfileWrite {
+		return fmt.Sprintf("(%d bytes of data)", len(t.src))
+	}
+	return t.src
+}
+
+func (t *Tmpfile) String() string {
+	switch t.method {
+	case tmpfileCopy:
+		return fmt.Sprintf("%q from %q", t.dst, t.src)
+	case tmpfileLink:
+		return fmt.Sprintf("%q from %q", t.dst, t.src)
+	case tmpfileWrite:
+		return fmt.Sprintf("%d bytes of data to %q", len(t.src), t.dst)
+	default:
+		panic("invalid tmpfile method " + strconv.Itoa(int(t.method)))
+	}
+}
+
+func copyFile(dst, src string) error {
+	dstD, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+
+	srcD, err := os.Open(src)
+	if err != nil {
+		return errors.Join(err, dstD.Close())
+	}
+
+	_, err = io.Copy(dstD, srcD)
+	return errors.Join(err, dstD.Close(), srcD.Close())
+}