system: separate link Op implementation

This Op would still be useful after replacing the Tmpfiles interface, so isolate it here.

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

1 files changed, 53 insertions, 0 deletions

diff --git a/internal/system/link.go b/internal/system/link.go
new file mode 100644
index 00000000..cbde3a1f
--- /dev/null
+++ b/internal/system/link.go
@@ -0,0 +1,53 @@
+package system
+
+import (
+	"fmt"
+	"os"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// Link registers an Op that links dst to src.
+func (sys *I) Link(oldname, newname string) *I { return sys.LinkFileType(Process, oldname, newname) }
+
+// LinkFileType registers a file linking Op labelled with type et.
+func (sys *I) LinkFileType(et Enablement, oldname, newname string) *I {
+	sys.lock.Lock()
+	defer sys.lock.Unlock()
+
+	sys.ops = append(sys.ops, &Hardlink{et, newname, oldname})
+
+	return sys
+}
+
+type Hardlink struct {
+	et       Enablement
+	dst, src string
+}
+
+func (l *Hardlink) Type() Enablement { return l.et }
+
+func (l *Hardlink) apply(_ *I) error {
+	fmsg.VPrintln("linking ", l)
+	return fmsg.WrapErrorSuffix(os.Link(l.src, l.dst),
+		fmt.Sprintf("cannot link %q:", l.dst))
+}
+
+func (l *Hardlink) revert(_ *I, ec *Criteria) error {
+	if ec.hasType(l) {
+		fmsg.VPrintf("removing hard link %q", l.dst)
+		return fmsg.WrapErrorSuffix(os.Remove(l.dst),
+			fmt.Sprintf("cannot remove hard link %q:", l.dst))
+	} else {
+		fmsg.VPrintf("skipping hard link %q", l.dst)
+		return nil
+	}
+}
+
+func (l *Hardlink) Is(o Op) bool {
+	l0, ok := o.(*Hardlink)
+	return ok && l0 != nil && *l == *l0
+}
+
+func (l *Hardlink) Path() string   { return l.src }
+func (l *Hardlink) String() string { return fmt.Sprintf("%q from %q", l.dst, l.src) }