Use proto structs for seccheck points

Given that in most cases points are serialized to another process,
point data is now created diretly into protos.

As part of this change, infrastructure to track optional and context
fields was created to facilitate addition of lots of Points which is
needed for upcomming of changes.

Updates #4805

Currently the SST code is converting seccheck protos into SST protos
in the sentry before sending it to the API. After this change, SST
checker will be changed to send seccheck protos to the API and the
API then converts these into SST on the way to pubsub.

PiperOrigin-RevId: 442688320

pkg/sentry/kernel/auth/BUILD

@@ -65,6 +65,8 @@ go_library(
         "//pkg/context",
         "//pkg/errors/linuxerr",
         "//pkg/log",
+        "//pkg/sentry/seccheck",
+        "//pkg/sentry/seccheck/points:points_go_proto",
         "//pkg/sync",
     ],
 )

pkg/sentry/kernel/auth/credentials.go

@@ -17,6 +17,8 @@ package auth
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/sentry/seccheck"
+	pb "gvisor.dev/gvisor/pkg/sentry/seccheck/points/points_go_proto"
 )
 
 // Credentials contains information required to authorize privileged operations
@@ -260,3 +262,17 @@ func (c *Credentials) SetGID(gid GID) error {
 	c.SavedKGID = kgid
 	return nil
 }
+
+// LoadSeccheckData sets credential data based on mask.
+func (c *Credentials) LoadSeccheckData(mask seccheck.FieldMask, info *pb.ContextData) {
+	if mask.Contains(seccheck.FieldCtxtCredentials) {
+		info.Credentials = &pb.Credentials{
+			RealUid:      uint32(c.RealKUID),
+			EffectiveUid: uint32(c.EffectiveKUID),
+			SavedUid:     uint32(c.SavedKUID),
+			RealGid:      uint32(c.RealKGID),
+			EffectiveGid: uint32(c.EffectiveKGID),
+			SavedGid:     uint32(c.SavedKGID),
+		}
+	}
+}