seccomp: allow to filter syscalls by instruction pointer

PiperOrigin-RevId: 293029446

pkg/seccomp/seccomp.go

@@ -219,24 +219,36 @@ func addSyscallArgsCheck(p *bpf.ProgramBuilder, rules []Rule, action linux.BPFAc
 				switch a := arg.(type) {
 				case AllowAny:
 				case AllowValue:
+					dataOffsetLow := seccompDataOffsetArgLow(i)
+					dataOffsetHigh := seccompDataOffsetArgHigh(i)
+					if i == RuleIP {
+						dataOffsetLow = seccompDataOffsetIPLow
+						dataOffsetHigh = seccompDataOffsetIPHigh
+					}
 					high, low := uint32(a>>32), uint32(a)
 					// assert arg_low == low
-					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, seccompDataOffsetArgLow(i))
+					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, dataOffsetLow)
 					p.AddJumpFalseLabel(bpf.Jmp|bpf.Jeq|bpf.K, low, 0, ruleViolationLabel(ruleSetIdx, sysno, ruleidx))
 					// assert arg_high == high
-					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, seccompDataOffsetArgHigh(i))
+					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, dataOffsetHigh)
 					p.AddJumpFalseLabel(bpf.Jmp|bpf.Jeq|bpf.K, high, 0, ruleViolationLabel(ruleSetIdx, sysno, ruleidx))
 					labelled = true
 				case GreaterThan:
+					dataOffsetLow := seccompDataOffsetArgLow(i)
+					dataOffsetHigh := seccompDataOffsetArgHigh(i)
+					if i == RuleIP {
+						dataOffsetLow = seccompDataOffsetIPLow
+						dataOffsetHigh = seccompDataOffsetIPHigh
+					}
 					labelGood := fmt.Sprintf("gt%v", i)
 					high, low := uint32(a>>32), uint32(a)
 					// assert arg_high < high
-					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, seccompDataOffsetArgHigh(i))
+					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, dataOffsetHigh)
 					p.AddJumpFalseLabel(bpf.Jmp|bpf.Jge|bpf.K, high, 0, ruleViolationLabel(ruleSetIdx, sysno, ruleidx))
 					// arg_high > high
 					p.AddJumpFalseLabel(bpf.Jmp|bpf.Jeq|bpf.K, high, 0, ruleLabel(ruleSetIdx, sysno, ruleidx, labelGood))
 					// arg_low < low
-					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, seccompDataOffsetArgLow(i))
+					p.AddStmt(bpf.Ld|bpf.Abs|bpf.W, dataOffsetLow)
 					p.AddJumpFalseLabel(bpf.Jmp|bpf.Jgt|bpf.K, low, 0, ruleViolationLabel(ruleSetIdx, sysno, ruleidx))
 					p.AddLabel(ruleLabel(ruleSetIdx, sysno, ruleidx, labelGood))
 					labelled = true

pkg/seccomp/seccomp_rules.go

@@ -62,7 +62,11 @@ func (a AllowValue) String() (s string) {
 // rule := Rule {
 //       AllowValue(linux.ARCH_GET_FS | linux.ARCH_SET_FS), // arg0
 // }
-type Rule [6]interface{}
+type Rule [7]interface{} // 6 arguments + RIP
+
+// RuleIP indicates what rules in the Rule array have to be applied to
+// instruction pointer.
+const RuleIP = 6
 
 func (r Rule) String() (s string) {
 	if len(r) == 0 {

pkg/seccomp/seccomp_test.go

@@ -388,6 +388,33 @@ func TestBasic(t *testing.T) {
 				},
 			},
 		},
+		{
+			ruleSets: []RuleSet{
+				{
+					Rules: SyscallRules{
+						1: []Rule{
+							{
+								RuleIP: AllowValue(0x7aabbccdd),
+							},
+						},
+					},
+					Action: linux.SECCOMP_RET_ALLOW,
+				},
+			},
+			defaultAction: linux.SECCOMP_RET_TRAP,
+			specs: []spec{
+				{
+					desc: "IP: Syscall instruction pointer allowed",
+					data: seccompData{nr: 1, arch: linux.AUDIT_ARCH_X86_64, args: [6]uint64{}, instructionPointer: 0x7aabbccdd},
+					want: linux.SECCOMP_RET_ALLOW,
+				},
+				{
+					desc: "IP: Syscall instruction pointer disallowed",
+					data: seccompData{nr: 1, arch: linux.AUDIT_ARCH_X86_64, args: [6]uint64{}, instructionPointer: 0x711223344},
+					want: linux.SECCOMP_RET_TRAP,
+				},
+			},
+		},
 	} {
 		instrs, err := BuildProgram(test.ruleSets, test.defaultAction)
 		if err != nil {