dit_test.go

     1  // Copyright 2024 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package subtle
     6  
     7  import (
     8  	"internal/cpu"
     9  	"internal/runtime/sys"
    10  	"testing"
    11  )
    12  
    13  func TestWithDataIndependentTiming(t *testing.T) {
    14  	if !cpu.ARM64.HasDIT {
    15  		t.Skip("CPU does not support DIT")
    16  	}
    17  
    18  	ditAlreadyEnabled := sys.DITEnabled()
    19  
    20  	WithDataIndependentTiming(func() {
    21  		if !sys.DITEnabled() {
    22  			t.Fatal("dit not enabled within WithDataIndependentTiming closure")
    23  		}
    24  
    25  		WithDataIndependentTiming(func() {
    26  			if !sys.DITEnabled() {
    27  				t.Fatal("dit not enabled within nested WithDataIndependentTiming closure")
    28  			}
    29  		})
    30  
    31  		if !sys.DITEnabled() {
    32  			t.Fatal("dit not enabled after return from nested WithDataIndependentTiming closure")
    33  		}
    34  	})
    35  
    36  	if !ditAlreadyEnabled && sys.DITEnabled() {
    37  		t.Fatal("dit not unset after returning from WithDataIndependentTiming closure")
    38  	}
    39  }
    40  
    41  func TestDITPanic(t *testing.T) {
    42  	if !cpu.ARM64.HasDIT {
    43  		t.Skip("CPU does not support DIT")
    44  	}
    45  
    46  	ditAlreadyEnabled := sys.DITEnabled()
    47  
    48  	defer func() {
    49  		e := recover()
    50  		if e == nil {
    51  			t.Fatal("didn't panic")
    52  		}
    53  		if !ditAlreadyEnabled && sys.DITEnabled() {
    54  			t.Error("DIT still enabled after panic inside of WithDataIndependentTiming closure")
    55  		}
    56  	}()
    57  
    58  	WithDataIndependentTiming(func() {
    59  		if !sys.DITEnabled() {
    60  			t.Fatal("dit not enabled within WithDataIndependentTiming closure")
    61  		}
    62  
    63  		panic("bad")
    64  	})
    65  }
    66  
    67  func TestDITGoroutineInheritance(t *testing.T) {
    68  	if !cpu.ARM64.HasDIT {
    69  		t.Skip("CPU does not support DIT")
    70  	}
    71  
    72  	ditAlreadyEnabled := sys.DITEnabled()
    73  
    74  	WithDataIndependentTiming(func() {
    75  		done := make(chan struct{})
    76  		go func() {
    77  			if !sys.DITEnabled() {
    78  				t.Error("DIT not enabled in new goroutine")
    79  			}
    80  			close(done)
    81  		}()
    82  		<-done
    83  		if !ditAlreadyEnabled && !sys.DITEnabled() {
    84  			t.Fatal("dit unset after returning from goroutine started in WithDataIndependentTiming closure")
    85  		}
    86  	})
    87  }
    88
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