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Socket dataset: Workaround for bogus dereference in kernel 5.x #15771
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,116 @@ | ||
| // Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one | ||
| // or more contributor license agreements. Licensed under the Elastic License; | ||
| // you may not use this file except in compliance with the Elastic License. | ||
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|
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| // +build linux,386 linux,amd64 | ||
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| package guess | ||
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||
| import ( | ||
| "encoding/hex" | ||
| "os" | ||
| "syscall" | ||
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| "github.com/elastic/beats/libbeat/common" | ||
| "github.com/elastic/beats/x-pack/auditbeat/module/system/socket/helper" | ||
| "github.com/elastic/beats/x-pack/auditbeat/tracing" | ||
| ) | ||
|
|
||
| /* | ||
|
|
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| */ | ||
|
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| func init() { | ||
| if err := Registry.AddGuess(&guessDeref{}); err != nil { | ||
| panic(err) | ||
| } | ||
| } | ||
|
|
||
| const ( | ||
| flagName = "NULL_PTR_DEREF_IS_GARBAGE" | ||
| envVar = "AUDITBEAT_SYSTEM_SOCKET_CHECK_DEREF" | ||
| ) | ||
|
|
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| type guessDeref struct { | ||
| ctx Context | ||
| } | ||
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| func (g *guessDeref) Condition(ctx Context) (bool, error) { | ||
| v := os.Getenv(envVar) | ||
| return v == "1", nil | ||
| } | ||
|
|
||
| // Name of this guess. | ||
| func (g *guessDeref) Name() string { | ||
| return "guess_deref" | ||
| } | ||
|
|
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| // Provides returns the names of discovered variables. | ||
| func (g *guessDeref) Provides() []string { | ||
| return []string{ | ||
| flagName, | ||
| } | ||
| } | ||
|
|
||
| // Requires declares the variables required to run this guess. | ||
| func (g *guessDeref) Requires() []string { | ||
| return []string{ | ||
| "SYS_UNAME", | ||
| } | ||
| } | ||
|
|
||
| // Probes returns a kretprobe on prepare_creds that dumps the first bytes | ||
| // pointed to by the return value, which is a struct cred. | ||
| func (g *guessDeref) Probes() ([]helper.ProbeDef, error) { | ||
| return []helper.ProbeDef{ | ||
| { | ||
| Probe: tracing.Probe{ | ||
| Type: tracing.TypeKProbe, | ||
| Name: "guess_null_ptr_deref", | ||
| Address: "{{.SYS_UNAME}}", | ||
| Fetchargs: helper.MakeMemoryDump("{{.P1}}", 0, credDumpBytes), | ||
| }, | ||
| Decoder: tracing.NewDumpDecoder, | ||
| }, | ||
| }, nil | ||
| } | ||
|
|
||
| // Prepare is a no-op. | ||
| func (g *guessDeref) Prepare(ctx Context) error { | ||
| g.ctx = ctx | ||
| return nil | ||
| } | ||
|
|
||
| // Terminate is a no-op. | ||
| func (g *guessDeref) Terminate() error { | ||
| return nil | ||
| } | ||
|
|
||
| func (g *guessDeref) MaxRepeats() int { | ||
| return 1000 | ||
| } | ||
|
|
||
| // Extract receives the struct cred dump and discovers the offsets. | ||
| func (g *guessDeref) Extract(ev interface{}) (common.MapStr, bool) { | ||
| raw := ev.([]byte) | ||
| if len(raw) != credDumpBytes { | ||
| return nil, false | ||
| } | ||
| for _, val := range raw { | ||
| if val != 0 { | ||
| g.ctx.Log.Errorf("Found non-empty memory:\n%s", hex.Dump(raw)) | ||
| //return nil, false | ||
| } | ||
| } | ||
| return nil, true | ||
| } | ||
|
|
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| // Trigger invokes the SYS_ACCESS syscall: | ||
| // int access(const char *pathname, int mode); | ||
| // The function call will return an error due to path being NULL, but it will | ||
| // have invoked prepare_creds before argument validation. | ||
| func (g *guessDeref) Trigger() error { | ||
| var ptr *syscall.Utsname | ||
| syscall.Uname(ptr) | ||
| return nil | ||
| } | ||
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