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[Auditbeat] btmp offset check #24515

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Mar 15, 2021
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[Auditbeat] btmp offset check #24515

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0a21f8e
auditbeat btmp offset check
leehinman Mar 11, 2021
1c9370f
Add additional checks
leehinman Mar 15, 2021
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1 change: 1 addition & 0 deletions CHANGELOG.next.asciidoc
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Expand Up @@ -262,6 +262,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
- system/socket: Having some CPUs unavailable to Auditbeat could cause startup errors or event loss. {pull}22827[22827]
- Note incompatibility of system/socket on ARM. {pull}23381[23381]
- system/login: Fixed offset reset on inode reuse. {pull}24414[24414]
- system/login: Add additional offset check for utmp files. {pull}24515[24515]

*Filebeat*

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6 changes: 3 additions & 3 deletions x-pack/auditbeat/module/system/login/utmp.go
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Expand Up @@ -181,14 +181,14 @@ func (r *UtmpFileReader) readNewInFile(loginRecordC chan<- LoginRecord, errorC c

size := utmpFile.Size
oldSize := savedUtmpFile.Size
if size < oldSize {
if size < oldSize || utmpFile.Offset > size {
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not sure, but maybe we need to add this check to line 233 also

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I think you are correct, I added 2 more checks,

// UTMP files are append-only and so this is weird. It might be a sign of
// a highly unlikely inode reuse - or of something more nefarious.
// Setting isKnownFile to false so we read the whole file from the beginning.
isKnownFile = false

r.log.Warnf("Unexpectedly, the file %v is smaller than before (new: %v, old: %v) - reading whole file.",
utmpFile.Path, size, oldSize)
r.log.Warnf("saved size or offset illogical (new=%+v, saved=%+v) - reading whole file.",
utmpFile, savedUtmpFile)
}

if !isKnownFile && size == 0 {
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