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Writer: ensure ModTime is at least Unix epoch #15

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Merged
chrisnovakovic merged 1 commit into from
Oct 8, 2025
Merged

Writer: ensure ModTime is at least Unix epoch #15

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9 changes: 9 additions & 0 deletions writer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,10 +6,14 @@ import (
"fmt"
"io"
"strconv"
"time"
)

var (
ErrWriteTooLong = errors.New("ar: write too long")

// Epoch is the Unix epoch, 00:00:00 UTC on 1970-01-01.
Epoch = time.Unix(0, 0)
)

// Writer provides sequential writing of an ar archive.
Expand Down Expand Up @@ -228,6 +232,11 @@ func (aw *Writer) WriteHeader(hdr *Header) error {
// This should be unreachable.
return errors.New("ar: unsupported variant")
}
// Modification times before the Unix epoch cannot meaningfully be represented in ar headers, which
// store times as stringified Unix times - ensure the modification time is at least the epoch.
if hdr.ModTime.Before(Epoch) {
hdr.ModTime = Epoch
}
aw.numeric(s.next(12), hdr.ModTime.Unix())
aw.numeric(s.next(6), int64(hdr.Uid))
aw.numeric(s.next(6), int64(hdr.Gid))
Expand Down