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hack(util): ignore uid/gid chances for envbuilder binary in CacheHasher() #19

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Merged
merged 3 commits into from
Aug 3, 2024
Merged

hack(util): ignore uid/gid chances for envbuilder binary in CacheHasher() #19

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hack(util): ignore uid/gid chances for envbuilder binary in CacheHash…
johnstcn Aug 2, 2024
3854ea6
also handle magic image file
johnstcn Aug 2, 2024
d6a78b0
.envbuilder.tmp
johnstcn Aug 3, 2024
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27 changes: 24 additions & 3 deletions pkg/util/util.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,9 +22,12 @@ import (
"encoding/hex"
"fmt"
"io"
"log"
"math"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"syscall"
"time"
Expand Down Expand Up @@ -95,9 +98,27 @@ func CacheHasher() func(string) (string, error) {
}
h.Write([]byte(fi.Mode().String()))

h.Write([]byte(strconv.FormatUint(uint64(fi.Sys().(*syscall.Stat_t).Uid), 36)))
h.Write([]byte(","))
h.Write([]byte(strconv.FormatUint(uint64(fi.Sys().(*syscall.Stat_t).Gid), 36)))
// Cian: this is a disgusting hack, but it removes the need for the
// envbuilder binary to be owned by root when doing a cache probe.
// We want to ignore UID and GID changes for the envbuilder binary
// specifically. When building and pushing an image using the envbuilder
// image, the embedded envbuilder binary will most likely be owned by
// root:root. However, when performing a cache probe operation, it is more
// likely that the file will be owned by the UID/GID that is running
// envbuilder, which in this case is not guaranteed to be root.
// Let's just pretend that it is, cross our fingers, and hope for the best.
lyingAboutOwnership := !fi.IsDir() &&
strings.HasSuffix(filepath.Clean(filepath.Dir(p)), ".envbuilder.tmp")
if lyingAboutOwnership {
log.Printf("CacheHasher lying about ownership of path %q\n", p)
h.Write([]byte(strconv.FormatUint(uint64(0), 36)))
h.Write([]byte(","))
h.Write([]byte(strconv.FormatUint(uint64(0), 36)))
} else {
h.Write([]byte(strconv.FormatUint(uint64(fi.Sys().(*syscall.Stat_t).Uid), 36)))
h.Write([]byte(","))
h.Write([]byte(strconv.FormatUint(uint64(fi.Sys().(*syscall.Stat_t).Gid), 36)))
}

if fi.Mode().IsRegular() {
f, err := os.Open(p)
Expand Down
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