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Set file permissions of code directory when layer present #27

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Oct 24, 2023
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17 changes: 17 additions & 0 deletions cmd/localstack/file_utils.go
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package main

import (
"io"
"os"
"path/filepath"
)
Expand All @@ -20,3 +21,19 @@ func ChmodRecursively(root string, mode os.FileMode) error {
return nil
})
}

// Check if a directory is empty
// Source: https://stackoverflow.com/questions/30697324/how-to-check-if-directory-on-path-is-empty/30708914#30708914
func IsDirEmpty(name string) (bool, error) {
f, err := os.Open(name)
if err != nil {
return false, err
}
defer f.Close()

_, err = f.Readdirnames(1) // faster than f.Readdir(1)
if err == io.EOF {
return true, nil
}
return false, err // Either not empty or error, suits both cases
}
17 changes: 13 additions & 4 deletions cmd/localstack/main.go
Original file line number Diff line number Diff line change
Expand Up @@ -132,13 +132,22 @@ func main() {
log.Fatal("Failed to download code archives: " + err.Error())
}

// fix permissions of the layers directory for better AWS parity
// set file permissions of the tmp directory for better AWS parity
if err := ChmodRecursively("/tmp", 0700); err != nil {
log.Warnln("Could not change file mode recursively of directory /tmp:", err)
}
// set file permissions of the layers directory for better AWS parity
if err := ChmodRecursively("/opt", 0755); err != nil {
log.Warnln("Could not change file mode recursively of directory /opt:", err)
}
// fix permissions of the tmp directory for better AWS parity
if err := ChmodRecursively("/tmp", 0700); err != nil {
log.Warnln("Could not change file mode recursively of directory /tmp:", err)
// set file permissions of the code directory if at least one layer is present for better AWS parity
// Limitation: hot reloading likely breaks file permission parity for /var/task in combination with layers
// Heuristic for detecting the presence of layers. It might fail for an empty layer or image-based Lambda.
if isDirEmpty, _ := IsDirEmpty("/opt"); !isDirEmpty {
log.Debugln("Detected layer present")
if err := ChmodRecursively("/var/task", 0755); err != nil {
log.Warnln("Could not change file mode recursively of directory /var/task:", err)
}
}

// parse CLI args
Expand Down