fix: Security hardening follow-ups and 0.3.0 changelog by nfebe · Pull Request #145 · flatrun/agent · GitHub
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fix: Security hardening follow-ups and 0.3.0 changelog #145

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Merged
nfebe merged 3 commits into from
Jun 8, 2026
Merged

fix: Security hardening follow-ups and 0.3.0 changelog #145

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9abd3ae
docs: Add 0.3.0 changelog entry
nfebe Jun 8, 2026
2c6a126
fix(security): Chown symlinks themselves during mount ownership
nfebe Jun 8, 2026
fdc03a4
fix(security): Remove modulo bias from generated alphanumeric secrets
nfebe Jun 8, 2026
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23 changes: 23 additions & 0 deletions CHANGELOG.md
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21 changes: 15 additions & 6 deletions internal/api/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ import (
"encoding/json"
"fmt"
"log"
"math/big"
"net/http"
"os"
"os/exec"
Expand Down Expand Up @@ -4115,23 +4116,31 @@ func generateSecretValue(spec TemplateEnvSecret) (string, error) {
if n <= 0 {
n = 32
}
buf := make([]byte, n)
if _, err := cryptoRand.Read(buf); err != nil {
return "", err
}

var value string
switch spec.Encoding {
case "hex":
buf := make([]byte, n)
if _, err := cryptoRand.Read(buf); err != nil {
return "", err
}
value = hex.EncodeToString(buf)
case "alphanumeric":
const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
out := make([]byte, n)
for i, b := range buf {
out[i] = charset[int(b)%len(charset)]
for i := range out {
idx, err := cryptoRand.Int(cryptoRand.Reader, big.NewInt(int64(len(charset))))
if err != nil {
return "", err
}
out[i] = charset[idx.Int64()]
}
value = string(out)
default:
buf := make([]byte, n)
if _, err := cryptoRand.Read(buf); err != nil {
return "", err
}
value = base64.StdEncoding.EncodeToString(buf)
}

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8 changes: 5 additions & 3 deletions internal/docker/discovery.go
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Original file line number Diff line number Diff line change
Expand Up @@ -399,9 +399,9 @@ func (d *Discovery) ApplyMountOwnership(deploymentPath string, mounts []MountOwn
}
}

if info, err := os.Stat(base); err == nil && !info.IsDir() {
if info, err := os.Lstat(base); err == nil && !info.IsDir() {
if m.User != "" {
if err := os.Chown(base, uid, gid); err != nil {
if err := os.Lchown(base, uid, gid); err != nil {
return fmt.Errorf("chown %s: %w", base, err)
}
}
Expand All @@ -426,7 +426,9 @@ func (d *Discovery) ApplyMountOwnership(deploymentPath string, mounts []MountOwn
if walkErr != nil {
return walkErr
}
return os.Chown(path, uid, gid)
// Runs as root over container-written content: following a
// planted symlink would chown an arbitrary host file.
return os.Lchown(path, uid, gid)
})
if err != nil {
return fmt.Errorf("chown %s: %w", base, err)
Expand Down
29 changes: 29 additions & 0 deletions internal/docker/discovery_test.go
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