Execution with Unnecessary Privileges using syscall Package
The Golang function Setuid() is used to set the user ID of the current process. Passing a user ID of 0 to Setuid() changes the process’s user to the root user (superuser). This can lead to privilege escalation, allowing the current process to execute with root-level permissions, which could be exploited by malicious actors to gain control over the system.
Processes running with elevated privileges (such as root) can pose significant security risks if misused. For instance, a vulnerability in such a process could be leveraged by attackers to compromise the entire system. Therefore, it is essential to avoid changing the process’s user ID to 0 unless absolutely necessary and to ensure such usage is thoroughly reviewed and justified.
Examples
package main
import (
"fmt"
"log"
"os"
"syscall"
)
func main() {
if err := syscall.Setuid(0); err != nil {
log.Fatalf("Failed to set UID: %v", err)
}
fmt.Printf("Running as UID: %d\n", os.Getuid())
}
Remediation
- Avoid using Setuid(0) unless absolutely necessary: Review whether running as the root user is required for the task at hand. It is safer to operate with the least privileges necessary.
- Drop privileges as soon as possible: If elevated privileges are required temporarily, ensure that the process drops those privileges immediately after performing the necessary tasks.
- Validate input to avoid malicious manipulation: If input parameters control the user ID passed to Setuid(), ensure they are securely validated and not influenced by untrusted sources.
- Use alternatives to running as root: If feasible, design your application to avoid needing root privileges entirely. Consider utilizing a dedicated service or capability that performs the task in a secure, controlled manner.
package main
import (
"fmt"
"log"
"os"
"syscall"
)
func main() {
if err := syscall.Setuid(500); err != nil {
log.Fatalf("Failed to set UID: %v", err)
}
fmt.Printf("Running as UID: %d\n", os.Getuid())
}
False Positives
In the case of a false positive the rule can be suppressed. Simply add a
trailing or preceding comment line with either the rule ID (GO004) or
rule category name (unnecessary_privileges).
- Using rule ID
- Using category name
package main
import (
"fmt"
"log"
"os"
"syscall"
)
func main() {
// suppress: GO004
if err := syscall.Setuid(500); err != nil {
log.Fatalf("Failed to set UID: %v", err)
}
fmt.Printf("Running as UID: %d\n", os.Getuid())
}
package main
import (
"fmt"
"log"
"os"
"syscall"
)
func main() {
// suppress: unnecessary_privileges
if err := syscall.Setuid(500); err != nil {
log.Fatalf("Failed to set UID: %v", err)
}
fmt.Printf("Running as UID: %d\n", os.Getuid())
}