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main.go
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main.go
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package main
import (
"context"
"encoding/json"
"fmt"
"io/ioutil"
"log"
"net/http"
"os"
"os/exec"
"strings"
"syscall"
"time"
)
// Maximum allowed code size in bytes
const MaxCodeSize = 1024 * 1024 // 1 MB
// Restricted user and group ID - always 1000 for docker unless explicit
const RestrictedUserID = 1000
const RestrictedGroupID = 1000
type CompileRequest struct {
Code string `json:"code"`
Input string `json:"input"`
Language string `json:"language,omitempty"`
}
func main() {
http.HandleFunc("/compile", handleCompile)
fmt.Println("C++ Server listening on port 8080...")
log.Fatal(http.ListenAndServe(":8080", nil))
}
func handleCompile(w http.ResponseWriter, r *http.Request) {
// Read the request body
body, err := ioutil.ReadAll(r.Body)
if err != nil {
w.WriteHeader(http.StatusBadRequest)
fmt.Fprint(w, "Error occurred during parsing of the request body", err)
log.Printf("Failed to read request body: %v", err)
return
}
// Parse the JSON request body
var compileReq CompileRequest
err = json.Unmarshal(body, &compileReq)
if err != nil {
w.WriteHeader(http.StatusBadRequest)
fmt.Fprint(w, "Error occurred during parsing of the JSON request body", err)
log.Printf("Failed to parse JSON request body: %v", err)
return
}
code := []byte(compileReq.Code)
// Check if the code size exceeds the maximum allowed size
if len(code) > MaxCodeSize {
w.WriteHeader(http.StatusBadRequest)
fmt.Fprintf(w, "Code size too big", err)
log.Printf("Code size exceeds the maximum limit of %d bytes", MaxCodeSize)
return
}
// Create a temporary file to store the code
tmpFile, err := ioutil.TempFile("", "code-*.cpp")
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "Internal server error", err)
log.Printf("Failed to create temporary file: %v", err)
return
}
defer os.Remove(tmpFile.Name()) // Clean up the temporary file
// Write the code to the temporary file
_, err = tmpFile.Write(code)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "Internal server error", err)
log.Printf("Failed to write code to temporary file: %v", err)
return
}
// Close the temporary file
err = tmpFile.Close()
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "Internal server error", err)
log.Printf("Failed to close temporary file: %v", err)
return
}
// Create a temporary file to store the output
tmpOpFile, err := ioutil.TempFile("", "output-*")
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "Internal server error", err)
log.Printf("Failed to create output temporary file: %v\n", err)
return
}
// Compile the code using G++
outputFile := tmpOpFile.Name()
cmd := exec.Command("g++", tmpFile.Name(), "-o", outputFile)
compilerOutput, err := cmd.CombinedOutput()
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "Compilation error: %s", compilerOutput)
log.Printf("Compilation error: %s", err)
return
}
log.Printf("Compilation successful. Output file: %s", outputFile)
// Close the temporary output file
err = tmpOpFile.Close()
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(w, "Internal server error", err)
log.Printf("Failed to close output temporary file: %v", err)
return
}
// Create a context with a timeout duration
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
// Create a channel to receive the output
outputChannel := make(chan []byte)
// Run the compiled output in a Goroutine and monitor for timeouts
go func() {
cmd := exec.CommandContext(ctx, outputFile)
// Set the user and group ID of the executed program
cmd.SysProcAttr = &syscall.SysProcAttr{
Credential: &syscall.Credential{
Uid: RestrictedUserID,
Gid: RestrictedGroupID,
},
}
// Set the input for the program
cmd.Stdin = strings.NewReader(compileReq.Input)
cmdOutput, err := cmd.CombinedOutput()
if err != nil {
log.Printf("Execution error: %s", err)
}
// Send the execution output through the channel
outputChannel <- cmdOutput
}()
// Remove the temporary output file after the Goroutine completes
defer os.Remove(tmpOpFile.Name())
select {
case <-ctx.Done():
// Execution timed out
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprint(w, "Execution timed out")
log.Println("Execution timed out")
case output := <-outputChannel:
// Execution completed within the timeout duration
w.Header().Set("Content-Type", "text/plain")
w.Write(output)
}
}