Merge pull request 'feat/interactive-auth' (#9) from feat/interactive-auth into main

Reviewed-on: #9

README.md

@@ -26,15 +26,16 @@ go build -o canvasarchiver ./cmd/canvasarchiver
    ./canvasarchiver -fo
    ```
 
-   Or for videos-only mode (all Panopto videos flat, no files):
-   ```bash
-   ./canvasarchiver -vo
-   ```
+    Or for videos-only mode (all Panopto videos flat, no files):
+    ```bash
+    ./canvasarchiver -vo
+    ```
 
-2. On first run, you'll be prompted to authenticate:
-   - Visit the provided OAuth URL
-   - Authorize the application
-   - Copy the authorization code back to the terminal
+2. On first run, you'll be prompted to choose an authentication method:
+   - **[1] Login via browser (OAuth)**: Visit the provided URL, authorize, and paste the code
+   - **[2] Use Canvas API token**: Enter a manually generated API token (e.g. `12230~...`)
+
+   The choice is saved and reused on subsequent runs.
 
 3. Enter your Course ID when prompted (or use `-me` to download all enrolled courses)
 
@@ -54,7 +55,6 @@ go build -o canvasarchiver ./cmd/canvasarchiver
 | `-me` | Download all enrolled courses |
 | `-n` | Prefix modules with order numbers `[1]`, `[2]`, etc. |
 
-
 ## Configuration
 
 The following constants can be modified in `internal/config/config.go`:
@@ -66,7 +66,7 @@ The following constants can be modified in `internal/config/config.go`:
 
 ## Authentication
 
-Credentials are stored in `credentials.json` after the first successful login. The refresh token is automatically used for subsequent runs.
+Credentials are stored in `credentials.json` after the first successful authentication. The chosen method is remembered for subsequent runs — OAuth refresh tokens are automatically refreshed, and API tokens are validated before saving.
 
 ## Notes
 

cmd/canvasarchiver/main.go

@@ -22,7 +22,7 @@ func main() {
 	httpClient := &http.Client{}
 
 	authenticator := auth.NewAuthenticator(httpClient)
-	accessToken, err := authenticator.GetAccessToken()
+	accessToken, err := authenticator.GetToken()
 	if err != nil {
 		fmt.Printf("Authentication failed: %v\n", err)
 		return

internal/auth/auth.go

@@ -1,11 +1,17 @@
 package auth
 
 import (
+	"bufio"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/url"
 	"os"
+	"strings"
 
 	"git.directme.in/Joren/CanvasArchiver/internal/config"
 	"git.directme.in/Joren/CanvasArchiver/internal/models"
@@ -21,31 +27,38 @@ func NewAuthenticator(client *http.Client) *Authenticator {
 	}
 }
 
-func (a *Authenticator) GetAccessToken() (string, error) {
+func (a *Authenticator) GetToken() (string, error) {
+	creds, err := LoadCredentials()
+	if err == nil && creds.AuthMethod != "" {
+		switch creds.AuthMethod {
+		case "api":
+			token := strings.TrimSpace(creds.APIToken)
+			if token == "" {
+				return a.promptMethod()
+			}
+			fmt.Print("[*] Validating saved API token... ")
+			if err := a.validateAPIToken(token); err != nil {
+				fmt.Println("FAILED")
+				fmt.Printf("[!] %v\n", err)
+				SaveCredentials(&models.Credentials{})
+				return a.promptMethod()
+			}
+			fmt.Println("OK")
+			return token, nil
+		case "oauth":
+			return a.refreshOrLogin()
+		}
+	}
+	return a.promptMethod()
+}
+
+func (a *Authenticator) refreshOrLogin() (string, error) {
 	creds, err := LoadCredentials()
 	if err != nil {
-
-		fmt.Println("--- Initial Canvas Login Required ---")
-		fmt.Printf("Visit: %s/login/oauth2/auth?client_id=%s&response_type=code&redirect_uri=%s\n",
-			config.BaseURL, config.ClientID, url.QueryEscape(config.RedirectURI))
-		fmt.Print("Enter Code: ")
-		var code string
-		fmt.Scanln(&code)
-
-		tr, err := a.doTokenRequest(url.Values{
-			"grant_type":    {"authorization_code"},
-			"client_id":     {config.ClientID},
-			"client_secret": {config.ClientSecret},
-			"redirect_uri":  {config.RedirectURI},
-			"code":          {code},
-		})
-		if err != nil {
-			return "", err
-		}
-
-		SaveCredentials(&models.Credentials{RefreshToken: tr.RefreshToken})
-		fmt.Println("[+] Login successful.")
-		return tr.AccessToken, nil
+		return a.login()
+	}
+	if strings.TrimSpace(creds.RefreshToken) == "" {
+		return a.login()
 	}
 
 	fmt.Println("[*] Reusing saved refresh token...")
@@ -54,11 +67,111 @@ func (a *Authenticator) GetAccessToken() (string, error) {
 		"client_id":     {config.ClientID},
 		"client_secret": {config.ClientSecret},
 		"refresh_token": {creds.RefreshToken},
+		"redirect_uri":  {config.RedirectURI},
+	})
+	if err != nil {
+		fmt.Printf("[!] Refresh failed: %v\n", err)
+		return a.login()
+	}
+	fmt.Println("[+] Session refreshed.")
+	return tr.AccessToken, nil
+}
+
+func (a *Authenticator) promptMethod() (string, error) {
+	fmt.Println("Select authentication method:")
+	fmt.Println("  [1] Login via browser (OAuth)")
+	fmt.Println("  [2] Use Canvas API token")
+	fmt.Print("Choice (1/2): ")
+	input, err := bufio.NewReader(os.Stdin).ReadString('\n')
+	if err != nil && err != io.EOF {
+		return "", err
+	}
+	switch strings.TrimSpace(input) {
+	case "2":
+		return a.setupAPIToken()
+	default:
+		return a.login()
+	}
+}
+
+func (a *Authenticator) setupAPIToken() (string, error) {
+	fmt.Print("Enter Canvas API token: ")
+	token, err := bufio.NewReader(os.Stdin).ReadString('\n')
+	if err != nil && err != io.EOF {
+		return "", err
+	}
+	token = strings.TrimSpace(token)
+	if token == "" {
+		return "", fmt.Errorf("empty API token")
+	}
+
+	fmt.Print("[*] Validating API token... ")
+	if err := a.validateAPIToken(token); err != nil {
+		fmt.Println("FAILED")
+		return "", err
+	}
+	fmt.Println("OK")
+
+	if err := SaveCredentials(&models.Credentials{
+		AuthMethod: "api",
+		APIToken:   token,
+	}); err != nil {
+		return "", err
+	}
+	fmt.Println("[+] API token saved.")
+	return token, nil
+}
+
+func (a *Authenticator) validateAPIToken(token string) error {
+	req, _ := http.NewRequest("GET", config.BaseURL+"/api/v1/users/self", nil)
+	req.Header.Set("Authorization", "Bearer "+token)
+	resp, err := a.HTTPClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		body, _ := io.ReadAll(resp.Body)
+		return fmt.Errorf("invalid token: %d %s", resp.StatusCode, strings.TrimSpace(string(body)))
+	}
+	return nil
+}
+
+func (a *Authenticator) login() (string, error) {
+	codeVerifier, codeChallenge, err := generatePKCEPair()
+	if err != nil {
+		return "", err
+	}
+
+	fmt.Println("--- Initial Canvas Login Required ---")
+	fmt.Printf("Visit: %s\n", buildAuthURL(codeChallenge))
+	fmt.Print("Enter Code or redirect URL: ")
+	input, err := bufio.NewReader(os.Stdin).ReadString('\n')
+	if err != nil && err != io.EOF {
+		return "", err
+	}
+
+	code, err := extractCode(input)
+	if err != nil {
+		return "", err
+	}
+
+	tr, err := a.doTokenRequest(url.Values{
+		"grant_type":    {"authorization_code"},
+		"client_id":     {config.ClientID},
+		"client_secret": {config.ClientSecret},
+		"redirect_uri":  {config.RedirectURI},
+		"code":          {code},
+		"code_verifier": {codeVerifier},
 	})
 	if err != nil {
 		return "", err
 	}
-	fmt.Println("[+] Session refreshed.")
+
+	if err := SaveRefreshToken(tr.RefreshToken); err != nil {
+		return "", err
+	}
+	fmt.Println("[+] Login successful.")
 	return tr.AccessToken, nil
 }
 
@@ -70,17 +183,91 @@ func (a *Authenticator) doTokenRequest(v url.Values) (*models.TokenResponse, err
 	defer resp.Body.Close()
 
 	if resp.StatusCode != 200 {
-		return nil, fmt.Errorf("token request failed: %d", resp.StatusCode)
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("token request failed: %d: %s", resp.StatusCode, string(body))
 	}
 
 	var tr models.TokenResponse
-	json.NewDecoder(resp.Body).Decode(&tr)
+	if err := json.NewDecoder(resp.Body).Decode(&tr); err != nil {
+		return nil, err
+	}
 	return &tr, nil
 }
 
-func SaveCredentials(creds *models.Credentials) {
-	data, _ := json.MarshalIndent(creds, "", "  ")
-	os.WriteFile(config.CredsFile, data, 0o644)
+func buildAuthURL(codeChallenge string) string {
+	u, _ := url.Parse(config.BaseURL + "/login/oauth2/auth")
+	q := u.Query()
+	q.Set("client_id", config.ClientID)
+	q.Set("response_type", "code")
+	q.Set("mobile", "1")
+	q.Set("purpose", config.OAuthPurpose)
+	q.Set("code_challenge", codeChallenge)
+	q.Set("code_challenge_method", "S256")
+	q.Set("redirect_uri", config.RedirectURI)
+	if config.AuthProvider != "" {
+		q.Set("authentication_provider", config.AuthProvider)
+	}
+	u.RawQuery = q.Encode()
+	return u.String()
+}
+
+func generatePKCEPair() (string, string, error) {
+	randomBytes := make([]byte, 64)
+	if _, err := rand.Read(randomBytes); err != nil {
+		return "", "", err
+	}
+
+	verifier := base64.RawURLEncoding.EncodeToString(randomBytes)
+	challengeBytes := sha256.Sum256([]byte(verifier))
+	challenge := base64.RawURLEncoding.EncodeToString(challengeBytes[:])
+	return verifier, challenge, nil
+}
+
+func extractCode(input string) (string, error) {
+	input = strings.TrimSpace(input)
+	if input == "" {
+		return "", fmt.Errorf("empty authorization code")
+	}
+
+	for _, field := range strings.Fields(input) {
+		if strings.Contains(field, "code=") {
+			input = field
+			break
+		}
+	}
+
+	parsedURL, err := url.Parse(input)
+	if err == nil {
+		if code := parsedURL.Query().Get("code"); code != "" {
+			return code, nil
+		}
+	}
+
+	if values, err := url.ParseQuery(input); err == nil {
+		if code := values.Get("code"); code != "" {
+			return code, nil
+		}
+	}
+
+	return input, nil
+}
+
+func SaveCredentials(creds *models.Credentials) error {
+	data, err := json.MarshalIndent(creds, "", "  ")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(config.CredsFile, data, 0o644)
+}
+
+func SaveRefreshToken(refreshToken string) error {
+	creds, err := LoadCredentials()
+	if err != nil {
+		creds = &models.Credentials{}
+	}
+	creds.RefreshToken = refreshToken
+	creds.AuthMethod = "oauth"
+	return SaveCredentials(creds)
 }
 
 func LoadCredentials() (*models.Credentials, error) {
@@ -89,6 +276,8 @@ func LoadCredentials() (*models.Credentials, error) {
 		return nil, err
 	}
 	var creds models.Credentials
-	json.Unmarshal(data, &creds)
+	if err := json.Unmarshal(data, &creds); err != nil {
+		return nil, err
+	}
 	return &creds, nil
 }

internal/canvas/client.go

@@ -16,6 +16,13 @@ import (
 	"git.directme.in/Joren/CanvasArchiver/internal/utils"
 )
 
+func checkAPIResponse(resp *http.Response) error {
+	if resp.StatusCode < 300 {
+		return nil
+	}
+	return fmt.Errorf("API error: %d", resp.StatusCode)
+}
+
 type Client struct {
 	HTTPClient      *http.Client
 	AccessToken     string
@@ -48,6 +55,10 @@ func (c *Client) GetCourseInfo() error {
 	}
 	defer resp.Body.Close()
 
+	if err := checkAPIResponse(resp); err != nil {
+		return err
+	}
+
 	var course models.Course
 	json.NewDecoder(resp.Body).Decode(&course)
 
@@ -64,6 +75,10 @@ func (c *Client) GetEnrolledCourses() ([]models.Course, error) {
 	}
 	defer resp.Body.Close()
 
+	if err := checkAPIResponse(resp); err != nil {
+		return nil, err
+	}
+
 	var courses []models.Course
 	json.NewDecoder(resp.Body).Decode(&courses)
 	return courses, nil

internal/config/config.go

@@ -4,7 +4,9 @@ const (
 	BaseURL      = "https://canvas.vub.be"
 	ClientID     = "170000000000044"
 	ClientSecret = "3sxR3NtgXRfT9KdpWGAFQygq6O9RzLN021h2lAzhHUZEeSQ5XGV41Ddi5iutwW6f"
-	RedirectURI  = "urn:ietf:wg:oauth:2.0:oob"
+	RedirectURI  = "https://sso.canvaslms.com/canvas/login"
+	OAuthPurpose = "CanvasArchiver"
+	AuthProvider = "microsoft"
 	CredsFile    = "credentials.json"
 	PanoptoID    = "15"
 	UserAgent    = "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Mobile Safari/537.36"

internal/models/models.go

@@ -1,7 +1,9 @@
 package models
 
 type Credentials struct {
-	RefreshToken string `json:"refresh_token"`
+	AuthMethod   string `json:"auth_method,omitempty"`
+	RefreshToken string `json:"refresh_token,omitempty"`
+	APIToken     string `json:"api_token,omitempty"`
 }
 
 type TokenResponse struct {