diff --git a/gallery_dl/extractor/oauth.py b/gallery_dl/extractor/oauth.py
index 48cef94d..55407947 100644
--- a/gallery_dl/extractor/oauth.py
+++ b/gallery_dl/extractor/oauth.py
@@ -14,8 +14,8 @@ from .. import text, oauth, util, config, exception
 from ..output import stdout_write
 from ..cache import cache
 import urllib.parse
+import binascii
 import hashlib
-import base64
 
 REDIRECT_URI_LOCALHOST = "http://localhost:6414/"
 REDIRECT_URI_HTTPS = "https://mikf.github.io/gallery-dl/oauth-redirect.html"
@@ -392,9 +392,9 @@ class OAuthPixiv(OAuthBase):
         yield Message.Version, 1
 
         code_verifier = util.generate_token(32)
-        digest = hashlib.sha256(code_verifier.encode("ascii")).digest()
-        code_challenge = base64.urlsafe_b64encode(
-            digest).rstrip(b"=").decode("ascii")
+        digest = hashlib.sha256(code_verifier.encode()).digest()
+        code_challenge = binascii.b2a_base64(
+            digest)[:-2].decode().replace("+", "-").replace("/", "_")
 
         url = "https://app-api.pixiv.net/web/v1/login"
         params = {
diff --git a/gallery_dl/extractor/photobucket.py b/gallery_dl/extractor/photobucket.py
index 375b5e3c..6234e6a9 100644
--- a/gallery_dl/extractor/photobucket.py
+++ b/gallery_dl/extractor/photobucket.py
@@ -10,7 +10,7 @@
 
 from .common import Extractor, Message
 from .. import text, exception
-import base64
+import binascii
 import json
 
 
@@ -168,7 +168,7 @@ class PhotobucketImageExtractor(Extractor):
         image["titleOrFilename"] = image["title"] or name
         image["tags"] = image.pop("clarifaiTagList", [])
 
-        mtype, _, mid = base64.b64decode(image["id"]).partition(b":")
+        mtype, _, mid = binascii.a2b_base64(image["id"]).partition(b":")
         image["pictureId"] = mid.decode() if mtype == b"mediaId" else ""
 
         yield Message.Directory, image
diff --git a/gallery_dl/oauth.py b/gallery_dl/oauth.py
index e9dfff02..ac38c4dc 100644
--- a/gallery_dl/oauth.py
+++ b/gallery_dl/oauth.py
@@ -10,10 +10,10 @@
 
 import hmac
 import time
-import base64
 import random
 import string
 import hashlib
+import binascii
 import urllib.parse
 
 import requests
@@ -100,7 +100,7 @@ class OAuth1Client(requests.auth.AuthBase):
         key = concat(self.consumer_secret, self.token_secret or "").encode()
         signature = hmac.new(key, message, hashlib.sha1).digest()
 
-        return quote(base64.b64encode(signature).decode())
+        return quote(binascii.b2a_base64(signature)[:-1].decode())
 
 
 class OAuth1API():