CVE-2022-23651

Local race condition in b2-sdk-python <= 1.14.0 exposes API keys

• CVSS 4.7
• CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
• Race Conditions
• Local

b2-sdk-python is a python library to access cloud storage provided by backblaze. Linux and Mac releases of the SDK version 1.14.0 and below contain a key disclosure vulnerability that, in certain conditions, can be exploited by local attackers through a time-of-check-time-of-use (TOCTOU) race condition. SDK users of the SqliteAccountInfo format are vulnerable while users of the InMemoryAccountInfo format are safe. The SqliteAccountInfo saves API keys (and bucket name-to-id mapping) in a local database file ($XDG_CONFIG_HOME/b2/account_info, ~/.b2_account_info or a user-defined path). When first created, the file is world readable and is (typically a few milliseconds) later altered to be private to the user. If the directory containing the file is readable by a local attacker then during the brief period between file creation and permission modification, a local attacker can race to open the file and maintain a handle to it. This allows the local attacker to read the contents after the file after the sensitive information has been saved to it. Consumers of this SDK who rely on it to save data using SqliteAccountInfo class should upgrade to the latest version of the SDK. Those who believe a local user might have opened a handle using this race condition, should remove the affected database files and regenerate all application keys. Users should upgrade to b2-sdk-python 1.14.1 or later.

CVE

CVE-2022-23651

CWE

CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

CVSS base score

4.7

Published

2022-02-23

OWASP

A08 Software and Data Integrity Failures

Orthogonal defect classification

Timing/Serialization

Code defect classification

Timing Issues

Category

Race Conditions

Subcategory

Race Condition in File Operations

Accessibility scope

Local

Impact

Information Disclosure

Fixed by upgrading

Yes

Solution

Upgrade to b2-sdk-python 1.14.1 or later.

import os
import sqlite3

class AccountInfo:
    def __init__(self, db_path):
        self.db_path = db_path
        self.create_database()

    def create_database(self):
        with open(self.db_path, 'w') as db_file:
            pass

        self.connection = sqlite3.connect(self.db_path)
        self.cursor = self.connection.cursor()
        self.cursor.execute('CREATE TABLE IF NOT EXISTS account_info (key TEXT, value TEXT)')

    def store_key(self, key, value):
        self.cursor.execute('INSERT INTO account_info (key, value) VALUES (?, ?)', (key, value))
        self.connection.commit()

    def close(self):
        self.connection.close()

db_path = os.path.expanduser('~/.b2_account_info')
account_info = AccountInfo(db_path)
account_info.store_key('api_key', 'your_api_key_here')
account_info.close()

import os
import sqlite3
import stat
import time

class AccountInfo:
    def __init__(self, db_path):
        self.db_path = db_path
        self.create_database()

    def create_database(self):
        with open(self.db_path, 'w') as db_file:
            pass

        time.sleep(0.1)

        os.chmod(self.db_path, stat.S_IRUSR | stat.S_IWUSR)

        self.connection = sqlite3.connect(self.db_path)
        self.cursor = self.connection.cursor()
        self.cursor.execute('CREATE TABLE IF NOT EXISTS account_info (key TEXT, value TEXT)')

    def store_key(self, key, value):
        self.cursor.execute('INSERT INTO account_info (key, value) VALUES (?, ?)', (key, value))
        self.connection.commit()

    def close(self):
        self.connection.close()

db_path = os.path.expanduser('~/.b2_account_info')
account_info = AccountInfo(db_path)
account_info.store_key('api_key', 'your_api_key_here')
account_info.close()

@misc{vaitp:cve202223651,
  title        = {{Local race condition in b2-sdk-python <= 1.14.0 exposes API keys}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2022},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2022-23651},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2022-23651/}}
}