iOS 13.4以下版本仍用TLS 1.0/1.1的原因及强制升级TLS 1.2咨询

Great question—this is a common edge case when auditing inbound TLS traffic for iOS devices. Let’s break down the root causes first, then cover actionable fixes depending on whether you’re a developer, enterprise admin, or end user.

Why These Devices Still Use Outdated TLS Protocols #

• App-level configuration overrides: Many older apps (or third-party SDKs embedded in apps) hardcode TLS 1.0/1.1 instead of using the system’s default protocol stack. Developers might have set these values years ago and never updated them, even as iOS evolved.
• System fallback behavior: Prior to iOS 13.4, Apple allowed TLS protocol downgrades if a server didn’t advertise support for TLS 1.2+. So if a device connects to a legacy server that only speaks TLS 1.0/1.1, the system would fall back instead of rejecting the connection.
• Enterprise MDM policies: Some organizations use Mobile Device Management (MDM) to enforce legacy TLS settings for internal servers that haven’t been updated. These policies override the device’s default behavior.
• Legacy certificate trust: If a device has a trusted root certificate that only supports TLS 1.0/1.1, it may use those protocols when connecting to servers signed with that certificate.

How to Enforce TLS 1.2+ on iOS 13.x (Pre-13.4) #

For App Developers #

• Explicitly set minimum TLS versions: In your network code (e.g., NSURLSession), configure the session’s TLSMinimumSupportedProtocolVersion to .TLSv12 to block older protocols. Example snippet:

  let config = URLSessionConfiguration.default
  config.TLSMinimumSupportedProtocolVersion = .TLSv12
  let session = URLSession(configuration: config)
  

• Audit third-party dependencies: Check all SDKs and libraries your app uses—many legacy network libraries default to older TLS versions. Update to their latest versions, or manually override their TLS settings if possible.
• Remove hardcoded protocol locks: Search your codebase for any explicit references to TLSv10 or TLSv11 and replace them with the minimum supported version you want.

For Enterprise Administrators #

• Deploy MDM network security policies: Use your MDM platform to push a network security payload that disables TLS 1.0/1.1. This policy will enforce the minimum protocol across all managed apps and system connections.
• Update internal servers: Migrate enterprise servers to support TLS 1.2+ (and ideally TLS 1.3). Removing the need for fallback eliminates the root cause of protocol downgrades.
• Revoke legacy certificates: Remove any trusted root certificates from devices that only support TLS 1.0/1.1. This forces connections to use certificates compatible with modern TLS protocols.

For End Users #

• Update all apps to their latest versions: Developers often fix TLS configuration issues in app updates, so regularly check the App Store for updates to the apps you use.
• Upgrade iOS to 13.4 or later: Apple tightened TLS restrictions in iOS 13.4, disabling automatic fallback to TLS 1.0/1.1 by default. If your device supports it, upgrading is the simplest long-term fix.

内容的提问来源于stack exchange，提问作者systempuntoout