iOS Ignores Critical X509v3 Name Constraints

Number:rdar://18461300 Date Originated:25-Sep-2014 03:36 PM
Status:Duplicate of 10112492 (Open) Resolved:
Product:iOS Product Version:8.0
Classification:Security Reproducible:Always
18461300iOS Ignores Critical X509v3 Name Constraints
iOSState: Open
Rank:No Value
Alfred Karl Kornel25-Sep-2014 03:36 PM

Summary: iOS does not seem to enforce DNS Name Constraints specified by a root certificate.  That's fine, as long as such constraints are not marked as critical.  If iOS encounters a trusted root containing a critical Name Constraints extension, iOS will still allow connections to servers whose SSL certificate does not match the name constraints of the issuing CA.

Steps to Reproduce: 1: Install the CA from the following URL:
The Settings app will warn that the CA cannot be verified.  That is OK.
2: Browse to the following site:
3: Browse to the following site:

Expected Results: I expected Safari to refuse to load either site, because the sites were using certs issued by a root containing a critical extension which iOS is not able to honor.

Actual Results: Safari displayed both web pages, including the lock icon indicating that the connection was secure.

Version: iOS 8.0 (12A365)

Notes: The test servers I made which demonstrate this issue will probably not be up for more than 30 days, unless I can remember to regenerate the CRL for the test CA.

Configuration: IPhone 5 16 GB Sprint


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