iOS 13 TLS issue

I'm going to add some additional information. To check that your certificate is valid you can open it in Keychain Access and check that it contains correct information:

  • It expires in less than 825 days;
  • Signature algorithm isn't SHA-1 (SHA-256, probably);
  • Public key size isn't smaller than 2048 bits;
  • There's Extended Key Usage extension with "Server Authentication" purpose;
  • There's Subject Alternative Name extension that contains server's DNS.

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Config example for OpenSSL:

[ ca ]
default_ca = CA_default
[ CA_default ]
default_md = sha256
default_days = 825
[ req ]
prompt             = no
default_bits       = 4096
distinguished_name = req_distinguished_name
x509_extensions     = req_ext
[ req_distinguished_name ]
countryName                = ...
stateOrProvinceName        = ...
localityName               = ...
organizationName           = ...
commonName                 =
[ req_ext ]
extendedKeyUsage = serverAuth
subjectAltName = @alt_names
DNS.1 =
DNS.2 =

To generate new key-certificate pair run this command:

openssl req -newkey rsa:4096 -nodes -keyout key.pem -x509 -out certificate.crt -days 825 -config config.cnf

Apple has defined stricter rules for TLS server certificates, starting from iOS 13 and macOS 10.15.

All TLS server certificates must comply with these new security requirements in iOS 13 and macOS 10.15:

TLS server certificates and issuing CAs using RSA keys must use key sizes greater than or equal to 2048 bits. Certificates using RSA key sizes smaller than 2048 bits are no longer trusted for TLS.

TLS server certificates and issuing CAs must use a hash algorithm from the SHA-2 family in the signature algorithm. SHA-1 signed certificates are no longer trusted for TLS.

TLS server certificates must present the DNS name of the server in the Subject Alternative Name extension of the certificate. DNS names in the CommonName of a certificate are no longer trusted.

Additionally, all TLS server certificates issued after July 1, 2019 (as indicated in the NotBefore field of the certificate) must follow these guidelines:

TLS server certificates must contain an ExtendedKeyUsage (EKU) extension containing the id-kp-serverAuth OID.

TLS server certificates must have a validity period of 825 days or fewer (as expressed in the NotBefore and NotAfter fields of the certificate).

And the final note:

Connections to TLS servers violating these new requirements will fail and may cause network failures, apps to fail, and websites to not load in Safari in iOS 13 and macOS 10.15.