One self-signed cert to rule them all? Chrome, Android, and iOS

Question

Yet another self-signed cert question, but I've tried for several days to find the best/correct way to create a self-signed cert that will work in my development environment for the latest versions of Chrome, Android, and iOS.

The instructions I've found here and elsewhere are outdated for at least one of these platforms.

Here is the best I've found, but it only works with Chrome and Android.

openssl req -new -newkey rsa:2048 -days 3650 -nodes -x509 -subj "/C=US/ST=Oklahoma/L=Stillwater/O=My Company/OU=Engineering" -keyout ca.key -out ca.crt
openssl genrsa -out "test.key" 2048
openssl req -new -key test.key -out test.csr -config openssl.cnf
openssl x509 -req -days 3650 -in test.csr -CA ca.crt -CAkey ca.key -CAcreateserial -extensions v3_req -extfile openssl.cnf -out test.crt
openssl x509 -inform PEM -outform DER -in test.crt -out test.der.crt

Contents of openssl.cnf:

[req]
default_bits = 2048
encrypt_key  = no # Change to encrypt the private key using des3 or similar
default_md   = sha256
prompt       = no
utf8         = yes

# Specify the DN here so we aren't prompted (along with prompt = no above).

distinguished_name = req_distinguished_name

# Extensions for SAN IP and SAN DNS

req_extensions = v3_req

# Be sure to update the subject to match your organization.

[req_distinguished_name]
C  = US
ST = Oklahoma
L  = Stillwater
O  = My Company
OU = Engineering
CN = test.com

# Allow client and server auth. You may want to only allow server auth.
# Link to SAN names.

[v3_req]
basicConstraints     = CA:TRUE
subjectKeyIdentifier = hash
keyUsage             = digitalSignature, keyEncipherment
extendedKeyUsage     = clientAuth, serverAuth
subjectAltName       = @alt_names

# Alternative names are specified as IP.# and DNS.# for IP addresses and
# DNS accordingly.

[alt_names]
DNS.1 = test.com

After installing test.crt and test.key on my development server, this method works great for Chrome: just added test.crt to my Mac's keychain and turned on "Always Trust" for it.

It also works great for Android: emailed test.der.crt to the device and tapped it to install. Most important: it showed up in the "USER" tab under Settings / Encryption & credentials / Trusted credentials. This is essential for using networkSecurityConfig in my Android app.

Unfortunately it didn't work for iOS:

• I installed it in an Xcode simulator by dragging the certificates to it.
• I had to install both test.crt and ca.crt. If I just installed test.crt, it remained in "unverified" status, which makes sense since the ca.crt is the root certificate.
• It did not show up under Settings / About / Certificate Trust Settings which is required for me to turn it on.
• When my app tries to access my server with NSMutableURLRequest, it gets a "TIC SSL Trust Error" with 10 key-value pairs, including:
  • NSURLErrorFailingURLPeerTrustErrorKey=
  • _kCFStreamErrorDomainKey=3
  • _kCFStreamErrorCodeKey=-9813
  • NSErrorPeerCertificateChainKey=1 element, and NSLocalizedDescription=The certificate for this server is invalid. You might be connecting to a server that is pretending to be “test.com” which could put your confidential information at risk.

Any idea how to change what I did so I can turn it on for iOS under "Certificate Trust Settings"?

Note 1: Since other answers to other questions about the -9813 error code suggested there may be a missing intermediate certificate, I added ca.crt to my Apache configuration for the SSLCaCertificateFile setting. It still worked fine for Chrome and Android, but had exactly the same error in iOS.

Thanks!

Answer 1

This answer has been updated (and simplified) to be compatible with iOS 13 and Android 8. Credit now goes to https://discussions.apple.com/thread/250666160 answer by user:fixitnowyes on October 6, 2019.

Just one openssl command works to create a self-signed certificate that works in Chrome, Android, and iOS:

openssl req -config openssl.cnf -new -x509 -days 825 -out ca.crt

This outputs both ca.crt and ca.key. Note that 825 days is the maximum duration allowed by iOS 13+, and it must be specified in the openssl command. The days setting in openssl.cnf does not do anything that I can tell.

Check information about the certificate with:

openssl x509 -in ca.crt -text -noout

Contents of openssl.cnf:

[ req ]
default_bits        = 2048
default_keyfile     = ca.key
default_md          = sha256
default_days        = 825
encrypt_key         = no
distinguished_name  = subject
req_extensions      = req_ext
x509_extensions     = x509_ext
string_mask         = utf8only
prompt              = no

# The Subject DN can be formed using X501 or RFC 4514 (see RFC 4519 for a description).
#   Its sort of a mashup. For example, RFC 4514 does not provide emailAddress.

[ subject ]
countryName                 = US
stateOrProvinceName         = Oklahoma
localityName                = Stillwater
organizationName            = My Company
OU                          = Engineering

# Use a friendly name here because it's presented to the user. The server's DNS
#   names are placed in Subject Alternate Names. Plus, DNS names here is deprecated
#   by both IETF and CA/Browser Forums. If you place a DNS name here, then you
#   must include the DNS name in the SAN too (otherwise, Chrome and others that
#   strictly follow the CA/Browser Baseline Requirements will fail).

commonName              = test.com
emailAddress            = me@home.com

# Section x509_ext is used when generating a self-signed certificate. I.e., openssl req -x509 ...

[ x509_ext ]
subjectKeyIdentifier      = hash
authorityKeyIdentifier    = keyid:always,issuer

# You only need digitalSignature below. *If* you don't allow
#   RSA Key transport (i.e., you use ephemeral cipher suites), then
#   omit keyEncipherment because that's key transport.

basicConstraints        = critical, CA:TRUE
keyUsage            = critical, digitalSignature, keyEncipherment, cRLSign, keyCertSign
subjectAltName          = DNS:test.com
extendedKeyUsage = serverAuth

# RFC 5280, Section 4.2.1.12 makes EKU optional
#   CA/Browser Baseline Requirements, Appendix (B)(3)(G) makes me confused
#   In either case, you probably only need serverAuth.

extendedKeyUsage    = TLS Web Server Authentication

# Section req_ext is used when generating a certificate signing request. I.e., openssl req ...

[ req_ext ]
subjectKeyIdentifier        = hash
basicConstraints        = CA:FALSE
keyUsage            = digitalSignature, keyEncipherment
subjectAltName          = DNS:test.com
nsComment           = "OpenSSL Generated Certificate"

# RFC 5280, Section 4.2.1.12 makes EKU optional
#   CA/Browser Baseline Requirements, Appendix (B)(3)(G) makes me confused
#   In either case, you probably only need serverAuth.
# extendedKeyUsage    = serverAuth, clientAuth

# [ alternate_names ]
# DNS.1       = example.com
# DNS.2       = www.example.com
# DNS.3       = mail.example.com
# DNS.4       = ftp.example.com


# Add these if you need them. But usually you don't want them or
#   need them in production. You may need them for development.
# DNS.5       = localhost
# DNS.6       = localhost.localdomain
# DNS.7       = 127.0.0.1

# IPv6 localhost
# DNS.8     = ::1

After creating the certificates...

Server installation:

1. Install ca.crt and ca.key in your server.
2. Restart server.

Chrome / Safari installation:

1. Add ca.crt to your Mac's KeyChain Access in the System keychain (or PC equivalent).
2. Set it to "Always Trust" (in Mac) so that it works in Chrome and Safari.

iOS device installation:

1. Send ca.crt to your device and download it to Files
2. Go to Files and open ca.crt
3. Go to General / VPN & Device Management, find your cert (listed by domain), and install it
4. Go to General / About / Certificate Trust Settings and turn on the certificate

iOS Xcode simulator installation:

1. Drag ca.crt to the simulator. Note that there is no confirmation that anything happened.
2. There should be no need to go to Settings / General / About / Certificate Trust Settings and enable it. It should be already enabled.

Android installation:

1. Email ca.crt to your Gmail account, then log into Gmail in your Android simulator and tap to install it.
2. It should appear in the "USER" tab under Settings / Lock screen & security / Encryption & credentials / Trusted credentials.

Answer 2

I'll share my batch file for creating self signed certificates that work on Windows, iOS, Android, Chrome, FireFox and Safari. I've tested on the latest versions of Chrome, Firefox and the native browsers on mobile (Android 8.1, Latest iOS).

I found the accepted answer wasn't quite covering some scenarios - I still had to accept an exception on some mobile versions of Firefox. Although accepting the exception shows the lock icon this would cause the url to show in PWAs when installed as fullscreen or standalone modes. My goal was to support an intranet with no exceptions in order to have proper PWA installations on a private local network.

What I found covered all scenarios (real devices) tested was;

• creating a CA
• creating a signing request
• creating a CERT with the signing request
• binding the CERT to the website
• installing the CA on all devices.

Note: The batch file creates a lot of files but many of them are just different formats to support different scenarios. The batch file will ask for a password several times. Don't get confused by entering multiple passwords - as the batch file progresses through steps it's always verifying the initial password created on step one. If you run into an error through a pause at the end of the batch file.

SelfCert.bat

:: Please install openssl in c:\openssl
:: The path to config should be C:\openssl\openssl.cnf
:: Otherwise you will need to add -config "path to openssl.cnf" when making requests

:: Change to current directory of batch file
cd %~dp0

:: GENERATING CA
:: 1.Generate RSA
openssl genrsa -aes256 -out ca-key.pem 4096

:: 2.Generate a public CA Cert
openssl req -new -x509 -sha256 -days 365 -key ca-key.pem -out ca.pem

:: GENERATING CERTIFICATE
:: 1. Create a RSA key
openssl genrsa -out cert-key.pem 4096

:: 2. Create a Certificate Signing Request (CSR)
openssl req -new -sha256 -subj "/CN=yourcngoeshere" -key cert-key.pem -out cert.csr

:: 3. Create a extfile with all the alternative names
:: OBSOLETE HANDLED IN C#
:: echo "subjectAltName=DNS:your-dns.record,IP:XXX.XXX.XXX.XXX" >> extfile.cnf

:: 4. Create the Certificate
openssl x509 -req -sha256 -days 365 -in cert.csr -CA ca.pem -CAkey ca-key.pem -out cert.pem -extfile extfile.cnf -CAcreateserial

:: At this point the chian is completed.Now we will create different formats for uses cases and add to trusted root.

:: 5. Create a crt for Android
openssl x509 -outform der -in ca.pem -out ca.crt

:: 6. Create a pfx for IIS, Kestrel
openssl pkcs12 -export -out cert.pfx -inkey cert-key.pem -in cert.pem -certfile ca.pem

:: 7. Add the certification to our trusted root (iOS can add crt or pem)
certutil.exe -addstore root ca.pem

:: Remember in iOS to enable the certificate after installing it
:: Settings > General > About > Certificate Trust Settings

extfile.cnf

I create this file before running the batch file but you could uncomment step 3 under GENERATING CERTIFICATE.

subjectAltName=DNS:your-dns.record,IP:XXX.XXX.XXX.XXX

Server / Client - Windows

• On Windows the CA is added to the Trusted Root on the last line of the batch file certutil.exe -addstore root ca.pem.

• On IIS and Kestrel I assign the cert.pfx to the website.

builder.WebHost.ConfigureKestrel(opt => { opt.ListenAnyIP(6001, listOpt => { listOpt.UseHttps(@"path to cert.pfx", "pfxpassword");});});

Client - Android

• On Android I email the ca.crt. Some versions of Android seem to be picky about the type. Clicking the attachment from the email is enough to install it.
• Verify it's installed by nagivating to Settings > Security & Location > Encryption & credentials > Trusted Credentials > User.
  • If not you may need to go to Settings > Security & Location > Encryption & credentials > Install from SD Card > Downloads

Client - iOS

• On iOS I email the ca.crt or the ca.pem. Be sure to follow the prompted instructions for enabling the CA after installation.
  • Usually after downloading you need to go to Settings > General > Profiles > Install
  • After installing it you need to go to Settings > General > About > Certificate Trust Settings > Enable Certificate

Two days ago I dove into certification chains and having no experience in cryptography really hurt my brain. Major credits go to Christian Lempa. I just put his commands into a batch file and converted them to different formats at the end. Hopefully this helps someone out.