react-native-cert-pinner
This package manages TLS certificate pinning in react-native for Android and iOS.
Getting started
$ npm install react-native-cert-pinner --save
Mostly automatic installation
$ react-native link react-native-cert-pinner
Manual installation
iOS
Add the following line to the project targets in your Podfile
:
pod 'TrustKit', '~> 1.4.2'
Then run pod install.
Android
- Open up
android/app/src/main/java/[...]/MainApplication.java
- Add
import com.criticalblue.reactnative.CertPinnerPackage;
to the imports at the top of the file - Add
new CertPinnerPackage()
to the list returned by thegetPackages()
method
- Append the following lines to
android/settings.gradle
:include ':react-native-cert-pinner' project(':react-native-cert-pinner').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-cert-pinner/android')
- Insert the following lines inside the dependencies block in
android/app/build.gradle
:compile project(':react-native-cert-pinner')
Usage
To use the react-native networking utilities, like fetch()
, certificate pinning must be done in the native app before the app's react-native javascript is run.
Unlike typical installed packages, there is no need to require any modules in the javascript. Everything is setup and enforced inside the native module.
Certificate Pinning Configuration
A pinset
utility is provided to help configure the native modules for pinning.
The default setup assumes you are running in your project's home directory. The default configuration file is ./pinset.json
, and the default native android project is assumed to be located at ./android
. Both these locations may be overriden on the command line.
Command Help
To get help:
$ npx pinset -h
pinset [command] [options]
init ..... initialize pinset configuration
gen ...... generate pinset configuration
version .. show package version
help ..... show help menu for a command
or for a sub-command:
$ npx pinset help gen
pinset gen [options] [config]
--android, -a <path> .. path to Android project (defaults to './android')
--ios, -i <path> ...... path to iOS project (defaults to './ios')
--force, -f ........... always overwrite existing configuration
config ................ configuration file - defaults to 'pinset.json'
Initialization
The first step is to generate a starter configuration:
$ npx pinset init
This command will not overwrite an existing configuration file unless the --force
flag is used.
Lookup
Next, determine which URLs you want to pin, and determine each certificate's public key hash. A convenient utility is provided by Report URI at https://report-uri.com/home/pkp_hash. Enter a URL to see the current chain of certificate hashes.
Enter the desired public key hashes into the pinset.json
file:
Note:
-
enforcePinning
is added into the domain config to enable the diabling of PIN validation. -
selfSignedCerts
is added on the same level as the domains (see example), to allow the setting of public keys of SELF-SIGNED certificates. Ensure that these self-signed certificates are available publicly. If they are not, they should not be added here. If not, the app will crash.- Adding these certs will help the server to validate the PINs. Server cannot validate PINs of self-signed certs as these certs are not publicly trusted. Thus, if the public keys of these certs are added here, the server can decode them to obtain the necessary information to validate the PIN. Beware that this only works if the self-signed servers are pubicly accessible. If they are local secured servers, it will not work and cause the app to crash.
{
"domains": {
"*.approov.io": {
"pins": [
"sha256/0000000000000000000000000000000000000000000",
"sha256/1111111111111111111111111111111111111111111"
]
},
"*.criticalblue.com": {
"pins": [
"sha256/2222222222222222222222222222222222222222222",
"sha256/3333333333333333333333333333333333333333333"
]
},
"*.southeastasia.cloudapp.azure.com": {
"pins": ["sha256/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"],
"enforcePinning": false // Disable pinning. Use this when you do not want to validate the server certificate, especially in the case of self-signed or unsecured servers.
}
},
"selfSignedCerts": [] // Base-64 PEM key of the cert. This should only be used for self-signed servers. To obtain this key, use the command `openssl s_client -showcerts -connect <server_name>:<port>` (server_name can be `dev.workforceoptimizer.com`, port should be 443, the default port for secured servvers). The key lies between the -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----
}
Domains starting with*.
will include all subdomains.
It is recommended to select multiple hashes with at least one of them being from an intermediate certificate.
Generation
Once the configuration is set, generate the native project sources:
$ npx pinset gen
Reading config file './pinset.json'.
Updating java file './android/app/src/main/java/com/criticalblue/reactnative/GeneratedCertificatePinner.java'.
Updating plist file './ios/example/info.plist'.
Build and run the react-native app, for example:
$ react-native run-ios
Updates
To update the certificate pins, edit the configuration file, regenerate the native sources, and rebuild the app.
Note, there is no way to update the pin sets from javascript while the app is running.
Certificate Security
If you consider publishing hashes of public key certificates to be a security breach, you may want to remove or ignore the pinset configuration and generated fines from your repository.
To ignore the default files in a git repository, add to .gitignore
:
# default configuration file
./pinset.json
# default generated android source
./android/app/src/main/java/com/criticalblue/reactnative/GeneratedCertificatePinner.java
./ios/<your project here>/info.plist
Debugging
- Open a git bash console
- Type command
adb logcat -s ADInterceptor
. Log messages under the tag nameADInterceptor
will appear. - The log will commonly start with some initialisation messages:
Getting All Issuers, Count = <number_of_trusted_issuers>
(number_of_trusted_issuers
is usually 137)
Generated Certficate Pinner in use
Self signed certs: <number_of_registered_self_signed_certs>
(number_of_registered_self_signed_certs
is the number of entries in the selfSignedCerts
attribute of the pinset.json
file.)
- Interceptor will start with the log message
Verifying hostname
, followed by the log messageIntercepting
. - If the server is properly signed with a trusted CA, the log message
Pass validation - HOST: <host_name>
will be shown, e..gPass validation - HOST: qa.workforceoptimizer.com
. - If the server is self-signed, an unsecured one, or is not pinned, an error log message with the error will be displayed
Failed validation - HOST: <host_name>, <error_message>
. - If the validation fails, but the server has the enablePinning set to false, this log message
Pinning is disabled for this PIN: <sha256_pin>
will show up. If not, this error log messagePinning is enabled for this host. Connection aborted.
will show up.