SSL Error When installing rubygems, Unable to pull data from 'https://rubygems.org/

For RVM & OSX users

Make sure you use latest rvm:

rvm get stable

Then you can do two things:

1. Update certificates:

   rvm osx-ssl-certs update all
   

2. Update rubygems:

   rvm rubygems latest
   

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For non RVM users

Find path for certificate:

cert_file=$(ruby -ropenssl -e 'puts OpenSSL::X509::DEFAULT_CERT_FILE')

Generate certificate:

security find-certificate -a -p /Library/Keychains/System.keychain > "$cert_file"
security find-certificate -a -p /System/Library/Keychains/SystemRootCertificates.keychain >> "$cert_file"

The whole code: https://github.com/wayneeseguin/rvm/blob/master/scripts/functions/osx-ssl-certs

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For non OSX users

Make sure to update package ca-certificates. (on old systems it might not be available - do not use an old system which does not receive security updates any more)

Windows note

The Ruby Installer builds for windows are prepared by Luis Lavena and the path to certificates will be showing something like C:/Users/Luis/... check https://github.com/oneclick/rubyinstaller/issues/249 for more details and this answer https://stackoverflow.com/a/27298259/497756 for fix.

Latest findings...

https://gist.github.com/luislavena/f064211759ee0f806c88

Most importantly...download https://raw.githubusercontent.com/rubygems/rubygems/master/lib/rubygems/ssl_certs/rubygems.org/AddTrustExternalCARoot-2048.pem

Figure out where to stick it

C:\>gem which rubygems
C:/Ruby21/lib/ruby/2.1.0/rubygems.rb

Then just copy the .pem file in ../2.1.0/rubygems/ssl_certs/ and go on about your business.

For windows users

Goto link http://rubygems.org/pages/download

1. Download the latest zip file (In my case 2.4.5)
2. Unzip it
3. run "ruby setup.rb" in unzipped folder
4. now run gem install command