2fa is a two-factor authentication agent.
go get -u rsc.io/2fa 2fa -add [-7] [-8] [-hotp] name 2fa -list 2fa name
2fa -add name adds a new key to the 2fa keychain with the given name. It prints a prompt to standard error and reads a two-factor key from standard input. Two-factor keys are short case-insensitive strings of letters A-Z and digits 2-7.
By default the new key generates time-based (TOTP) authentication codes; the
-hotp flag makes the new key generate counter-based (HOTP) codes instead.
By default the new key generates 6-digit codes; the
-8 flags select 7- and 8-digit codes instead.
2fa -list lists the names of all the keys in the keychain.
2fa name prints a two-factor authentication code from the key with the given name. If
-clip is specified,
2fa also copies to the code to the system clipboard.
With no arguments,
2fa prints two-factor authentication codes from all known time-based keys.
The default time-based authentication codes are derived from a hash of the key and the current time, so it is important that the system clock have at least one-minute accuracy.
The keychain is stored unencrypted in the text file
During GitHub 2FA setup, at the “Scan this barcode with your app” step, click the “enter this text code instead” link. A window pops up showing “your two-factor secret,” a short string of letters and digits.
Add it to 2fa under the name github, typing the secret at the prompt:
$ 2fa -add github 2fa key for github: nzxxiidbebvwk6jb $
Then whenever GitHub prompts for a 2FA code, run 2fa to obtain one:
$ 2fa github 268346 $
Or to type less:
$ 2fa 268346 github $