COMMANDS¶

• init: Generate and store a new TOTP secret. Possible options: -b, -l, -N, -p, -P, -T, -s
• show: Calculate and show a TOTP value. Possible options: -N, -t, -T
• reseal: Reseal TOTP secret to new PCRs, banks or values. Possible options: -b, -N, -p, -P (required), -T
• recover: Recover the TOTP secret and display it again. Possible Options: -N, -P (required), -T
• clean: Delete the consumed NV index. Possible Options: -N, -T

OPTIONS¶

• -b <bank>[,<bank>[,...]], --banks <bank>[,<bank>[,...]]: Selected PCR banks (default: SHA1,SHA256)
• -h, --help: Print help
• -l, --label: Label to use for display in the TOTP authenticator app (default: TPM2-TOTP)
• -s, --secret: Specify a custom secret instead of randomly generationg one
• -N <nvindex>, --nvindex <nvindex>: TPM NV index to store data (default: 0x018094AF)
• -p <pcr>[,<pcr>[,...]], --pcrs <pcr>[,<pcr>[,...]]: Selected PCR registers (default: 0,2,4,6)
• -P <password>, --password <password>: Password for the secret (default: none) (commands: init, recover, reseal) Read from stdin if - (recommended). Must not contain \0.
• -t, --time: Display the date/time of the TOTP calculation (commands: show)
• -T <tcti-name>[:<tcti-config>], --tcti <tcti-name>[:<tcti-config>]: Select the TCTI to use. tcti-name is the name of the TCTI library. If present, the configuration string tcti-config is passed verbatim to the chosen TCTI library.

•

-v, --verbose: Print verbose messages

Setup¶

The TOTP secret can be initialized with and without password. It is recommended to set a password -P in order to enable recovery options. Further, it is strongly recommended to provide the password via stdin, rather than directly as a command line option, to protect it from other processes, shell history, etc. Also the PCRs and PCR banks can be selected -p and -b. Default values are PCRs 0,2,4 and banks SHA1, SHA256.

tpm2-totp init
tpm2-totp -P - init
verysecret<CTRL-D>
# or (recommended)
gpg --decrypt /path/to/password.gpg | tpm2-totp -P - init
# or (discouraged)
tpm2-totp -P verysecret init
tpm2-totp -P - -p 0,1,2,3,4,5,6 init
tpm2-totp -p 0,1,2,3,4,5,6 -b SHA1,SHA256 init
    

Boot¶

During boot the TOTP value for the current time, together with the current time should be shown to the user, e.g. using plymouth from mkinitrd or from dracut. The command to be executed is:

tpm2-totp show
tpm2-totp -t show
    

Recovery¶

In order to recover the QR code:

tpm2-totp -P - recover
    

In order to reseal the secret:

tpm2-totp -P - reseal
tpm2-totp -P - -p 1,3,5,6 reseal
    

Deletion¶

In order to delete the created NV index:

tpm2-totp clean
    

NV index¶

All command additionally take the -N option to specify the NV index to be used. By default, 0x018094AF is used and recommended.

tpm2-totp -N 0x01800001 -P - init
tpm2-totp -N 0x01800001 show
tpm2-totp -N 0x01800001 -P - recover
tpm2-totp -N 0x01800001 -P - reseal
    

TCTI configuration¶

All commands take the -T option or the TPM2TOTP_TCTI environment variable to specify the TCTI to be used. If the TCTI is not specified explicitly, the default TCTI configured on the system is used. To e.g. use the TPM simulator bound to a given port, use

tpm2-totp -T mssim:port=2321 init