http://bitcointrezor.com/

1. Install Docker (from docker.com or from your distribution repositories)
2. git clone https://github.com/trezor/trezor-mcu.git
3. cd trezor-mcu
4. ./firmware-docker-build.sh

This creates trezor.bin in current directory and prints its fingerprint at the last line of the build log.

1. Pick version of firmware binary listed on https://mytrezor.com/data/firmware/releases.json
2. Download it: wget -O trezor.signed.bin.hex https://mytrezor.com/data/firmware/trezor-1.1.0.bin.hex
3. xxd -r -p trezor.signed.bin.hex trezor.signed.bin
4. ./firmware-fingerprint.sh trezor.signed.bin

Step 4 should produce the same sha256 fingerprint like your local build.

The reasoning for firmware-fingerprint.sh script is that signed firmware has special header holding signatures themselves, which must be avoided while calculating the fingerprint.