awstreehash.c

This is a simple, fast and small command line tool to calculate a Amazon AWS Glacier SHA256 Tree Hash. See http://docs.aws.amazon.com/amazonglacier/latest/dev/checksum-calculations.html for the documentation of the hash format. The only dependency is libcrypto from OpenSSL or one of its variants like LibreSSL.

Please note that I wrote this in 2017 where the only way to store data in AWS Glacier was by using the Glacier API. It's now easier to upload data to AWS Glacier because you can (and probably should) use the S3 API now.

Compiling

Just run make.

$ make
rm -f awstreehash
gcc -O3 -pedantic -Wall -o awstreehash awstreehash.c -lcrypto
strip awstreehash

Usage

Usage is identical to sha256sum.

Commandline arguments can be one or more filenames or "-" for stdin. If no commandline arguments are given, stdin is used for input.

reading from stdin

Let's hash the four byte string "test":

$ echo -n test | ./awstreehash
9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08  -

We could also add a dash if we want to read from stdin. This is mainly useful if you want to read from stdin and from some other files simultaneously.

$ echo -n test | ./awstreehash -
9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08  -

reading from file(s)

Let's create an example file which is larger than 1 megabyte.

$ dd if=/dev/zero of=/tmp/test bs=1024 count=2048
2048+0 records in
2048+0 records out
2097152 bytes (2.1 MB, 2.0 MiB) copied, 0.00272925 s, 768 MB/s

We now have a 2 MiB big file which consists of zeros. Let's calculate its AWS glacier hash:

$ ./awstreehash /tmp/test
861890b487038d840e9d71d43bbc0fd4571453fb9d9b1f370caa3582a29b0ec7  test

Because the file is larger than 1MiB, this differs from the sha256sum:

$ sha256sum /tmp/test
5647f05ec18958947d32874eeb788fa396a05d0bab7c1b71f112ceb7e9b31eee  test