sha256sum for Windows

The built-in certutil utility in CMD is not ideal for use in a Dockerfile, primarily because it prints out multiple lines and lacks a -c option for file verification. To avoid relying on third-party solutions from unknown authors, I've created my own sha256sum.exe utility.

Requirements

The Makefile is designed for use with MSVC. Specifically, I've developed it using VS 2022 version v17.7.4.

Building sha256sum.exe

1. Open the x64 Native Tools Command Prompt for VS 2022.
2. Navigate to the folder containing the Makefile.
3. Run the msbuild command.

Alternatively, you can open the Solution file in the Visual Studio IDE.

Usage

sha256sum [OPTION]... [FILE]...

Option	Description
-c, --check	read checksums from the FILE and check them, input must be UTF-8 encoded
-b, --binary	read in binary mode, this is default
-t, --text	read in text mode, fails because WinAPI's ReadFile/CreateFile only reads in binary mode
-q, --quiet	don't print OK, just FAILED if checks fail
-s, --status	don't print anything, just return status code
-w, --warn	shows SHA256SUMS errors
-v, --version	shows program's version

Examples

Here's how to use the utility:

sha256sum.exe myText.txt
sha256sum.exe *.txt
sha256sum.exe hello.txt world.txt
sha256sum.exe *.txt > SHA256SUMS
sha256sum.exe -c SHA256SUMS

Exit Codes

Code	Name	Description
1	MAIN_FAILED_TO_FIND_FILES	WinAPI's FindFirstFile was not able to find files wth given FILE arguments
2	PARSE_ARGS_MISSING_PARAMETER	too few arguments, at least 1 is required
3	PARSE_ARGS_MISSING_SHASUMS_FILE	-c argument found but missing following sum file, -c <FILE>
4	PARSE_ARGS_ALLOCATE_ERROR	memory allocation failed for file list, memory low?
5	CALC_HASH_FAILED_TO_OPEN_FILE	failed to open FILE, check permissions, if file exists
6	CALC_HASH_FAILED_TO_OPEN_ALG_HANDLE	failed to open algorithm handle[1]
7	CALC_HASH_FAILED_TO_ALLOCATE_HASH_BUFFER_SIZE	failed to calculate hash buffer size[1]
8	CALC_HASH_FAILED_TO_ALLOCATE_HASH_OBJECT	failed to allocate hash object[1]
9	CALC_HASH_FAILED_TO_CALC_HASH_LENGTH	failed to calculate hash length[1]
10	CALC_HASH_FAILED_TO_ALLOCATE_HASH_BUFFER	failed to allocate hash buffer[1]
11	CALC_HASH_FAILED_TO_CREATE_HASH	failed to create hash[1]
12	CALC_HASH_FAILED_TO_READ	failed to read from given FILE
13	CALC_HASH_FAILED_TO_HASH	failed to hash[1]
14	CALC_HASH_FAILED_TO_FINISH_HASH	failed to finish hash[1]
15	CALC_HASH_FAILED_TO_ALLOCATE_FILE_HASH	failed to allocate memory for file hash, check your memory
16	PARSE_LINE_INVALID_HASH_TOKEN	invalid hash token may happen if the line does not contain spaces
17	PARSE_LINE_INVALID_HASH_LENGTH	fails when the token is not 64 characters long
18	PARSE_LINE_INAVLID_FILE	fails if the file does not have a second string after the space(s)
19	CHECK_SUMS_FAILED_TO_OPEN_SUM_FILE	failed to open -c FILE
20	CHECK_SUMS_LINE_TOO_LONG	line in sum file is longer exceeds internal buffer (1024)
21	CHECK_SUMS_FAILED_TO_ALLOCATE_WIDE_BUFFER1	line buffer allocation for UTF-16 failed
22	CHECK_SUMS_FAILED_TO_ALLOCATE_FILE_HASH1	file hash object allocation failed
23	CHECK_SUMS_FAILED_TO_ALLOCATE_WIDE_BUFFER2	line buffer allocation for UTF-16 failed[2]
24	CHECK_SUMS_FAILED_TO_ALLOCATE_FILE_HASH2	file hash object allocation failed[2]
25	CHECK_SUMS_FAILED_TO_READ	failed to read from -c FILE
26	CHECK_SUM_CHECKSUM_FAILED	checksum verification failed

[1] This should never occur. sha256sum.exe uses Microsoft's Cryptography API: Next Generation (CNG) with fixed values. If this happens the system is probably missing the CNG.

[2] There is a duplication for parsing the file when the end of file is not reached yet and for the remaining characters that are still in the read buffer.

Design Decisions

I made several decisions regarding the APIs used in the code:

• OpenSSL's EVP Functions: My initial attempt involved using these, but I encountered issues with static linking.
• Go Implementation: Resulted in a larger file size than desired.
• CNG and Windows API: The current implementation uses these native APIs to minimize dependencies and file size.