libft_ssl

A C library implementing cryptographic hash functions from scratch.

Each algorithm exposes a uniform streaming API — init / update / final

Algorithms

Algorithm	Digest	Block	Notes
MD5	128-bit	512-bit	RFC 1321 - broken, non-security use only
SHA-256	256-bit	512-bit	SHA-2 family, NSA/NIST - widely used in TLS, Bitcoin
Whirlpool	512-bit	512-bit	ISO/IEC 10118-3 - Miyaguchi-Preneel construction

API

The public interface lives in <libft_ssl/libft_ssl.h>.

struct digest_algo {
    const char  *name;
    size_t       digest_size;   /* bytes */
    size_t       block_size;    /* bytes */
    void (*init)  (void *ctx);
    void (*update)(void *ctx, const uint8_t *data, size_t len);
    void (*final) (void *ctx, uint8_t *out);
};

union digest_ctx { /* one allocation covers all algorithm contexts */
    struct md5_ctx       md5;
    struct sha256_ctx    sha256;
    struct whirlpool_ctx whirlpool;
};

One global instance is provided per algorithm: g_md5, g_sha256, g_whirlpool.

Example

#include <libft_ssl/libft_ssl.h>
#include <stdio.h>

int main(void)
{
    const struct digest_algo *algo = &g_sha256;
    union digest_ctx          ctx;
    uint8_t                   digest[32];

    algo->init(&ctx);
    algo->update(&ctx, (const uint8_t *)"hello", 5);
    algo->final(&ctx, digest);

    for (size_t i = 0; i < algo->digest_size; i++)
        printf("%02x", digest[i]);
    puts("");
}

Compile with:

cc example.c -lft_ssl -o example
# or with pkg-config:
cc example.c $(pkg-config --cflags --libs libft_ssl) -o example

Building

Dependencies

C99 compiler
autoconf
automake
libtool
pdflatex — only if building documentation (--enable-doc)

Steps

./autogen.sh          # generate the build system (first checkout only)
./configure
make
make install          # installs to /usr/local by default

Common configure options:

Flag	Default	Description
`--prefix=PATH`	`/usr/local`	Installation prefix
`--enable-debug`	no	Build with `-g -O0` instead of `-O2`
`--enable-doc`	no	Build PDF documentation (requires `pdflatex`)

pkg-config

After installation the library registers itself with pkg-config:

pkg-config --cflags --libs libft_ssl

Project structure

include/          public and internal headers
src/
  md5/            MD5 init / update / compress / final
  sha256/         SHA-256 init / update / compress / final
  whirlpool/      Whirlpool init / update / compress / final
  libft_ssl.c     algorithm descriptor table (X-macro generated)
doc/              LaTeX source for the technical documentation

Documentation

The full technical write-up is available at https://lohic.dev/libft_ssl.html (PDF).

License

GPLv3 — see LICENSE.

2.9 KiB Raw Blame History