Use the ChaCha-Poly1305 cipher for the SPTPS protocol.

[meshlink] / src / chacha-poly1305 / chacha-poly1305.c

diff --git a/src/chacha-poly1305/chacha-poly1305.c b/src/chacha-poly1305/chacha-poly1305.c
new file mode 100644 (file)
index 0000000..bd5cb2c
--- /dev/null
+++ b/src/chacha-poly1305/chacha-poly1305.c
@@ -0,0 +1,103 @@
+#include "../system.h"
+
+#include "../cipher.h"
+#include "../xalloc.h"
+
+#include "chacha.h"
+#include "chacha-poly1305.h"
+#include "poly1305.h"
+
+struct chacha_poly1305_ctx {
+       struct chacha_ctx main_ctx, header_ctx;
+};
+
+chacha_poly1305_ctx_t *chacha_poly1305_init(void)
+{
+       chacha_poly1305_ctx_t *ctx = xzalloc(sizeof *ctx);
+       return ctx;
+}
+
+void chacha_poly1305_exit(chacha_poly1305_ctx_t *ctx)
+{
+       free(ctx);
+}
+
+bool chacha_poly1305_set_key(chacha_poly1305_ctx_t *ctx, const void *key)
+{
+       chacha_keysetup(&ctx->main_ctx, key, 256);
+       chacha_keysetup(&ctx->header_ctx, key + 32, 256);
+       return true;
+}
+
+static void put_u64(void *vp, uint64_t v)
+{
+       uint8_t *p = (uint8_t *) vp;
+
+       p[0] = (uint8_t) (v >> 56) & 0xff;
+       p[1] = (uint8_t) (v >> 48) & 0xff;
+       p[2] = (uint8_t) (v >> 40) & 0xff;
+       p[3] = (uint8_t) (v >> 32) & 0xff;
+       p[4] = (uint8_t) (v >> 24) & 0xff;
+       p[5] = (uint8_t) (v >> 16) & 0xff;
+       p[6] = (uint8_t) (v >> 8) & 0xff;
+       p[7] = (uint8_t) v & 0xff;
+}
+
+bool chacha_poly1305_encrypt(chacha_poly1305_ctx_t *ctx, uint64_t seqnr, const void *indata, size_t inlen, void *outdata, size_t *outlen) {
+       uint8_t seqbuf[8];
+       const uint8_t one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 };      /* NB little-endian */
+       uint8_t poly_key[POLY1305_KEYLEN];
+
+       /*
+        * Run ChaCha20 once to generate the Poly1305 key. The IV is the
+        * packet sequence number.
+        */
+       memset(poly_key, 0, sizeof(poly_key));
+       put_u64(seqbuf, seqnr);
+       chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
+       chacha_encrypt_bytes(&ctx->main_ctx, poly_key, poly_key, sizeof(poly_key));
+
+       /* Set Chacha's block counter to 1 */
+       chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
+
+       chacha_encrypt_bytes(&ctx->main_ctx, indata, outdata, inlen);
+       poly1305_auth(outdata + inlen, outdata, inlen, poly_key);
+
+       if (outlen)
+               *outlen = inlen + POLY1305_TAGLEN;
+
+       return true;
+}
+
+bool chacha_poly1305_decrypt(chacha_poly1305_ctx_t *ctx, uint64_t seqnr, const void *indata, size_t inlen, void *outdata, size_t *outlen) {
+       uint8_t seqbuf[8];
+       const uint8_t one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 };      /* NB little-endian */
+       uint8_t expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];
+
+       /*
+        * Run ChaCha20 once to generate the Poly1305 key. The IV is the
+        * packet sequence number.
+        */
+       memset(poly_key, 0, sizeof(poly_key));
+       put_u64(seqbuf, seqnr);
+       chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
+       chacha_encrypt_bytes(&ctx->main_ctx, poly_key, poly_key, sizeof(poly_key));
+
+       /* Set Chacha's block counter to 1 */
+       chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
+
+       /* Check tag before anything else */
+       inlen -= POLY1305_TAGLEN;
+       const uint8_t *tag = indata + inlen;
+
+       poly1305_auth(expected_tag, indata, inlen, poly_key);
+       if (memcmp(expected_tag, tag, POLY1305_TAGLEN))
+               return false;
+
+       chacha_encrypt_bytes(&ctx->main_ctx, indata, outdata, inlen);
+
+       if (outlen)
+               *outlen = inlen;
+
+       return true;
+}