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Turn SSH-2 MACs into a classoid.

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This piece of tidying-up has come out particularly well in terms of
saving tedious repetition and boilerplate. I've managed to remove
three pointless methods from every MAC implementation by means of
writing them once centrally in terms of the implementation-specific
methods; another method (hmacmd5_sink) vanished because I was able to
make the interface type 'ssh2_mac' be directly usable as a BinarySink
by way of a new delegation system; and because all the method
implementations can now find their own vtable, I was even able to
merge a lot of keying and output functions that had previously
differed only in length parameters by having them look up the lengths
in whatever vtable they were passed.
This commit is contained in:
Simon Tatham
2018-09-13 16:15:17 +01:00
parent 229af2b5bf
commit 853bd8b284
12 changed files with 294 additions and 397 deletions
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95
sshccp.c
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@ -866,27 +866,32 @@ struct ccp_context {
struct poly1305 mac;
BinarySink_IMPLEMENTATION;
ssh2_cipher vt;
ssh2_cipher cvt;
ssh2_mac mac_if;
};
static void *poly_make_context(ssh2_cipher *cipher)
static ssh2_mac *poly_ssh2_new(
const struct ssh2_macalg *alg, ssh2_cipher *cipher)
{
return FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
ctx->mac_if.vt = alg;
BinarySink_DELEGATE_INIT(&ctx->mac_if, ctx);
return &ctx->mac_if;
}
static void poly_free_context(void *ctx)
static void poly_ssh2_free(ssh2_mac *mac)
{
/* Not allocated, just forwarded, no need to free */
}
static void poly_setkey(void *ctx, const void *key)
static void poly_setkey(ssh2_mac *mac, const void *key)
{
/* Uses the same context as ChaCha20, so ignore */
}
static void poly_start(void *handle)
static void poly_start(ssh2_mac *mac)
{
struct ccp_context *ctx = (struct ccp_context *)handle;
struct ccp_context *ctx = FROMFIELD(mac, struct ccp_context, mac_if);
ctx->mac_initialised = 0;
memset(ctx->mac_iv, 0, 8);
@ -926,63 +931,15 @@ static void poly_BinarySink_write(BinarySink *bs, const void *blkv, size_t len)
}
}
static BinarySink *poly_sink(void *handle)
static void poly_genresult(ssh2_mac *mac, unsigned char *blk)
{
struct ccp_context *ctx = (struct ccp_context *)handle;
return BinarySink_UPCAST(ctx);
}
static void poly_genresult(void *handle, unsigned char *blk)
{
struct ccp_context *ctx = (struct ccp_context *)handle;
struct ccp_context *ctx = FROMFIELD(mac, struct ccp_context, mac_if);
poly1305_finalise(&ctx->mac, blk);
}
static int poly_verresult(void *handle, unsigned char const *blk)
{
struct ccp_context *ctx = (struct ccp_context *)handle;
int res;
unsigned char mac[16];
poly1305_finalise(&ctx->mac, mac);
res = smemeq(blk, mac, 16);
return res;
}
/* The generic poly operation used before generate and verify */
static void poly_op(void *handle, const unsigned char *blk, int len,
unsigned long seq)
{
struct ccp_context *ctx = (struct ccp_context *)handle;
poly_start(ctx);
/* the data receiver expects the first 4 bytes to be the IV */
put_uint32(ctx, seq);
put_data(ctx, blk, len);
}
static void poly_generate(void *handle, void *vblk, int len, unsigned long seq)
{
unsigned char *blk = (unsigned char *)vblk;
poly_op(handle, blk, len, seq);
poly_genresult(handle, blk+len);
}
static int poly_verify(void *handle, const void *vblk, int len,
unsigned long seq)
{
const unsigned char *blk = (const unsigned char *)vblk;
poly_op(handle, blk, len, seq);
return poly_verresult(handle, blk+len);
}
static const struct ssh_mac ssh2_poly1305 = {
poly_make_context, poly_free_context,
poly_setkey,
/* whole-packet operations */
poly_generate, poly_verify,
/* partial-packet operations */
poly_start, poly_sink, poly_genresult, poly_verresult,
static const struct ssh2_macalg ssh2_poly1305 = {
poly_ssh2_new, poly_ssh2_free, poly_setkey,
poly_start, poly_genresult,
"", "", /* Not selectable individually, just part of ChaCha20-Poly1305 */
16, 0, "Poly1305"
@ -993,13 +950,13 @@ static ssh2_cipher *ccp_new(const struct ssh2_cipheralg *alg)
struct ccp_context *ctx = snew(struct ccp_context);
BinarySink_INIT(ctx, poly_BinarySink_write);
poly1305_init(&ctx->mac);
ctx->vt = alg;
return &ctx->vt;
ctx->cvt = alg;
return &ctx->cvt;
}
static void ccp_free(ssh2_cipher *cipher)
{
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
smemclr(&ctx->a_cipher, sizeof(ctx->a_cipher));
smemclr(&ctx->b_cipher, sizeof(ctx->b_cipher));
smemclr(&ctx->mac, sizeof(ctx->mac));
@ -1008,14 +965,14 @@ static void ccp_free(ssh2_cipher *cipher)
static void ccp_iv(ssh2_cipher *cipher, const void *iv)
{
/* struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt); */
/* struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt); */
/* IV is set based on the sequence number */
}
static void ccp_key(ssh2_cipher *cipher, const void *vkey)
{
const unsigned char *key = (const unsigned char *)vkey;
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
/* Initialise the a_cipher (for decrypting lengths) with the first 256 bits */
chacha20_key(&ctx->a_cipher, key + 32);
/* Initialise the b_cipher (for content and MAC) with the second 256 bits */
@ -1024,13 +981,13 @@ static void ccp_key(ssh2_cipher *cipher, const void *vkey)
static void ccp_encrypt(ssh2_cipher *cipher, void *blk, int len)
{
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
chacha20_encrypt(&ctx->b_cipher, blk, len);
}
static void ccp_decrypt(ssh2_cipher *cipher, void *blk, int len)
{
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
chacha20_decrypt(&ctx->b_cipher, blk, len);
}
@ -1054,7 +1011,7 @@ static void ccp_length_op(struct ccp_context *ctx, void *blk, int len,
static void ccp_encrypt_length(ssh2_cipher *cipher, void *blk, int len,
unsigned long seq)
{
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
ccp_length_op(ctx, blk, len, seq);
chacha20_encrypt(&ctx->a_cipher, blk, len);
}
@ -1062,7 +1019,7 @@ static void ccp_encrypt_length(ssh2_cipher *cipher, void *blk, int len,
static void ccp_decrypt_length(ssh2_cipher *cipher, void *blk, int len,
unsigned long seq)
{
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, vt);
struct ccp_context *ctx = FROMFIELD(cipher, struct ccp_context, cvt);
ccp_length_op(ctx, blk, len, seq);
chacha20_decrypt(&ctx->a_cipher, blk, len);
}