mirror of
https://git.libssh.org/projects/libssh.git
synced 2025-11-30 13:01:23 +03:00
Clean up code that generates session keys
This patch simply reworks the code to make it more understandable and reduce if() branches. It also avoids reallocs, and instead uses a support buffer to hold intermediate results of the hmac function so that no buffer overrides happen when the requested size is not an exact mutiple of the digest_len. Signed-off-by: Simo Sorce <simo@redhat.com> Reviewed-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com> Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
This commit is contained in:
Simo Sorce
committed by
Andreas Schneider
Andreas Schneider
parent
c235841436
commit
c180211c6b
223
src/kex.c
223
src/kex.c
@@ -1346,17 +1346,15 @@ int ssh_hashbufin_add_cookie(ssh_session session, unsigned char *cookie)
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return 0;
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}
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static int generate_one_key(ssh_string k,
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struct ssh_crypto_struct *crypto,
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unsigned char **output,
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char letter,
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static int generate_one_key(ssh_string k, struct ssh_crypto_struct *crypto,
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unsigned char *output, char letter,
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size_t requested_size)
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{
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ssh_mac_ctx ctx;
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unsigned char *tmp;
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size_t size = crypto->digest_len;
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ctx = ssh_mac_ctx_init(crypto->mac_type);
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unsigned char digest[size];
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ctx = ssh_mac_ctx_init(crypto->mac_type);
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if (ctx == NULL) {
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return -1;
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}
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@@ -1365,25 +1363,27 @@ static int generate_one_key(ssh_string k,
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ssh_mac_update(ctx, crypto->secret_hash, crypto->digest_len);
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ssh_mac_update(ctx, &letter, 1);
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ssh_mac_update(ctx, crypto->session_id, crypto->digest_len);
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ssh_mac_final(*output, ctx);
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ssh_mac_final(digest, ctx);
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if (requested_size < size) {
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size = requested_size;
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}
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memcpy(output, digest, size);
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while (requested_size > size) {
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tmp = realloc(*output, size + crypto->digest_len);
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if (tmp == NULL) {
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return -1;
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}
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*output = tmp;
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ctx = ssh_mac_ctx_init(crypto->mac_type);
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if (ctx == NULL) {
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return -1;
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}
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ssh_mac_update(ctx, k, ssh_string_len(k) + 4);
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ssh_mac_update(ctx,
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crypto->secret_hash,
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crypto->digest_len);
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ssh_mac_update(ctx, tmp, size);
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ssh_mac_final(tmp + size, ctx);
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ssh_mac_update(ctx, crypto->secret_hash, crypto->digest_len);
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ssh_mac_update(ctx, output, size);
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ssh_mac_final(digest, ctx);
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if (requested_size < size + crypto->digest_len) {
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memcpy(output+size, digest, requested_size - size);
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} else {
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memcpy(output+size, digest, crypto->digest_len);
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}
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size += crypto->digest_len;
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}
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@@ -1394,6 +1394,17 @@ int ssh_generate_session_keys(ssh_session session)
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{
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ssh_string k_string = NULL;
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struct ssh_crypto_struct *crypto = session->next_crypto;
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unsigned char *IV_cli_to_srv = NULL;
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unsigned char *IV_srv_to_cli = NULL;
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unsigned char *enckey_cli_to_srv = NULL;
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unsigned char *enckey_srv_to_cli = NULL;
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unsigned char *intkey_cli_to_srv = NULL;
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unsigned char *intkey_srv_to_cli = NULL;
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size_t IV_len = 0;
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size_t enckey_cli_to_srv_len = 0;
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size_t enckey_srv_to_cli_len = 0;
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size_t intkey_cli_to_srv_len = 0;
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size_t intkey_srv_to_cli_len = 0;
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int rc = -1;
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k_string = ssh_make_bignum_string(crypto->k);
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@@ -1402,153 +1413,105 @@ int ssh_generate_session_keys(ssh_session session)
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goto error;
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}
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crypto->encryptIV = malloc(crypto->digest_len);
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crypto->decryptIV = malloc(crypto->digest_len);
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crypto->encryptkey = malloc(crypto->digest_len);
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crypto->decryptkey = malloc(crypto->digest_len);
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crypto->encryptMAC = malloc(crypto->digest_len);
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crypto->decryptMAC = malloc(crypto->digest_len);
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if (crypto->encryptIV == NULL ||
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crypto->decryptIV == NULL ||
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crypto->encryptkey == NULL || crypto->decryptkey == NULL ||
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crypto->encryptMAC == NULL || crypto->decryptMAC == NULL){
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IV_len = crypto->digest_len;
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if (session->client) {
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enckey_cli_to_srv_len = crypto->out_cipher->keysize / 8;
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enckey_srv_to_cli_len = crypto->in_cipher->keysize / 8;
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intkey_cli_to_srv_len = hmac_digest_len(crypto->out_hmac);
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intkey_srv_to_cli_len = hmac_digest_len(crypto->in_hmac);
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} else {
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enckey_cli_to_srv_len = crypto->in_cipher->keysize / 8;
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enckey_srv_to_cli_len = crypto->out_cipher->keysize / 8;
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intkey_cli_to_srv_len = hmac_digest_len(crypto->in_hmac);
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intkey_srv_to_cli_len = hmac_digest_len(crypto->out_hmac);
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}
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IV_cli_to_srv = malloc(IV_len);
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IV_srv_to_cli = malloc(IV_len);
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enckey_cli_to_srv = malloc(enckey_cli_to_srv_len);
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enckey_srv_to_cli = malloc(enckey_srv_to_cli_len);
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intkey_cli_to_srv = malloc(intkey_cli_to_srv_len);
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intkey_srv_to_cli = malloc(intkey_srv_to_cli_len);
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if (IV_cli_to_srv == NULL || IV_srv_to_cli == NULL ||
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enckey_cli_to_srv == NULL || enckey_srv_to_cli == NULL ||
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intkey_cli_to_srv == NULL || intkey_srv_to_cli == NULL) {
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ssh_set_error_oom(session);
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goto error;
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}
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/* IV */
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if (session->client) {
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rc = generate_one_key(k_string,
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crypto,
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&crypto->encryptIV,
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'A',
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crypto->digest_len);
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rc = generate_one_key(k_string, crypto, IV_cli_to_srv, 'A', IV_len);
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if (rc < 0) {
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goto error;
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}
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rc = generate_one_key(k_string,
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crypto,
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&crypto->decryptIV,
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'B',
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crypto->digest_len);
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rc = generate_one_key(k_string, crypto, IV_srv_to_cli, 'B', IV_len);
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if (rc < 0) {
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goto error;
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}
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} else {
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rc = generate_one_key(k_string,
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crypto,
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&crypto->decryptIV,
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'A',
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crypto->digest_len);
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/* Encryption Key */
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rc = generate_one_key(k_string, crypto, enckey_cli_to_srv, 'C',
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enckey_cli_to_srv_len);
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if (rc < 0) {
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goto error;
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}
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rc = generate_one_key(k_string,
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crypto,
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&crypto->encryptIV,
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'B',
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crypto->digest_len);
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rc = generate_one_key(k_string, crypto, enckey_srv_to_cli, 'D',
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enckey_srv_to_cli_len);
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if (rc < 0) {
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goto error;
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}
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}
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if (session->client) {
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rc = generate_one_key(k_string,
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crypto,
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&crypto->encryptkey,
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'C',
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crypto->out_cipher->keysize / 8);
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/* Integrity Key */
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rc = generate_one_key(k_string, crypto, intkey_cli_to_srv, 'E',
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intkey_cli_to_srv_len);
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if (rc < 0) {
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goto error;
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}
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rc = generate_one_key(k_string,
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crypto,
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&crypto->decryptkey,
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'D',
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crypto->in_cipher->keysize / 8);
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rc = generate_one_key(k_string, crypto, intkey_srv_to_cli, 'F',
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intkey_srv_to_cli_len);
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if (rc < 0) {
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goto error;
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}
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} else {
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rc = generate_one_key(k_string,
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crypto,
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&crypto->decryptkey,
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'C',
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crypto->in_cipher->keysize / 8);
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if (rc < 0) {
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goto error;
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}
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rc = generate_one_key(k_string,
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crypto,
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&crypto->encryptkey,
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'D',
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crypto->out_cipher->keysize / 8);
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if (rc < 0) {
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goto error;
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}
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}
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if (session->client) {
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rc = generate_one_key(k_string,
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crypto,
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&crypto->encryptMAC,
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'E',
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hmac_digest_len(crypto->out_hmac));
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if (rc < 0) {
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goto error;
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}
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rc = generate_one_key(k_string,
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crypto,
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&crypto->decryptMAC,
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'F',
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hmac_digest_len(crypto->in_hmac));
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if (rc < 0) {
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goto error;
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}
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crypto->encryptIV = IV_cli_to_srv;
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crypto->decryptIV = IV_srv_to_cli;
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crypto->encryptkey = enckey_cli_to_srv;
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crypto->decryptkey = enckey_srv_to_cli;
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crypto->encryptMAC = intkey_cli_to_srv;
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crypto->decryptMAC = intkey_srv_to_cli;
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} else {
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rc = generate_one_key(k_string,
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crypto,
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&crypto->decryptMAC,
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'E',
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hmac_digest_len(crypto->in_hmac));
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if (rc < 0) {
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goto error;
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}
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rc = generate_one_key(k_string,
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crypto,
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&crypto->encryptMAC,
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'F',
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hmac_digest_len(crypto->out_hmac));
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if (rc < 0) {
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goto error;
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}
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crypto->encryptIV = IV_srv_to_cli;
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crypto->decryptIV = IV_cli_to_srv;
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crypto->encryptkey = enckey_srv_to_cli;
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crypto->decryptkey = enckey_cli_to_srv;
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crypto->encryptMAC = intkey_srv_to_cli;
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crypto->decryptMAC = intkey_cli_to_srv;
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}
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#ifdef DEBUG_CRYPTO
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ssh_print_hexa("Encrypt IV",
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crypto->encryptIV,
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crypto->digest_len);
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ssh_print_hexa("Decrypt IV",
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crypto->decryptIV,
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crypto->digest_len);
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ssh_print_hexa("Encryption key",
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crypto->encryptkey,
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crypto->out_cipher->keysize / 8);
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ssh_print_hexa("Decryption key",
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crypto->decryptkey,
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crypto->in_cipher->keysize / 8);
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ssh_print_hexa("Encryption MAC",
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crypto->encryptMAC,
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hmac_digest_len(crypto->out_hmac));
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ssh_print_hexa("Decryption MAC",
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crypto->decryptMAC,
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hmac_digest_len(crypto->in_hmac));
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ssh_print_hexa("Client to Server IV", IV_cli_to_srv, IV_len);
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ssh_print_hexa("Server to Client IV", IV_srv_to_cli, IV_len);
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ssh_print_hexa("Client to Server Encryption Key", enckey_cli_to_srv,
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enckey_cli_to_srv_len);
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ssh_print_hexa("Server to Client Encryption Key", enckey_srv_to_cli,
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enckey_srv_to_cli_len);
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ssh_print_hexa("Client to Server Integrity Key", intkey_cli_to_srv,
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intkey_cli_to_srv_len);
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ssh_print_hexa("Server to Client Integrity Key", intkey_srv_to_cli,
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intkey_srv_to_cli_len);
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#endif
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rc = 0;
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error:
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ssh_string_burn(k_string);
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ssh_string_free(k_string);
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if (rc != 0) {
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free(IV_cli_to_srv);
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free(IV_srv_to_cli);
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free(enckey_cli_to_srv);
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free(enckey_srv_to_cli);
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free(intkey_cli_to_srv);
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free(intkey_srv_to_cli);
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}
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return rc;
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}
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