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curve25519: Use mbedTLS curve25519 for ECDH, if available

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Signed-off-by: Praneeth Sarode <praneethsarode@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
This commit is contained in:
Praneeth Sarode
2025-03-21 00:08:17 +05:30
committed by Jakub Jelen
parent 84d02e7440
commit 49a355c272
4 changed files with 249 additions and 1 deletions
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225
src/curve25519.c
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@@ -41,6 +41,10 @@
#ifdef HAVE_LIBCRYPTO
#include <openssl/err.h>
#elif defined(HAVE_MBEDTLS_CURVE25519)
#include "mbedcrypto-compat.h"
#include <mbedtls/ecdh.h>
#include <mbedtls/error.h>
#endif
static SSH_PACKET_CALLBACK(ssh_packet_client_curve25519_reply);
@@ -108,6 +112,102 @@ int ssh_curve25519_init(ssh_session session)
session->next_crypto->curve25519_privkey = pkey;
pkey = NULL;
#elif defined(HAVE_MBEDTLS_CURVE25519)
mbedtls_ecdh_context ecdh_ctx;
mbedtls_ctr_drbg_context *ctr_drbg = NULL;
ssh_curve25519_pubkey *pubkey_loc = NULL;
char error_buf[128];
int ret = SSH_ERROR;
ctr_drbg = ssh_get_mbedtls_ctr_drbg_context();
mbedtls_ecdh_init(&ecdh_ctx);
rc = mbedtls_ecdh_setup(&ecdh_ctx, MBEDTLS_ECP_DP_CURVE25519);
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE, "Failed to setup X25519 context: %s", error_buf);
goto error;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_ecdh_gen_public(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(grp),
&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(d),
&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(Q),
mbedtls_ctr_drbg_random,
ctr_drbg);
#else
rc = mbedtls_ecdh_gen_public(&ecdh_ctx.grp,
&ecdh_ctx.d,
&ecdh_ctx.Q,
mbedtls_ctr_drbg_random,
ctr_drbg);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE,
"Failed to generate X25519 keypair: %s",
error_buf);
goto error;
}
if (session->server) {
pubkey_loc = &session->next_crypto->curve25519_server_pubkey;
} else {
pubkey_loc = &session->next_crypto->curve25519_client_pubkey;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_mpi_write_binary_le(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(d),
session->next_crypto->curve25519_privkey,
CURVE25519_PRIVKEY_SIZE);
#else
rc = mbedtls_mpi_write_binary_le(&ecdh_ctx.d,
session->next_crypto->curve25519_privkey,
CURVE25519_PRIVKEY_SIZE);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE,
"Failed to write X25519 private key: %s",
error_buf);
goto error;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_mpi_write_binary_le(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(Q)
.MBEDTLS_PRIVATE(X),
*pubkey_loc,
CURVE25519_PUBKEY_SIZE);
#else
rc = mbedtls_mpi_write_binary_le(&ecdh_ctx.Q.X,
*pubkey_loc,
CURVE25519_PUBKEY_SIZE);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE,
"Failed to write X25519 public key: %s",
error_buf);
goto error;
}
ret = SSH_OK;
error:
mbedtls_ecdh_free(&ecdh_ctx);
return ret;
#else
rc = ssh_get_random(session->next_crypto->curve25519_privkey,
CURVE25519_PRIVKEY_SIZE, 1);
@@ -234,6 +334,131 @@ out:
if (ret == SSH_ERROR) {
return ret;
}
#elif defined(HAVE_MBEDTLS_CURVE25519)
mbedtls_ecdh_context ecdh_ctx;
mbedtls_ctr_drbg_context *ctr_drbg = NULL;
ssh_curve25519_pubkey *peer_pubkey_loc = NULL;
char error_buf[128];
int rc, ret = SSH_ERROR;
ctr_drbg = ssh_get_mbedtls_ctr_drbg_context();
mbedtls_ecdh_init(&ecdh_ctx);
rc = mbedtls_ecdh_setup(&ecdh_ctx, MBEDTLS_ECP_DP_CURVE25519);
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE, "Failed to setup X25519 context: %s", error_buf);
goto error;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_mpi_read_binary_le(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(d),
session->next_crypto->curve25519_privkey,
CURVE25519_PRIVKEY_SIZE);
#else
rc = mbedtls_mpi_read_binary_le(&ecdh_ctx.d,
session->next_crypto->curve25519_privkey,
CURVE25519_PRIVKEY_SIZE);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE, "Failed to read private key: %s", error_buf);
goto error;
}
if (session->server) {
peer_pubkey_loc = &session->next_crypto->curve25519_client_pubkey;
} else {
peer_pubkey_loc = &session->next_crypto->curve25519_server_pubkey;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_mpi_read_binary_le(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(Qp)
.MBEDTLS_PRIVATE(X),
*peer_pubkey_loc,
CURVE25519_PUBKEY_SIZE);
#else
rc = mbedtls_mpi_read_binary_le(&ecdh_ctx.Qp.X,
*peer_pubkey_loc,
CURVE25519_PUBKEY_SIZE);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE, "Failed to read peer public key: %s", error_buf);
goto error;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_mpi_lset(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(Qp)
.MBEDTLS_PRIVATE(Z),
1);
#else
rc = mbedtls_mpi_lset(&ecdh_ctx.Qp.Z, 1);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE, "Failed to set Z coordinate: %s", error_buf);
goto error;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_ecdh_compute_shared(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(grp),
&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(z),
&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(Qp),
&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(d),
mbedtls_ctr_drbg_random,
ctr_drbg);
#else
rc = mbedtls_ecdh_compute_shared(&ecdh_ctx.grp,
&ecdh_ctx.z,
&ecdh_ctx.Qp,
&ecdh_ctx.d,
mbedtls_ctr_drbg_random,
ctr_drbg);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE,
"Failed to compute shared secret: %s",
error_buf);
goto error;
}
#if MBEDTLS_VERSION_MAJOR > 2
rc = mbedtls_mpi_write_binary_le(&ecdh_ctx.MBEDTLS_PRIVATE(ctx)
.MBEDTLS_PRIVATE(mbed_ecdh)
.MBEDTLS_PRIVATE(z),
k,
CURVE25519_PUBKEY_SIZE);
#else
rc = mbedtls_mpi_write_binary_le(&ecdh_ctx.z, k, CURVE25519_PUBKEY_SIZE);
#endif
if (rc != 0) {
mbedtls_strerror(rc, error_buf, sizeof(error_buf));
SSH_LOG(SSH_LOG_TRACE, "Failed to write shared secret: %s", error_buf);
goto error;
}
ret = SSH_OK;
error:
mbedtls_ecdh_free(&ecdh_ctx);
return ret;
#else
if (session->server) {
crypto_scalarmult(k, session->next_crypto->curve25519_privkey,