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make tcp server more timing resistant #9

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57 changes: 37 additions & 20 deletions tcp_comm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@ struct tcp_comm_ctx {
// Note: sizeof(buf) is used elsewhere, so if this is changed to not
// be an array, those will need updating
uint8_t buf[(sizeof(uint32_t) * (1 + COMM_MAX_NARG)) + TCP_COMM_MAX_DATA_LEN];
uint32_t args[COMM_MAX_NARG];

uint16_t rx_start_offs;
uint16_t rx_bytes_received;
Expand Down Expand Up @@ -95,6 +96,7 @@ static int tcp_comm_data_complete(struct tcp_comm_ctx *ctx);
static int tcp_comm_response_begin(struct tcp_comm_ctx *ctx);
static int tcp_comm_response_complete(struct tcp_comm_ctx *ctx);
static int tcp_comm_error_begin(struct tcp_comm_ctx *ctx);
static int tcp_comm_handle_input(struct tcp_comm_ctx *ctx);

static int tcp_comm_sync_begin(struct tcp_comm_ctx *ctx)
{
Expand All @@ -119,7 +121,7 @@ static int tcp_comm_opcode_begin(struct tcp_comm_ctx *ctx)
ctx->conn_state = CONN_STATE_READ_OPCODE;
ctx->rx_bytes_needed = sizeof(uint32_t);

return 0;
return tcp_comm_handle_input(ctx);
}

static int tcp_comm_opcode_complete(struct tcp_comm_ctx *ctx)
Expand Down Expand Up @@ -152,14 +154,17 @@ static int tcp_comm_args_complete(struct tcp_comm_ctx *ctx)
const struct comm_command *cmd = ctx->cmd;

uint32_t data_len = 0;
memcpy(ctx->args, ctx->buf, cmd->nargs * sizeof(uint32_t));

if (cmd->size) {
uint32_t status = cmd->size(COMM_BUF_ARGS(ctx->buf),
uint32_t status = cmd->size(ctx->args,
&data_len,
&ctx->resp_data_len);
if (is_error(status)) {
return tcp_comm_error_begin(ctx);
}
} else {
ctx->resp_data_len = 0;
}

return tcp_comm_data_begin(ctx, data_len);
Expand All @@ -182,8 +187,8 @@ static int tcp_comm_data_complete(struct tcp_comm_ctx *ctx)
const struct comm_command *cmd = ctx->cmd;

if (cmd->handle) {
uint32_t status = cmd->handle(COMM_BUF_ARGS(ctx->buf),
COMM_BUF_BODY(ctx->buf, cmd->nargs),
uint32_t status = cmd->handle(ctx->args,
ctx->buf,
COMM_BUF_ARGS(ctx->buf),
COMM_BUF_BODY(ctx->buf, cmd->resp_nargs));
if (is_error(status)) {
Expand Down Expand Up @@ -365,7 +370,32 @@ static err_t tcp_comm_client_sent(void *arg, struct tcp_pcb *tpcb, u16_t len)

return ERR_OK;
}
static int tcp_comm_handle_input(struct tcp_comm_ctx *ctx)
{
while (ctx->rx_bytes_received >= ctx->rx_bytes_needed && ctx->rx_bytes_needed > 0) {
uint16_t consumed = ctx->rx_bytes_needed;

int res = tcp_comm_rx_complete(ctx);
if (res == -2 ) {
return ERR_OK;
}
if (res) {
return tcp_comm_client_complete(ctx, ERR_ARG);
}

ctx->rx_start_offs += consumed;
ctx->rx_bytes_received -= consumed;

if (ctx->rx_bytes_received == 0) {
ctx->rx_start_offs = 0;
break;
}else{
memmove(ctx->buf, ctx->buf + ctx->rx_start_offs,ctx->rx_bytes_received);
ctx->rx_start_offs = 0;
}
}
return ERR_OK;
}
static err_t tcp_comm_client_recv(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err)
{
struct tcp_comm_ctx *ctx = (struct tcp_comm_ctx *)arg;
Expand Down Expand Up @@ -412,22 +442,9 @@ static err_t tcp_comm_client_recv(void *arg, struct tcp_pcb *tpcb, struct pbuf *

ctx->rx_bytes_received += p->tot_len;
tcp_recved(tpcb, p->tot_len);

while (ctx->rx_bytes_received >= ctx->rx_bytes_needed) {
uint16_t consumed = ctx->rx_bytes_needed;

int res = tcp_comm_rx_complete(ctx);
if (res) {
return tcp_comm_client_complete(ctx, ERR_ARG);
}

ctx->rx_start_offs += consumed;
ctx->rx_bytes_received -= consumed;

if (ctx->rx_bytes_received == 0) {
ctx->rx_start_offs = 0;
break;
}
err_t err = tcp_comm_handle_input(ctx);
if(err != ERR_OK) {
return err;
}
}
pbuf_free(p);
Expand Down