rustls: fix partial send handling

When TLS bytes could not completely sent off, the amount of plain bytes
already added to rustls were forgotten. This lead to send those byte
duplicate, corrupting the request send to the server.

Closes #13676

diff --git a/lib/vtls/rustls.c b/lib/vtls/rustls.c
index c4fb432dd71d0ce624feb353f8a4405f07e93a8b..9a7538b62e575b9c029fe566ff6798b6e056c031 100644 (file)
--- a/lib/vtls/rustls.c
+++ b/lib/vtls/rustls.c
@@ -46,7 +46,8 @@ struct rustls_ssl_backend_data
 {
   const struct rustls_client_config *config;
   struct rustls_connection *conn;
-  bool data_pending;
+  size_t plain_out_buffered;
+  BIT(data_in_pending);
 };
 
 /* For a given rustls_result error code, return the best-matching CURLcode. */
@@ -74,7 +75,7 @@ cr_data_pending(struct Curl_cfilter *cf, const struct Curl_easy *data)
   (void)data;
   DEBUGASSERT(ctx && ctx->backend);
   backend = (struct rustls_ssl_backend_data *)ctx->backend;
-  return backend->data_pending;
+  return backend->data_in_pending;
 }
 
 struct io_ctx {
@@ -101,6 +102,8 @@ read_cb(void *userdata, uint8_t *buf, uintptr_t len, uintptr_t *out_n)
   else if(nread == 0)
     connssl->peer_closed = TRUE;
   *out_n = (int)nread;
+  CURL_TRC_CF(io_ctx->data, io_ctx->cf, "cf->next recv(len=%zu) -> %zd, %d",
+              len, nread, result);
   return ret;
 }
 
@@ -120,10 +123,8 @@ write_cb(void *userdata, const uint8_t *buf, uintptr_t len, uintptr_t *out_n)
       ret = EINVAL;
   }
   *out_n = (int)nwritten;
-  /*
-  CURL_TRC_CFX(io_ctx->data, io_ctx->cf, "cf->next send(len=%zu) -> %zd, %d",
-                len, nwritten, result));
-  */
+  CURL_TRC_CF(io_ctx->data, io_ctx->cf, "cf->next send(len=%zu) -> %zd, %d",
+              len, nwritten, result);
   return ret;
 }
 
@@ -165,7 +166,7 @@ static ssize_t tls_recv_more(struct Curl_cfilter *cf,
     return -1;
   }
 
-  backend->data_pending = TRUE;
+  backend->data_in_pending = TRUE;
   *err = CURLE_OK;
   return (ssize_t)tls_bytes_read;
 }
@@ -200,7 +201,7 @@ cr_recv(struct Curl_cfilter *cf, struct Curl_easy *data,
   rconn = backend->conn;
 
   while(plain_bytes_copied < plainlen) {
-    if(!backend->data_pending) {
+    if(!backend->data_in_pending) {
       if(tls_recv_more(cf, data, err) < 0) {
         if(*err != CURLE_AGAIN) {
           nread = -1;
@@ -215,7 +216,7 @@ cr_recv(struct Curl_cfilter *cf, struct Curl_easy *data,
       plainlen - plain_bytes_copied,
       &n);
     if(rresult == RUSTLS_RESULT_PLAINTEXT_EMPTY) {
-      backend->data_pending = FALSE;
+      backend->data_in_pending = FALSE;
     }
     else if(rresult == RUSTLS_RESULT_UNEXPECTED_EOF) {
       failf(data, "rustls: peer closed TCP connection "
@@ -265,6 +266,42 @@ out:
   return nread;
 }
 
+static CURLcode cr_flush_out(struct Curl_cfilter *cf, struct Curl_easy *data,
+                             struct rustls_connection *rconn)
+{
+  struct io_ctx io_ctx;
+  rustls_io_result io_error;
+  size_t tlswritten = 0;
+  size_t tlswritten_total = 0;
+  CURLcode result = CURLE_OK;
+
+  io_ctx.cf = cf;
+  io_ctx.data = data;
+
+  while(rustls_connection_wants_write(rconn)) {
+    io_error = rustls_connection_write_tls(rconn, write_cb, &io_ctx,
+                                           &tlswritten);
+    if(io_error == EAGAIN || io_error == EWOULDBLOCK) {
+      CURL_TRC_CF(data, cf, "cf_send: EAGAIN after %zu bytes",
+                  tlswritten_total);
+      return CURLE_AGAIN;
+    }
+    else if(io_error) {
+      char buffer[STRERROR_LEN];
+      failf(data, "writing to socket: %s",
+            Curl_strerror(io_error, buffer, sizeof(buffer)));
+      return CURLE_SEND_ERROR;
+    }
+    if(tlswritten == 0) {
+      failf(data, "EOF in swrite");
+      return CURLE_SEND_ERROR;
+    }
+    CURL_TRC_CF(data, cf, "cf_send: wrote %zu TLS bytes", tlswritten);
+    tlswritten_total += tlswritten;
+  }
+  return result;
+}
+
 /*
  * On each call:
  *  - Copy `plainlen` bytes into rustls' plaintext input buffer (if > 0).
@@ -283,26 +320,42 @@ cr_send(struct Curl_cfilter *cf, struct Curl_easy *data,
   struct rustls_ssl_backend_data *const backend =
     (struct rustls_ssl_backend_data *)connssl->backend;
   struct rustls_connection *rconn = NULL;
-  struct io_ctx io_ctx;
   size_t plainwritten = 0;
-  size_t tlswritten = 0;
-  size_t tlswritten_total = 0;
   rustls_result rresult;
-  rustls_io_result io_error;
   char errorbuf[256];
   size_t errorlen;
+  const unsigned char *buf = plainbuf;
+  size_t blen = plainlen;
+  ssize_t nwritten = 0;
 
   DEBUGASSERT(backend);
   rconn = backend->conn;
 
-  CURL_TRC_CF(data, cf, "cf_send: %zu plain bytes", plainlen);
-
-  io_ctx.cf = cf;
-  io_ctx.data = data;
+  CURL_TRC_CF(data, cf, "cf_send(len=%zu)", plainlen);
+
+  /* If a previous send blocked, we already added its plain bytes
+   * to rustsls and must not do that again. Flush the TLS bytes and,
+   * if successful, deduct the previous plain bytes from the current
+   * send. */
+  if(backend->plain_out_buffered) {
+    *err = cr_flush_out(cf, data, rconn);
+    CURL_TRC_CF(data, cf, "cf_send: flushing %zu previously added bytes -> %d",
+                backend->plain_out_buffered, *err);
+    if(*err)
+      return -1;
+    if(blen > backend->plain_out_buffered) {
+      blen -= backend->plain_out_buffered;
+      buf += backend->plain_out_buffered;
+    }
+    else
+      blen = 0;
+    nwritten += (ssize_t)backend->plain_out_buffered;
+    backend->plain_out_buffered = 0;
+  }
 
-  if(plainlen > 0) {
-    rresult = rustls_connection_write(rconn, plainbuf, plainlen,
-                                      &plainwritten);
+  if(blen > 0) {
+    CURL_TRC_CF(data, cf, "cf_send: adding %zu plain bytes to rustls", blen);
+    rresult = rustls_connection_write(rconn, buf, blen, &plainwritten);
     if(rresult != RUSTLS_RESULT_OK) {
       rustls_error(rresult, errorbuf, sizeof(errorbuf), &errorlen);
       failf(data, "rustls_connection_write: %.*s", (int)errorlen, errorbuf);
@@ -316,32 +369,27 @@ cr_send(struct Curl_cfilter *cf, struct Curl_easy *data,
     }
   }
 
-  while(rustls_connection_wants_write(rconn)) {
-    io_error = rustls_connection_write_tls(rconn, write_cb, &io_ctx,
-                                           &tlswritten);
-    if(io_error == EAGAIN || io_error == EWOULDBLOCK) {
-      CURL_TRC_CF(data, cf, "cf_send: EAGAIN after %zu bytes",
-                  tlswritten_total);
-      *err = CURLE_AGAIN;
-      return -1;
-    }
-    else if(io_error) {
-      char buffer[STRERROR_LEN];
-      failf(data, "writing to socket: %s",
-            Curl_strerror(io_error, buffer, sizeof(buffer)));
-      *err = CURLE_WRITE_ERROR;
-      return -1;
-    }
-    if(tlswritten == 0) {
-      failf(data, "EOF in swrite");
-      *err = CURLE_WRITE_ERROR;
-      return -1;
+  *err = cr_flush_out(cf, data, rconn);
+  if(*err) {
+    if(CURLE_AGAIN == *err) {
+      /* The TLS bytes may have been partially written, but we fail the
+       * complete send() and remember how much we already added to rustls. */
+      CURL_TRC_CF(data, cf, "cf_send: EAGAIN, remember we added %zu plain"
+                  " bytes already to rustls", blen);
+      backend->plain_out_buffered = plainwritten;
+      if(nwritten) {
+        *err = CURLE_OK;
+        return (ssize_t)nwritten;
+      }
     }
-    CURL_TRC_CF(data, cf, "cf_send: wrote %zu TLS bytes", tlswritten);
-    tlswritten_total += tlswritten;
+    return -1;
   }
+  else
+    nwritten += (ssize_t)plainwritten;
 
-  return plainwritten;
+  CURL_TRC_CF(data, cf, "cf_send(len=%zu) -> %d, %zd",
+              plainlen, *err, nwritten);
+  return nwritten;
 }
 
 /* A server certificate verify callback for rustls that always returns