Refactor the async wait fd logic

Implementation experience has shown that the original plan for async wait
fds was too simplistic. Originally the async logic created a pipe internally
and user/engine code could then get access to it via API calls. It is more
flexible if the engine is able to create its own fd and provide it to the
async code.

Another issue is that there can be a lot of churn in the fd value within
the context of (say) a single SSL connection leading to continually adding
and removing fds from (say) epoll. It is better if we can provide some
stability of the fd value across a whole SSL connection. This is
problematic because an engine has no concept of an SSL connection.

This commit refactors things to introduce an ASYNC_WAIT_CTX which acts as a
proxy for an SSL connection down at the engine layer.

Reviewed-by: Richard Levitte <levitte@openssl.org>

1 files changed, 74 insertions, 3 deletions

diff --git a/engines/e_dasync.c b/engines/e_dasync.c
index cca9f5e3e9..0580103d23 100644
--- a/engines/e_dasync.c
+++ b/engines/e_dasync.c
@@ -61,6 +61,16 @@
 #include <openssl/bn.h>
 #include <openssl/crypto.h>
 
+#if (defined(OPENSSL_SYS_UNIX) || defined(OPENSSL_SYS_CYGWIN)) && defined(OPENSSL_THREADS)
+# undef ASYNC_POSIX
+# define ASYNC_POSIX
+# include <unistd.h>
+#elif defined(_WIN32)
+# undef ASYNC_WIN
+# define ASYNC_WIN
+# include <windows.h>
+#endif
+
 #define DASYNC_LIB_NAME "DASYNC"
 #include "e_dasync_err.c"
 
@@ -261,26 +271,87 @@ static int dasync_digests(ENGINE *e, const EVP_MD **digest,
     return ok;
 }
 
+static void wait_cleanup(ASYNC_WAIT_CTX *ctx, const void *key,
+                         OSSL_ASYNC_FD readfd, void *pvwritefd)
+{
+    OSSL_ASYNC_FD *pwritefd = (OSSL_ASYNC_FD *)pvwritefd;
+#if defined(ASYNC_WIN)
+    CloseHandle(readfd);
+    CloseHandle(*pwritefd);
+#elif defined(ASYNC_POSIX)
+    close(readfd);
+    close(*pwritefd);
+#endif
+    OPENSSL_free(pwritefd);
+}
+
+#define DUMMY_CHAR 'X'
+
 static void dummy_pause_job(void) {
     ASYNC_JOB *job;
+    ASYNC_WAIT_CTX *waitctx;
+    OSSL_ASYNC_FD pipefds[2] = {0, 0};
+    OSSL_ASYNC_FD *writefd;
+#if defined(ASYNC_WIN)
+    DWORD numwritten, numread;
+    char buf = DUMMY_CHAR;
+#elif defined(ASYNC_POSIX)
+    char buf = DUMMY_CHAR;
+#endif
 
     if ((job = ASYNC_get_current_job()) == NULL)
         return;
 
+    waitctx = ASYNC_get_wait_ctx(job);
+
+    if (ASYNC_WAIT_CTX_get_fd(waitctx, engine_dasync_id, &pipefds[0],
+                              (void **)&writefd)) {
+        pipefds[1] = *writefd;
+    } else {
+        writefd = OPENSSL_malloc(sizeof(*writefd));
+        if (writefd == NULL)
+            return;
+#if defined(ASYNC_WIN)
+        if (CreatePipe(&pipefds[0], &pipefds[1], NULL, 256) == 0) {
+            OPENSSL_free(writefd);
+            return;
+        }
+#elif defined(ASYNC_POSIX)
+        if (pipe(pipefds) != 0) {
+            OPENSSL_free(writefd);
+            return;
+        }
+#endif
+        *writefd = pipefds[1];
+
+        if(!ASYNC_WAIT_CTX_set_wait_fd(waitctx, engine_dasync_id, pipefds[0],
+                                       writefd, wait_cleanup)) {
+            wait_cleanup(waitctx, engine_dasync_id, pipefds[0], writefd);
+            return;
+        }
+    }
     /*
      * In the Dummy async engine we are cheating. We signal that the job
      * is complete by waking it before the call to ASYNC_pause_job(). A real
      * async engine would only wake when the job was actually complete
      */
-    ASYNC_wake(job);
+#if defined(ASYNC_WIN)
+    WriteFile(pipefds[1], &buf, 1, &numwritten, NULL);
+#elif defined(ASYNC_POSIX)
+    write(pipefds[1], &buf, 1);
+#endif
 
     /* Ignore errors - we carry on anyway */
     ASYNC_pause_job();
 
-    ASYNC_clear_wake(job);
+    /* Clear the wake signal */
+#if defined(ASYNC_WIN)
+    ReadFile(pipefds[0], &buf, 1, &numread, NULL);
+#elif defined(ASYNC_POSIX)
+    read(pipefds[0], &buf, 1);
+#endif
 }
 
-
 /*
  * SHA1 implementation. At the moment we just defer to the standard
  * implementation