[master] 23f8e3407 ws: Ban direct access to the workspace id

[Dridi Boukelmoune]

commit 23f8e3407d0ce6dc6a411e33d9ba16a079d06302
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Wed May 6 22:58:07 2020 +0200

    ws: Ban direct access to the workspace id
    
    From this point on, only cache_ws.c fiddles with struct ws, which needs
    to remain visible in order to be embeddable in other data structures. We
    have an API covering all use cases in tree, except vmod_vtc operations
    that violate the contract to provide a rudimentary dump in VCL for test
    purposes.
    
    Inline functions provided in headers aren't considered a problem here.

diff --git a/bin/varnishd/cache/cache.h b/bin/varnishd/cache/cache.h
index fb8e11f0b..b3ae30c99 100644
--- a/bin/varnishd/cache/cache.h
+++ b/bin/varnishd/cache/cache.h
@@ -136,10 +136,12 @@ struct lock { void *priv; };	// Opaque
  * Workspace structure for quick memory allocation.
  */
 
+#define WS_ID_SIZE 4
+
 struct ws {
 	unsigned		magic;
 #define WS_MAGIC		0x35fac554
-	char			id[4];		/* identity */
+	char			id[WS_ID_SIZE];	/* identity */
 	char			*s;		/* (S)tart of buffer */
 	char			*f;		/* (F)ree/front pointer */
 	char			*r;		/* (R)eserved length */
@@ -793,6 +795,7 @@ int WS_Overflowed(const struct ws *ws);
 const char *WS_Printf(struct ws *ws, const char *fmt, ...) v_printflike_(2, 3);
 int WS_Inside(const struct ws *, const void *, const void *);
 void WS_Assert_Allocated(const struct ws *ws, const void *ptr, ssize_t len);
+void WS_Id(const struct ws *ws, char *id);
 
 void WS_VSB_new(struct vsb *, struct ws *);
 char *WS_VSB_finish(struct vsb *, struct ws *, size_t *);
diff --git a/bin/varnishd/cache/cache_http.c b/bin/varnishd/cache/cache_http.c
index 1c608ff3a..9fa4c1f64 100644
--- a/bin/varnishd/cache/cache_http.c
+++ b/bin/varnishd/cache/cache_http.c
@@ -112,10 +112,11 @@ http_VSL_log(const struct http *hp)
 static void
 http_fail(const struct http *hp)
 {
+	char id[WS_ID_SIZE];
 
 	VSC_C_main->losthdr++;
-	hp->ws->id[0] |= 0x20;		// cheesy tolower()
-	VSLb(hp->vsl, SLT_Error, "out of workspace (%s)", hp->ws->id);
+	WS_Id(hp->ws, id);
+	VSLb(hp->vsl, SLT_Error, "out of workspace (%s)", id);
 	WS_MarkOverflow(hp->ws);
 }
 
diff --git a/bin/varnishd/cache/cache_ws.c b/bin/varnishd/cache/cache_ws.c
index b4dc26435..c8fb32210 100644
--- a/bin/varnishd/cache/cache_ws.c
+++ b/bin/varnishd/cache/cache_ws.c
@@ -114,6 +114,16 @@ WS_Init(struct ws *ws, const char *id, void *space, unsigned len)
 	WS_Assert(ws);
 }
 
+void
+WS_Id(const struct ws *ws, char *id)
+{
+
+	WS_Assert(ws);
+	AN(id);
+	memcpy(id, ws->id, WS_ID_SIZE);
+	id[0] |= 0x20;			// cheesy tolower()
+}
+
 void
 WS_MarkOverflow(struct ws *ws)
 {