1 files changed, 128 insertions, 23 deletions

diff --git a/lib9p/srv.c b/lib9p/srv.c
index 9d1b4ed..8940afe 100644
--- a/lib9p/srv.c
+++ b/lib9p/srv.c
@@ -365,12 +365,39 @@ static void handle_message(struct _lib9p_srv_req *ctx) {
 	}
 }
 
+#define handler_common(ctx, req, resp) do { \
+		assert(ctx);                \
+		assert(req);                \
+		assert(resp);               \
+		resp->tag = req->tag;       \
+	} while (0)
+
+static inline bool check_perm(struct lib9p_srv_ctx *ctx, struct lib9p_stat *stat, uint8_t action) {
+	assert(ctx);
+	assert(stat);
+	assert(action);
+
+	/* TODO actually check user and group instead of just assuming "other".  */
+	uint8_t mode = (uint8_t)(stat->file_mode & 07);
+
+	return mode & action;
+}
+
+static inline bool release(struct lib9p_srv_ctx *ctx, struct lib9p_srv_file *file) {
+	assert(file);
+	file->_refcount--;
+	if (file->_refcount == 0) {
+		if (file->_parent_dir != file)
+			release(ctx, file->_parent_dir);
+		file->vtable->free(ctx, file);
+	}
+	return lib9p_ctx_has_error(&ctx->basectx);
+}
+
 static void handle_Tversion(struct _lib9p_srv_req *ctx,
                             struct lib9p_msg_Tversion *req,
                             struct lib9p_msg_Rversion *resp) {
-	assert(ctx);
-	assert(req);
-	assert(resp);
+	handler_common(ctx, req, resp);
 
 	enum lib9p_version version = LIB9P_VER_unknown;
 
@@ -440,13 +467,6 @@ static void handle_Tversion(struct _lib9p_srv_req *ctx,
 	ctx->parent_sess->rerror_overhead = min_msg_size;
 }
 
-#define handler_common(ctx, req, resp) do { \
-		assert(ctx);                \
-		assert(req);                \
-		assert(resp);               \
-		resp->tag = req->tag;       \
-	} while (0)
-
 static void handle_Tauth(struct _lib9p_srv_req *ctx,
                          struct lib9p_msg_Tauth *req,
                          struct lib9p_msg_Rauth *resp) {
@@ -522,11 +542,12 @@ static void handle_Tattach(struct _lib9p_srv_req *ctx,
 	if (lib9p_ctx_has_error(&ctx->ctx.basectx))
 		return;
 	rootdir->_parent_dir = rootdir;
+	rootdir->_refcount++;
 
 	if (!fidmap_store(&ctx->parent_sess->fids, req->fid, rootdir)) {
 		lib9p_error(&ctx->ctx.basectx,
 		            LINUX_EMFILE, "too many open files");
-		rootdir->vtable->free(&ctx->ctx, rootdir);
+		release(&ctx->ctx, rootdir);
 		return;
 	}
 
@@ -546,7 +567,7 @@ static void handle_Tattach(struct _lib9p_srv_req *ctx,
 static void handle_Tflush(struct _lib9p_srv_req *ctx,
                           struct lib9p_msg_Tflush *req,
                           struct lib9p_msg_Rflush *resp) {
-	handler_common(ctx, req, resp);;
+	handler_common(ctx, req, resp);
 
 	lib9p_error(&ctx->ctx.basectx,
 	            LINUX_EOPNOTSUPP, "flush not yet implemented");
@@ -577,6 +598,7 @@ static void handle_Twalk(struct _lib9p_srv_req *ctx,
 		assert((dirp == NULL) == lib9p_ctx_has_error(&ctx->ctx.basectx));
 		if (lib9p_ctx_has_error(&ctx->ctx.basectx))
 			return;
+		dirp->_refcount++; /* ref-A: presumptive insertion into fidmap */
 	}
 
 	resp->wqid = (struct lib9p_qid *)(&resp[1]);
@@ -588,7 +610,9 @@ static void handle_Twalk(struct _lib9p_srv_req *ctx,
 			struct lib9p_stat stat = dirp->vtable->stat(&ctx->ctx, dirp);
 			if (lib9p_ctx_has_error(&ctx->ctx.basectx))
 				break;
-			if (!(stat.file_qid.type & LIB9P_QT_DIR) || !(stat.file_mode & LIB9P_DM_DIR)) {
+			assert( ((bool)(stat.file_qid.type & LIB9P_QT_DIR)) ==
+			        ((bool)(stat.file_mode & LIB9P_DM_DIR)) );
+			if (!(stat.file_mode & LIB9P_DM_DIR)) {
 				lib9p_error(&ctx->ctx.basectx,
 				            LINUX_ENOTDIR, "not a directory");
 				break;
@@ -598,14 +622,27 @@ static void handle_Twalk(struct _lib9p_srv_req *ctx,
 			assert((memberp == NULL) == lib9p_ctx_has_error(&ctx->ctx.basectx));
 			if (lib9p_ctx_has_error(&ctx->ctx.basectx))
 				break;
+			memberp->_parent_dir = dirp;
+			dirp->_refcount++; /* memberp->_parent_dir */
 		}
+		memberp->_refcount++; /* presumptively take ref-A */
 
 		struct lib9p_stat stat = memberp->vtable->stat(&ctx->ctx, memberp);
-		if (lib9p_ctx_has_error(&ctx->ctx.basectx))
+		if (lib9p_ctx_has_error(&ctx->ctx.basectx)) {
+			release(&ctx->ctx, memberp); /* presumption of taking ref-A failed */
+			break;
+		}
+		if (!check_perm(&ctx->ctx, &stat, 0b001)) {
+			lib9p_error(&ctx->ctx.basectx,
+			            LINUX_EACCES, "you do not have execute permission on that directory");
+			release(&ctx->ctx, memberp); /* presumption of taking ref-A failed */
 			break;
+		}
+
 		resp->wqid[resp->nwqid] = stat.file_qid;
 
-		dirp->vtable->free(&ctx->ctx, dirp);
+		/* presumption of taking ref-A succeeded */
+		release(&ctx->ctx, dirp);
 		dirp = memberp;
 	}
 	if (resp->nwqid == req->nwname) {
@@ -615,21 +652,89 @@ static void handle_Twalk(struct _lib9p_srv_req *ctx,
 			if (!fidmap_store(&ctx->parent_sess->fids, req->newfid, dirp)) {
 				lib9p_error(&ctx->ctx.basectx,
 				            LINUX_EMFILE, "too many open files");
-				dirp->vtable->free(&ctx->ctx, dirp);
+				release(&ctx->ctx, dirp); /* presumption of insertion failed */
 			}
-	} else if (resp->nwqid > 0) {
-		ctx->ctx.basectx.err_num = 0;
-		ctx->ctx.basectx.err_msg[0] = '\0';
+	} else {
+		assert(lib9p_ctx_has_error(&ctx->ctx.basectx));
+		if (req->newfid != req->fid)
+			release(&ctx->ctx, dirp); /* presumption of insertion failed */
+		if (resp->nwqid > 0)
+			lib9p_ctx_clear_error(&ctx->ctx.basectx);
 	}
 }
 
 static void handle_Topen(struct _lib9p_srv_req *ctx,
                          struct lib9p_msg_Topen *req,
                          struct lib9p_msg_Ropen *resp) {
-	handler_common(ctx, req, resp);;
+	handler_common(ctx, req, resp);
 
-	lib9p_error(&ctx->ctx.basectx,
-	            LINUX_EOPNOTSUPP, "open not yet implemented");
+	struct lib9p_srv_file **filepp = fidmap_load(&ctx->parent_sess->fids, req->fid);
+	if (!filepp) {
+		lib9p_errorf(&ctx->ctx.basectx,
+		             LINUX_EBADF, "bad file number %"PRIu32, req->fid);
+		return;
+	}
+	struct lib9p_srv_file *filep = *filepp;
+
+	struct lib9p_stat stat = filep->vtable->stat(&ctx->ctx, filep);
+	if (lib9p_ctx_has_error(&ctx->ctx.basectx))
+		return;
+	assert( ((bool)(stat.file_qid.type & LIB9P_QT_DIR)) ==
+	        ((bool)(stat.file_mode & LIB9P_DM_DIR)) );
+
+	lib9p_o_t flags = req->mode;
+	if (stat.file_mode & LIB9P_DM_DIR) {
+		if ( ((flags & LIB9P_O_MODE_MASK) != LIB9P_O_READ) ||
+		     (flags & LIB9P_O_TRUNC) ||
+		     (flags & LIB9P_O_RCLOSE) ) {
+			lib9p_error(&ctx->ctx.basectx,
+			            LINUX_EISDIR, "directories cannot be written, executed, truncated, or removed-on-close");
+			return;
+		}
+	} else {
+		if (stat.file_mode & LIB9P_QT_APPEND)
+			flags = flags & ~LIB9P_O_TRUNC;
+	}
+	if (flags & LIB9P_O_RCLOSE) {
+		struct lib9p_stat parent_stat = filep->_parent_dir->vtable->stat(&ctx->ctx, filep->_parent_dir);
+		if (lib9p_ctx_has_error(&ctx->ctx.basectx))
+			return;
+		if (!check_perm(&ctx->ctx, &parent_stat, 0b010)) {
+			lib9p_error(&ctx->ctx.basectx,
+			            LINUX_EACCES, "permission denied to remove-on-close");
+			return;
+		}
+	}
+	uint8_t perm_bits = 0;
+	switch (flags & LIB9P_O_MODE_MASK) {
+	case LIB9P_O_READ:
+		perm_bits = 0b100;
+		break;
+	case LIB9P_O_WRITE:
+		perm_bits = 0b010;
+		break;
+	case LIB9P_O_RDWR:
+		perm_bits = 0b110;
+		break;
+	case LIB9P_O_EXEC:
+		perm_bits = 0b001;
+		break;
+	}
+	if (!check_perm(&ctx->ctx, &stat, perm_bits)) {
+		lib9p_error(&ctx->ctx.basectx,
+		            LINUX_EACCES, "permission denied");
+	}
+
+	uint32_t iounit = filep->vtable->io(&ctx->ctx, filep, flags);
+	if (lib9p_ctx_has_error(&ctx->ctx.basectx))
+		return;
+
+	filep->_io_flags = flags;
+	filep->_io_unit = iounit;
+	filep->_io_qid = stat.file_qid;
+
+	resp->qid = filep->_io_qid;
+	resp->iounit = filep->_io_unit;
 }
 
 static void handle_Tcreate(struct _lib9p_srv_req *ctx,
@@ -702,7 +807,7 @@ static void handle_Tstat(struct _lib9p_srv_req *ctx,
 static void handle_Twstat(struct _lib9p_srv_req *ctx,
                           struct lib9p_msg_Twstat *req,
                           struct lib9p_msg_Rwstat *resp) {
-	handler_common(ctx, req, resp);;
+	handler_common(ctx, req, resp);
 
 	lib9p_error(&ctx->ctx.basectx,
 	            LINUX_EOPNOTSUPP, "wstat not yet implemented");