Check `max-blob-size` before reading, default 10 MB

Only the tree view honoured the limit, and only after loading the
whole object. The raw blob, plain, blame and readme paths now check
the size before reading, and the default moves from unlimited to
10 MB so a fresh install never buffers a huge object whole, with zero
still the opt-out.

5 files changed, 33 insertions, 8 deletions

diff --git a/source/cgit.c b/source/cgit.c
index 8a7027c..d80aebd 100644
--- a/source/cgit.c
+++ b/source/cgit.c
@@ -403,7 +403,7 @@ static void prepare_context(void)
 	ctx.cfg.max_lock_attempts = 5;
 	ctx.cfg.max_msg_len = 80;
 	ctx.cfg.max_repodesc_len = 80;
-	ctx.cfg.max_blob_size = 0;
+	ctx.cfg.max_blob_size = 10 * 1024; /* 10 MB; bounds per-request memory */
 	ctx.cfg.max_stats = 0;
 	ctx.cfg.project_list = NULL;
 	ctx.cfg.renamelimit = -1;
diff --git a/source/ui-blame.c b/source/ui-blame.c
index 1b9df88..99f6de0 100644
--- a/source/ui-blame.c
+++ b/source/ui-blame.c
@@ -127,6 +127,12 @@ static void print_object(const struct object_id *oid, const char *path,
 				      oid_to_hex(oid));
 		return;
 	}
+	if (ctx.cfg.max_blob_size && size / 1024 > (unsigned long)ctx.cfg.max_blob_size) {
+		cgit_print_error_page(413, "Too large",
+			"blob size (%luKB) exceeds display size limit (%dKB)",
+			size / 1024, ctx.cfg.max_blob_size);
+		return;
+	}
 
 	buf = odb_read_object(the_repository->objects, oid, &type, &size);
 	if (!buf) {
diff --git a/source/ui-blob.c b/source/ui-blob.c
index ad84f3d..67c718b 100644
--- a/source/ui-blob.c
+++ b/source/ui-blob.c
@@ -102,6 +102,8 @@ int cgit_print_file(char *path, const char *head, int file_only, int html_escape
 	}
 	if (type == OBJ_BAD)
 		return -1;
+	if (ctx.cfg.max_blob_size && size / 1024 > (unsigned long)ctx.cfg.max_blob_size)
+		return -1;
 	buf = odb_read_object(the_repository->objects, &oid, &type, &size);
 	if (!buf)
 		return -1;
@@ -170,6 +172,14 @@ void cgit_print_blob(const char *hex, char *path, const char *head, int file_onl
 		return;
 	}
 
+	/* Reject an oversized object before reading it whole into memory. */
+	if (ctx.cfg.max_blob_size && size / 1024 > (unsigned long)ctx.cfg.max_blob_size) {
+		cgit_print_error_page(413, "Too large",
+				"Object size (%luKB) exceeds limit (%dKB)",
+				size / 1024, ctx.cfg.max_blob_size);
+		return;
+	}
+
 	buf = odb_read_object(the_repository->objects, &oid, &type, &size);
 	if (!buf) {
 		cgit_print_error_page(500, "Internal server error",
diff --git a/source/ui-plain.c b/source/ui-plain.c
index c041711..8486fa4 100644
--- a/source/ui-plain.c
+++ b/source/ui-plain.c
@@ -30,6 +30,14 @@ static int print_object(const struct object_id *oid, const char *path)
 		return 1;
 	}
 
+	/* Reject an oversized object before reading it whole into memory. */
+	if (ctx.cfg.max_blob_size && size / 1024 > (unsigned long)ctx.cfg.max_blob_size) {
+		cgit_print_error_page(413, "Too large",
+			"Object size (%luKB) exceeds limit (%dKB)",
+			size / 1024, ctx.cfg.max_blob_size);
+		return 1;
+	}
+
 	buf = odb_read_object(the_repository->objects, oid, &type, &size);
 	if (!buf) {
 		cgit_print_error_page(404, "Not found", "Not found");
diff --git a/source/ui-tree.c b/source/ui-tree.c
index 292bfc6..f820f1f 100644
--- a/source/ui-tree.c
+++ b/source/ui-tree.c
@@ -117,6 +117,14 @@ static int print_object(const struct object_id *oid, const char *path, const cha
 		return 0;
 	}
 
+	/* Reject an oversized object before reading it whole into memory. */
+	if (ctx.cfg.max_blob_size && size / 1024 > (unsigned long)ctx.cfg.max_blob_size) {
+		cgit_print_error_page(413, "Too large",
+			"blob size (%luKB) exceeds display size limit (%dKB)",
+			size / 1024, ctx.cfg.max_blob_size);
+		return 0;
+	}
+
 	buf = odb_read_object(the_repository->objects, oid, &type, &size);
 	if (!buf) {
 		cgit_print_error_page(500, "Internal server error",
@@ -138,13 +146,6 @@ static int print_object(const struct object_id *oid, const char *path, const cha
 	}
 	html(")\n");
 
-	if (ctx.cfg.max_blob_size && size / 1024 > ctx.cfg.max_blob_size) {
-		htmlf("<div class='error'>blob size (%ldKB) exceeds display size limit (%dKB).</div>",
-				size / 1024, ctx.cfg.max_blob_size);
-		free(buf);
-		return 1;
-	}
-
 	if (is_binary)
 		print_binary_buffer(buf, size);
 	else