Avoid SEGFAULT on invalid requests

When an unknown page is requested, either on the querystring or via
PATH_INFO, we end up with a null-referencing cgit_cmd. This null-
pointer is then used as argument to the hc() function (which decides
what tab to render as 'active'), but this function failed to check if a
valid cmd was specified and a SEGFAULT would occur. This patch fixes the
issue by introducing a 'fallback-cmd' which specifies what tab to render
as 'active' when no valid cmd is requested.

While at it, we now also keep track of the active repository even if an
invalid cmd was requested since we want to show the error message about
the invalid request in the correct context.

Noticed-by: Robin Redeker <elmex@ta-sa.org>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

2 files changed, 6 insertions, 2 deletions

diff --git a/cgit.c b/cgit.c
index c82587b..6e5215e 100644
--- a/cgit.c
+++ b/cgit.c
@@ -196,193 +196,192 @@ static void prepare_context(struct cgit_context *ctx)
 
 struct refmatch {
 	char *req_ref;
 	char *first_ref;
 	int match;
 };
 
 int find_current_ref(const char *refname, const unsigned char *sha1,
 		     int flags, void *cb_data)
 {
 	struct refmatch *info;
 
 	info = (struct refmatch *)cb_data;
 	if (!strcmp(refname, info->req_ref))
 		info->match = 1;
 	if (!info->first_ref)
 		info->first_ref = xstrdup(refname);
 	return info->match;
 }
 
 char *find_default_branch(struct cgit_repo *repo)
 {
 	struct refmatch info;
 	char *ref;
 
 	info.req_ref = repo->defbranch;
 	info.first_ref = NULL;
 	info.match = 0;
 	for_each_branch_ref(find_current_ref, &info);
 	if (info.match)
 		ref = info.req_ref;
 	else
 		ref = info.first_ref;
 	if (ref)
 		ref = xstrdup(ref);
 	return ref;
 }
 
 static int prepare_repo_cmd(struct cgit_context *ctx)
 {
 	char *tmp;
 	unsigned char sha1[20];
 	int nongit = 0;
 
 	setenv("GIT_DIR", ctx->repo->path, 1);
 	setup_git_directory_gently(&nongit);
 	if (nongit) {
 		ctx->page.title = fmt("%s - %s", ctx->cfg.root_title,
 				      "config error");
 		tmp = fmt("Not a git repository: '%s'", ctx->repo->path);
 		ctx->repo = NULL;
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);
 		cgit_print_error(tmp);
 		cgit_print_docend();
 		return 1;
 	}
 	ctx->page.title = fmt("%s - %s", ctx->repo->name, ctx->repo->desc);
 
 	if (!ctx->qry.head) {
 		ctx->qry.nohead = 1;
 		ctx->qry.head = find_default_branch(ctx->repo);
 		ctx->repo->defbranch = ctx->qry.head;
 	}
 
 	if (!ctx->qry.head) {
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);
 		cgit_print_error("Repository seems to be empty");
 		cgit_print_docend();
 		return 1;
 	}
 
 	if (get_sha1(ctx->qry.head, sha1)) {
 		tmp = xstrdup(ctx->qry.head);
 		ctx->qry.head = ctx->repo->defbranch;
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);
 		cgit_print_error(fmt("Invalid branch: %s", tmp));
 		cgit_print_docend();
 		return 1;
 	}
 	return 0;
 }
 
 static void process_request(void *cbdata)
 {
 	struct cgit_context *ctx = cbdata;
 	struct cgit_cmd *cmd;
 
 	cmd = cgit_get_cmd(ctx);
 	if (!cmd) {
 		ctx->page.title = "cgit error";
-		ctx->repo = NULL;
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);
 		cgit_print_error("Invalid request");
 		cgit_print_docend();
 		return;
 	}
 
 	if (cmd->want_repo && !ctx->repo) {
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);
 		cgit_print_error(fmt("No repository selected"));
 		cgit_print_docend();
 		return;
 	}
 
 	if (ctx->repo && prepare_repo_cmd(ctx))
 		return;
 
 	if (cmd->want_layout) {
 		cgit_print_http_headers(ctx);
 		cgit_print_docstart(ctx);
 		cgit_print_pageheader(ctx);
 	}
 
 	cmd->fn(ctx);
 
 	if (cmd->want_layout)
 		cgit_print_docend();
 }
 
 int cmp_repos(const void *a, const void *b)
 {
 	const struct cgit_repo *ra = a, *rb = b;
 	return strcmp(ra->url, rb->url);
 }
 
 void print_repo(struct cgit_repo *repo)
 {
 	printf("repo.url=%s\n", repo->url);
 	printf("repo.name=%s\n", repo->name);
 	printf("repo.path=%s\n", repo->path);
 	if (repo->owner)
 		printf("repo.owner=%s\n", repo->owner);
 	if (repo->desc)
 		printf("repo.desc=%s\n", repo->desc);
 	if (repo->readme)
 		printf("repo.readme=%s\n", repo->readme);
 	printf("\n");
 }
 
 void print_repolist(struct cgit_repolist *list)
 {
 	int i;
 
 	for(i = 0; i < list->count; i++)
 		print_repo(&list->repos[i]);
 }
 
 
 static void cgit_parse_args(int argc, const char **argv)
 {
 	int i;
 	int scan = 0;
 
 	for (i = 1; i < argc; i++) {
 		if (!strncmp(argv[i], "--cache=", 8)) {
 			ctx.cfg.cache_root = xstrdup(argv[i]+8);
 		}
 		if (!strcmp(argv[i], "--nocache")) {
 			ctx.cfg.nocache = 1;
 		}
 		if (!strncmp(argv[i], "--query=", 8)) {
 			ctx.qry.raw = xstrdup(argv[i]+8);
 		}
 		if (!strncmp(argv[i], "--repo=", 7)) {
 			ctx.qry.repo = xstrdup(argv[i]+7);
 		}
 		if (!strncmp(argv[i], "--page=", 7)) {
 			ctx.qry.page = xstrdup(argv[i]+7);
 		}
 		if (!strncmp(argv[i], "--head=", 7)) {
 			ctx.qry.head = xstrdup(argv[i]+7);
 			ctx.qry.has_symref = 1;
 		}
 		if (!strncmp(argv[i], "--sha1=", 7)) {
 			ctx.qry.sha1 = xstrdup(argv[i]+7);
 			ctx.qry.has_sha1 = 1;
 		}
 		if (!strncmp(argv[i], "--ofs=", 6)) {
 			ctx.qry.ofs = atoi(argv[i]+6);
 		}
 		if (!strncmp(argv[i], "--scan-tree=", 12)) {
 			scan++;
 			scan_tree(argv[i] + 12);
diff --git a/ui-shared.c b/ui-shared.c
index 224e5f3..76cd00d 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -484,201 +484,206 @@ void cgit_print_docstart(struct cgit_context *ctx)
 				       fmt("h=%s", ctx->qry.head)));
 		html("' type='application/atom+xml'/>");
 	}
 	html("</head>\n");
 	html("<body>\n");
 }
 
 void cgit_print_docend()
 {
 	html("</div>");
 	if (ctx.cfg.footer)
 		html_include(ctx.cfg.footer);
 	else {
 		htmlf("<div class='footer'>generated  by cgit %s at ",
 			cgit_version);
 		cgit_print_date(time(NULL), FMT_LONGDATE, ctx.cfg.local_time);
 		html("</div>\n");
 	}
 	html("</body>\n</html>\n");
 }
 
 int print_branch_option(const char *refname, const unsigned char *sha1,
 			int flags, void *cb_data)
 {
 	char *name = (char *)refname;
 	html_option(name, name, ctx.qry.head);
 	return 0;
 }
 
 int print_archive_ref(const char *refname, const unsigned char *sha1,
 		       int flags, void *cb_data)
 {
 	struct tag *tag;
 	struct taginfo *info;
 	struct object *obj;
 	char buf[256], *url;
 	unsigned char fileid[20];
 	int *header = (int *)cb_data;
 
 	if (prefixcmp(refname, "refs/archives"))
 		return 0;
 	strncpy(buf, refname+14, sizeof(buf));
 	obj = parse_object(sha1);
 	if (!obj)
 		return 1;
 	if (obj->type == OBJ_TAG) {
 		tag = lookup_tag(sha1);
 		if (!tag || parse_tag(tag) || !(info = cgit_parse_tag(tag)))
 			return 0;
 		hashcpy(fileid, tag->tagged->sha1);
 	} else if (obj->type != OBJ_BLOB) {
 		return 0;
 	} else {
 		hashcpy(fileid, sha1);
 	}
 	if (!*header) {
 		html("<h1>download</h1>\n");
 		*header = 1;
 	}
 	url = cgit_pageurl(ctx.qry.repo, "blob",
 			   fmt("id=%s&amp;path=%s", sha1_to_hex(fileid),
 			       buf));
 	html_link_open(url, NULL, "menu");
 	html_txt(strlpart(buf, 20));
 	html_link_close();
 	return 0;
 }
 
 void add_hidden_formfields(int incl_head, int incl_search, char *page)
 {
 	char *url;
 
 	if (!ctx.cfg.virtual_root) {
 		url = fmt("%s/%s", ctx.qry.repo, page);
 		if (ctx.qry.path)
 			url = fmt("%s/%s", url, ctx.qry.path);
 		html_hidden("url", url);
 	}
 
 	if (incl_head && ctx.qry.head && ctx.repo->defbranch &&
 	    strcmp(ctx.qry.head, ctx.repo->defbranch))
 		html_hidden("h", ctx.qry.head);
 
 	if (ctx.qry.sha1)
 		html_hidden("id", ctx.qry.sha1);
 	if (ctx.qry.sha2)
 		html_hidden("id2", ctx.qry.sha2);
 
 	if (incl_search) {
 		if (ctx.qry.grep)
 			html_hidden("qt", ctx.qry.grep);
 		if (ctx.qry.search)
 			html_hidden("q", ctx.qry.search);
 	}
 }
 
+const char *fallback_cmd = "repolist";
+
 char *hc(struct cgit_cmd *cmd, const char *page)
 {
-	return (strcmp(cmd->name, page) ? NULL : "active");
+	return (strcmp(cmd ? cmd->name : fallback_cmd, page) ? NULL : "active");
 }
 
 void cgit_print_pageheader(struct cgit_context *ctx)
 {
 	struct cgit_cmd *cmd = cgit_get_cmd(ctx);
 
+	if (!cmd && ctx->repo)
+		fallback_cmd = "summary";
+
 	html("<table id='header'>\n");
 	html("<tr>\n");
 	html("<td class='logo' rowspan='2'><a href='");
 	if (ctx->cfg.logo_link)
 		html_attr(ctx->cfg.logo_link);
 	else
 		html_attr(cgit_rooturl());
 	html("'><img src='");
 	html_attr(ctx->cfg.logo);
 	html("' alt='cgit logo'/></a></td>\n");
 
 	html("<td class='main'>");
 	if (ctx->repo) {
 		cgit_index_link("index", NULL, NULL, NULL, 0);
 		html(" : ");
 		cgit_summary_link(ctx->repo->name, ctx->repo->name, NULL, NULL);
 		html("</td><td class='form'>");
 		html("<form method='get' action=''>\n");
 		add_hidden_formfields(0, 1, ctx->qry.page);
 		html("<select name='h' onchange='this.form.submit();'>\n");
 		for_each_branch_ref(print_branch_option, ctx->qry.head);
 		html("</select> ");
 		html("<input type='submit' name='' value='switch'/>");
 		html("</form>");
 	} else
 		html_txt(ctx->cfg.root_title);
 	html("</td></tr>\n");
 
 	html("<tr><td class='sub'>");
 	if (ctx->repo) {
 		html_txt(ctx->repo->desc);
 		html("</td><td class='sub right'>");
 		html_txt(ctx->repo->owner);
 	} else {
 		if (ctx->cfg.root_desc)
 			html_txt(ctx->cfg.root_desc);
 		else if (ctx->cfg.index_info)
 			html_include(ctx->cfg.index_info);
 	}
 	html("</td></tr></table>\n");
 
 	html("<table class='tabs'><tr><td>\n");
 	if (ctx->repo) {
 		cgit_summary_link("summary", NULL, hc(cmd, "summary"),
 				  ctx->qry.head);
 		cgit_refs_link("refs", NULL, hc(cmd, "refs"), ctx->qry.head,
 			       ctx->qry.sha1, NULL);
 		cgit_log_link("log", NULL, hc(cmd, "log"), ctx->qry.head,
 			      NULL, NULL, 0, NULL, NULL);
 		cgit_tree_link("tree", NULL, hc(cmd, "tree"), ctx->qry.head,
 			       ctx->qry.sha1, NULL);
 		cgit_commit_link("commit", NULL, hc(cmd, "commit"),
 				 ctx->qry.head, ctx->qry.sha1);
 		cgit_diff_link("diff", NULL, hc(cmd, "diff"), ctx->qry.head,
 			       ctx->qry.sha1, ctx->qry.sha2, NULL);
 		if (ctx->repo->readme)
 			reporevlink("about", "about", NULL,
 				    hc(cmd, "about"), ctx->qry.head, NULL,
 				    NULL);
 		html("</td><td class='form'>");
 		html("<form class='right' method='get' action='");
 		if (ctx->cfg.virtual_root)
 			html_url_path(cgit_fileurl(ctx->qry.repo, "log",
 						   ctx->qry.path, NULL));
 		html("'>\n");
 		add_hidden_formfields(1, 0, "log");
 		html("<select name='qt'>\n");
 		html_option("grep", "log msg", ctx->qry.grep);
 		html_option("author", "author", ctx->qry.grep);
 		html_option("committer", "committer", ctx->qry.grep);
 		html("</select>\n");
 		html("<input class='txt' type='text' size='10' name='q' value='");
 		html_attr(ctx->qry.search);
 		html("'/>\n");
 		html("<input type='submit' value='search'/>\n");
 		html("</form>\n");
 	} else {
 		site_link(NULL, "index", NULL, hc(cmd, "repolist"), NULL, 0);
 		if (ctx->cfg.root_readme)
 			site_link("about", "about", NULL, hc(cmd, "about"),
 				  NULL, 0);
 		html("</td><td class='form'>");
 		html("<form method='get' action='");
 		html_attr(cgit_rooturl());
 		html("'>\n");
 		html("<input type='text' name='q' size='10' value='");
 		html_attr(ctx->qry.search);
 		html("'/>\n");
 		html("<input type='submit' value='search'/>\n");
 		html("</form>");
 	}
 	html("</td></tr></table>\n");
 	html("<div class='content'>");
 }
 
 void cgit_print_filemode(unsigned short mode)