From 8109b957b668a90d4a9b00f1e9db3d8d7e491bf3 Mon Sep 17 00:00:00 2001 From: Jo-Philipp Wich Date: Wed, 4 Apr 2018 16:58:11 +0200 Subject: [PATCH] file: escape strings in HTML output Escape untrusted input like the request URL or filesystem paths in HTML outputs such as the directory listing or 404 error messages. This fixes certain XSS vulnerabilities which can be leveraged to further exploit the system. Signed-off-by: Jo-Philipp Wich --- file.c | 42 ++++++++++++++++++++++++++++++++++-------- utils.c | 14 +++++++------- 2 files changed, 41 insertions(+), 15 deletions(-) diff --git a/file.c b/file.c index b3702c8..ae9119e 100644 --- a/file.c +++ b/file.c @@ -476,6 +476,7 @@ static void list_entries(struct client *cl, struct dirent **files, int count, const char *type = "directory"; unsigned int mode = S_IXOTH; struct stat s; + char *escaped; char *file; char buf[128]; int i; @@ -501,16 +502,22 @@ static void list_entries(struct client *cl, struct dirent **files, int count, if (!(s.st_mode & mode)) goto next; + escaped = uh_htmlescape(name); + + if (!escaped) + goto next; + uh_chunk_printf(cl, "

%s%s" "
modified: %s" "
%s - %.02f kbyte
" "

", - path, name, suffix, - name, suffix, + path, escaped, suffix, + escaped, suffix, uh_file_unix2date(s.st_mtime, buf, sizeof(buf)), type, s.st_size / 1024.0); + free(escaped); *file = 0; next: free(files[i]); @@ -520,21 +527,29 @@ next: static void uh_file_dirlist(struct client *cl, struct path_info *pi) { struct dirent **files = NULL; + char *escaped_path = uh_htmlescape(pi->name); int count = 0; + if (!escaped_path) + { + uh_client_error(cl, 500, "Internal Server Error", "Out of memory"); + return; + } + uh_file_response_200(cl, NULL); ustream_printf(cl->us, "Content-Type: text/html\r\n\r\n"); uh_chunk_printf(cl, "Index of %s" "

Index of %s

", - pi->name, pi->name); + escaped_path, escaped_path); count = scandir(pi->phys, &files, NULL, dirent_cmp); if (count > 0) { strcpy(uh_buf, pi->phys); - list_entries(cl, files, count, pi->name, uh_buf); + list_entries(cl, files, count, escaped_path, uh_buf); } + free(escaped_path); free(files); uh_chunk_printf(cl, "

"); @@ -613,7 +628,7 @@ static void uh_file_request(struct client *cl, const char *url, { int fd; struct http_request *req = &cl->request; - char *error_handler; + char *error_handler, *escaped_url; if (!(pi->stat.st_mode & S_IROTH)) goto error; @@ -649,9 +664,14 @@ error: return; } + escaped_url = uh_htmlescape(url); + uh_client_error(cl, 403, "Forbidden", "You don't have permission to access %s on this server.", - url); + escaped_url ? escaped_url : "the url"); + + if (escaped_url) + free(escaped_url); } void uh_dispatch_add(struct dispatch_handler *d) @@ -872,7 +892,7 @@ void uh_handle_request(struct client *cl) struct http_request *req = &cl->request; struct dispatch_handler *d; char *url = blobmsg_data(blob_data(cl->hdr.head)); - char *error_handler; + char *error_handler, *escaped_url; blob_buf_init(&cl->hdr_response, 0); url = uh_handle_alias(url); @@ -906,5 +926,11 @@ void uh_handle_request(struct client *cl) return; } - uh_client_error(cl, 404, "Not Found", "The requested URL %s was not found on this server.", url); + escaped_url = uh_htmlescape(url); + + uh_client_error(cl, 404, "Not Found", "The requested URL %s was not found on this server.", + escaped_url ? escaped_url : ""); + + if (escaped_url) + free(escaped_url); } diff --git a/utils.c b/utils.c index 1c61c41..d990d7d 100644 --- a/utils.c +++ b/utils.c @@ -269,11 +269,11 @@ static bool is_html_special_char(char c) char *uh_htmlescape(const char *str) { - size_t len; + size_t i, len; char *p, *copy; - for (p = str, len = 1; *p; p++) - if (is_html_special_char(*p)) + for (i = 0, len = 1; str[i]; i++) + if (is_html_special_char(str[i])) len += 6; /* &#x??; */ else len++; @@ -283,11 +283,11 @@ char *uh_htmlescape(const char *str) if (!copy) return NULL; - for (p = copy; *str; str++) - if (is_html_special_char(*str)) - p += sprintf(p, "&#x%02x;", (unsigned int)*str); + for (i = 0, p = copy; str[i]; i++) + if (is_html_special_char(str[i])) + p += sprintf(p, "&#x%02x;", (unsigned int)str[i]); else - *p++ = *str; + *p++ = str[i]; return copy; } -- 2.25.1