html: properly percent-escape URLs

The only valid characters for a URL are unreserved characters
a-zA-Z0-9_-.~ and the reserved characters !*'();:@&=+$,/?%#[] , as per
RFC 3986.  Everything else must be escaped.  Additionally, the # and
? always have special meaning, and the &, =, and + have special meaning
in a query string, so they too must be escaped.  To make this easier,
a table of escapes is now used so that we do not have to call fmt() for
each character; if the entry is 0, no escaping is needed.

Signed-off-by: Mark Lodato <lodatom@gmail.com>

1 files changed, 32 insertions, 4 deletions

diff --git a/html.c b/html.c
index 4033200..337baeb 100644
--- a/html.c
+++ b/html.c
@@ -1,291 +1,319 @@
 /* html.c: helper functions for html output
  *
  * Copyright (C) 2006 Lars Hjemli
  *
  * Licensed under GNU General Public License v2
  *   (see COPYING for full license text)
  */
 
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
 #include <errno.h>
 
+/* Percent-encoding of each character, except: a-zA-Z0-9!$()*,./:;@- */
+static const char* url_escape_table[256] = {
+        "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07", "%08", "%09",
+        "%0a", "%0b", "%0c", "%0d", "%0e", "%0f", "%10", "%11", "%12", "%13",
+        "%14", "%15", "%16", "%17", "%18", "%19", "%1a", "%1b", "%1c", "%1d",
+        "%1e", "%1f", "%20", 0, "%22", "%23", 0, "%25", "%26", "%27", 0, 0, 0,
+        "%2b", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "%3c", "%3d",
+        "%3e", "%3f", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, "%5c", 0, "%5e", 0, "%60", 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "%7b",
+        "%7c", "%7d", 0, "%7f", "%80", "%81", "%82", "%83", "%84", "%85",
+        "%86", "%87", "%88", "%89", "%8a", "%8b", "%8c", "%8d", "%8e", "%8f",
+        "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97", "%98", "%99",
+        "%9a", "%9b", "%9c", "%9d", "%9e", "%9f", "%a0", "%a1", "%a2", "%a3",
+        "%a4", "%a5", "%a6", "%a7", "%a8", "%a9", "%aa", "%ab", "%ac", "%ad",
+        "%ae", "%af", "%b0", "%b1", "%b2", "%b3", "%b4", "%b5", "%b6", "%b7",
+        "%b8", "%b9", "%ba", "%bb", "%bc", "%bd", "%be", "%bf", "%c0", "%c1",
+        "%c2", "%c3", "%c4", "%c5", "%c6", "%c7", "%c8", "%c9", "%ca", "%cb",
+        "%cc", "%cd", "%ce", "%cf", "%d0", "%d1", "%d2", "%d3", "%d4", "%d5",
+        "%d6", "%d7", "%d8", "%d9", "%da", "%db", "%dc", "%dd", "%de", "%df",
+        "%e0", "%e1", "%e2", "%e3", "%e4", "%e5", "%e6", "%e7", "%e8", "%e9",
+        "%ea", "%eb", "%ec", "%ed", "%ee", "%ef", "%f0", "%f1", "%f2", "%f3",
+        "%f4", "%f5", "%f6", "%f7", "%f8", "%f9", "%fa", "%fb", "%fc", "%fd",
+        "%fe", "%ff"
+};
+
 int htmlfd = STDOUT_FILENO;
 
 char *fmt(const char *format, ...)
 {
         static char buf[8][1024];
         static int bufidx;
         int len;
         va_list args;
 
         bufidx++;
         bufidx &= 7;
 
         va_start(args, format);
         len = vsnprintf(buf[bufidx], sizeof(buf[bufidx]), format, args);
         va_end(args);
         if (len>sizeof(buf[bufidx])) {
                 fprintf(stderr, "[html.c] string truncated: %s\n", format);
                 exit(1);
         }
         return buf[bufidx];
 }
 
 void html_raw(const char *data, size_t size)
 {
         write(htmlfd, data, size);
 }
 
 void html(const char *txt)
 {
         write(htmlfd, txt, strlen(txt));
 }
 
 void htmlf(const char *format, ...)
 {
         static char buf[65536];
         va_list args;
 
         va_start(args, format);
         vsnprintf(buf, sizeof(buf), format, args);
         va_end(args);
         html(buf);
 }
 
 void html_status(int code, const char *msg, int more_headers)
 {
         htmlf("Status: %d %s\n", code, msg);
         if (!more_headers)
                 html("\n");
 }
 
 void html_txt(const char *txt)
 {
         const char *t = txt;
         while(t && *t){
                 int c = *t;
                 if (c=='<' || c=='>' || c=='&') {
                         write(htmlfd, txt, t - txt);
                         if (c=='>')
                                 html("&gt;");
                         else if (c=='<')
                                 html("&lt;");
                         else if (c=='&')
                                 html("&amp;");
                         txt = t+1;
                 }
                 t++;
         }
         if (t!=txt)
                 html(txt);
 }
 
 void html_ntxt(int len, const char *txt)
 {
         const char *t = txt;
         while(t && *t && len--){
                 int c = *t;
                 if (c=='<' || c=='>' || c=='&') {
                         write(htmlfd, txt, t - txt);
                         if (c=='>')
                                 html("&gt;");
                         else if (c=='<')
                                 html("&lt;");
                         else if (c=='&')
                                 html("&amp;");
                         txt = t+1;
                 }
                 t++;
         }
         if (t!=txt)
                 write(htmlfd, txt, t - txt);
         if (len<0)
                 html("...");
 }
 
 void html_attr(const char *txt)
 {
         const char *t = txt;
         while(t && *t){
                 int c = *t;
                 if (c=='<' || c=='>' || c=='\'' || c=='\"') {
                         write(htmlfd, txt, t - txt);
                         if (c=='>')
                                 html("&gt;");
                         else if (c=='<')
                                 html("&lt;");
                         else if (c=='\'')
                                 html("&#x27;");
                         else if (c=='"')
                                 html("&quot;");
                         txt = t+1;
                 }
                 t++;
         }
         if (t!=txt)
                 html(txt);
 }
 
 void html_url_path(const char *txt)
 {
         const char *t = txt;
         while(t && *t){
                 int c = *t;
-                if (c=='"' || c=='#' || c=='\'' || c=='?') {
+                const char *e = url_escape_table[c];
+                if (e && c!='+' && c!='&' && c!='+') {
                         write(htmlfd, txt, t - txt);
-                        write(htmlfd, fmt("%%%2x", c), 3);
+                        write(htmlfd, e, 3);
                         txt = t+1;
                 }
                 t++;
         }
         if (t!=txt)
                 html(txt);
 }
 
 void html_url_arg(const char *txt)
 {
         const char *t = txt;
         while(t && *t){
                 int c = *t;
-                if (c=='"' || c=='#' || c=='%' || c=='&' || c=='\'' || c=='+' || c=='?') {
+                const char *e = url_escape_table[c];
+                if (e) {
                         write(htmlfd, txt, t - txt);
-                        write(htmlfd, fmt("%%%2x", c), 3);
+                        write(htmlfd, e, 3);
                         txt = t+1;
                 }
                 t++;
         }
         if (t!=txt)
                 html(txt);
 }
 
 void html_hidden(const char *name, const char *value)
 {
         html("<input type='hidden' name='");
         html_attr(name);
         html("' value='");
         html_attr(value);
         html("'/>");
 }
 
 void html_option(const char *value, const char *text, const char *selected_value)
 {
         html("<option value='");
         html_attr(value);
         html("'");
         if (selected_value && !strcmp(selected_value, value))
                 html(" selected='selected'");
         html(">");
         html_txt(text);
         html("</option>\n");
 }
 
 void html_link_open(const char *url, const char *title, const char *class)
 {
         html("<a href='");
         html_attr(url);
         if (title) {
                 html("' title='");
                 html_attr(title);
         }
         if (class) {
                 html("' class='");
                 html_attr(class);
         }
         html("'>");
 }
 
 void html_link_close(void)
 {
         html("</a>");
 }
 
 void html_fileperm(unsigned short mode)
 {
         htmlf("%c%c%c", (mode & 4 ? 'r' : '-'),
               (mode & 2 ? 'w' : '-'), (mode & 1 ? 'x' : '-'));
 }
 
 int html_include(const char *filename)
 {
         FILE *f;
         char buf[4096];
         size_t len;
 
         if (!(f = fopen(filename, "r"))) {
                 fprintf(stderr, "[cgit] Failed to include file %s: %s (%d).\n",
                         filename, strerror(errno), errno);
                 return -1;
         }
         while((len = fread(buf, 1, 4096, f)) > 0)
                 write(htmlfd, buf, len);
         fclose(f);
         return 0;
 }
 
 int hextoint(char c)
 {
         if (c >= 'a' && c <= 'f')
                 return 10 + c - 'a';
         else if (c >= 'A' && c <= 'F')
                 return 10 + c - 'A';
         else if (c >= '0' && c <= '9')
                 return c - '0';
         else
                 return -1;
 }
 
 char *convert_query_hexchar(char *txt)
 {
         int d1, d2;
         if (strlen(txt) < 3) {
                 *txt = '\0';
                 return txt-1;
         }
         d1 = hextoint(*(txt+1));
         d2 = hextoint(*(txt+2));
         if (d1<0 || d2<0) {
                 strcpy(txt, txt+3);
                 return txt-1;
         } else {
                 *txt = d1 * 16 + d2;
                 strcpy(txt+1, txt+3);
                 return txt;
         }
 }
 
 int http_parse_querystring(const char *txt_, void (*fn)(const char *name, const char *value))
 {
         char *t, *txt, *value = NULL, c;
 
         if (!txt_)
                 return 0;
 
         t = txt = strdup(txt_);
         if (t == NULL) {
                 printf("Out of memory\n");
                 exit(1);
         }
         while((c=*t) != '\0') {
                 if (c=='=') {
                         *t = '\0';
                         value = t+1;
                 } else if (c=='+') {
                         *t = ' ';
                 } else if (c=='%') {
                         t = convert_query_hexchar(t);
                 } else if (c=='&') {
                         *t = '\0';
                         (*fn)(txt, value);
                         txt = t+1;
                         value = NULL;
                 }
                 t++;
         }
         if (t!=txt)
                 (*fn)(txt, value);
         return 0;
 }