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+/*
+** Copyright (c) 2017 D. Richard Hipp
+**
+** This program is free software; you can redistribute it and/or
+** modify it under the terms of the Simplified BSD License (also
+** known as the "2-Clause License" or "FreeBSD License".)
+**
+** This program is distributed in the hope that it will be useful,
+** but without any warranty; without even the implied warranty of
+** merchantability or fitness for a particular purpose.
+**
+** Author contact information:
+**   drh@hwaci.com
+**   http://www.hwaci.com/drh/
+**
+*******************************************************************************
+**
+** This file contains code used to manage a cookie that stores user-specific
+** display preferences for the web interface.
+**
+** cookie_parse(void);
+**
+**    Read and parse the display preferences cookie.
+**
+** cookie_read_parameter(zQP, zPName);
+**
+**    If query parameter zQP does not exist but zPName does exist in
+**    the parsed cookie, then initialize zQP to hold the same value
+**    as the zPName element in the parsed cookie.
+**
+** cookie_write_parameter(zQP, zPName, zDefault);
+**
+**    If query parameter zQP exists and if it has a different value from
+**    the zPName parameter in the parsed cookie, then replace the value of
+**    zPName with the value of zQP.  If zQP exists but zPName does not
+**    exist, then zPName is created.  If zQP does not exist or if it has
+**    the same value as zPName, then this routine is a no-op.
+**
+** cookie_link_parameter(zQP, zPName, zDefault);
+**
+**    This does both cookie_read_parameter() and cookie_write_parameter()
+**    all at once.
+**
+** cookie_render();
+**
+**    If any prior calls to cookie_write_parameter() have changed the
+**    value of the user preferences cookie, this routine will cause the
+**    new cookie value to be included in the HTTP header for the current
+**    web page.  This routine is a destructor for this module and should
+**    be called once.
+**
+** char *cookie_value(zPName, zDefault);
+**
+**    Look up the value of a cookie parameter zPName.  Return zDefault if
+**    there is no display preferences cookie or if zPName does not exist.
+*/
+#include "config.h"
+#include "cookies.h"
+#include <assert.h>
+#include <string.h>
+
+#if INTERFACE
+/* the standard name of the display settings cookie for fossil */
+# define DISPLAY_SETTINGS_COOKIE    "fossil_display_settings"
+#endif
+
+
+/*
+** State information private to this module
+*/
+#define COOKIE_NPARAM  10
+static struct {
+  char *zCookieValue;         /* Value of the user preferences cookie */
+  int bChanged;               /* True if any value has changed */
+  int bIsInit;                /* True after initialization */
+  int nParam;                 /* Number of parameters in the cookie */
+  struct {
+    const char *zPName;         /* Name of a parameter */
+    char *zPValue;              /* Value of that parameter */
+  } aParam[COOKIE_NPARAM];
+} cookies;
+
+/* Initialize this module by parsing the content of the cookie named
+** by DISPLAY_SETTINGS_COOKIE
+*/
+void cookie_parse(void){
+  char *z;
+  if( cookies.bIsInit ) return;
+  z = (char*)P(DISPLAY_SETTINGS_COOKIE);
+  if( z==0 ) z = "";
+  cookies.zCookieValue = z = fossil_strdup(z);
+  cookies.bIsInit = 1;
+  while( cookies.nParam<COOKIE_NPARAM ){
+    while( fossil_isspace(z[0]) ) z++;
+    if( z[0]==0 ) break;
+    cookies.aParam[cookies.nParam].zPName = z;
+    while( *z && *z!='=' && *z!=',' ){ z++; }
+    if( *z=='=' ){
+      *z = 0;
+      z++;
+      cookies.aParam[cookies.nParam].zPValue = z;
+      while( *z && *z!=',' ){ z++; }
+      if( *z ){
+        *z = 0;
+        z++;
+      }
+      dehttpize(cookies.aParam[cookies.nParam].zPValue);
+    }else{
+      if( *z ){ *z++ = 0; }
+      cookies.aParam[cookies.nParam].zPValue = "";
+    }
+    cookies.nParam++;
+  }
+}
+
+#define COOKIE_READ  1
+#define COOKIE_WRITE 2
+static void cookie_readwrite(
+  const char *zQP,        /* Name of the query parameter */
+  const char *zPName,     /* Name of the cooking setting */
+  const char *zDflt,      /* Default value for the query parameter */
+  int flags               /* READ or WRITE or both */
+){
+  const char *zQVal = P(zQP);
+  int i;
+  cookie_parse();
+  for(i=0; i<cookies.nParam && strcmp(zPName,cookies.aParam[i].zPName); i++){}
+  if( zQVal==0 && (flags & COOKIE_READ)!=0 && i<cookies.nParam ){
+    cgi_set_parameter_nocopy(zQP, cookies.aParam[i].zPValue, 1);
+    return;
+  }
+  if( zQVal==0 ){
+    zQVal = zDflt;
+    if( flags & COOKIE_WRITE ) cgi_set_parameter_nocopy(zQP, zQVal, 1);
+  }
+  if( (flags & COOKIE_WRITE)!=0
+   && i<COOKIE_NPARAM
+   && (i==cookies.nParam || strcmp(zQVal, cookies.aParam[i].zPValue))
+  ){
+    if( i==cookies.nParam ){
+      cookies.aParam[i].zPName = zPName;
+      cookies.nParam++;
+    }
+    cookies.aParam[i].zPValue = (char*)zQVal;
+    cookies.bChanged = 1;
+  }
+}
+
+/* If query parameter zQP is missing, initialize it using the zPName
+** value from the user preferences cookie
+*/
+void cookie_read_parameter(const char *zQP, const char *zPName){
+  cookie_readwrite(zQP, zPName, 0, COOKIE_READ);
+}
+
+/* Update the zPName value of the user preference cookie to match
+** the value of query parameter zQP.
+*/
+void cookie_write_parameter(
+  const char *zQP,
+  const char *zPName,
+  const char *zDflt
+){
+  cookie_readwrite(zQP, zPName, zDflt, COOKIE_WRITE);
+}
+
+/* Use the zPName user preference value as a default for zQP and record
+** any changes to the zQP value back into the cookie.
+*/
+void cookie_link_parameter(
+  const char *zQP,       /* The query parameter */
+  const char *zPName,    /* The name of the cookie value */
+  const char *zDflt      /* Default value for the parameter */
+){
+  cookie_readwrite(zQP, zPName, zDflt, COOKIE_READ|COOKIE_WRITE);
+}
+
+/* Update the user preferences cookie, if necessary, and shut down
+** this module. The cookie is only emitted if its value has actually
+** changed since the request started and the "udc" (Update Display
+** Cookie) URL argument was provided.
+**
+** Historical note: from 2021-03-02 [71a2d68a7a113e7c] until
+** 2023-01-16, the udc was not observed (it had been prior to that),
+** and that led to the unfortunate side effect that a timeline link
+** from the /reports page would end up persistently setting a user's
+** timeline length preference to the number of items in that
+** report. In a /chat discussion it was agreed that updating the
+** cookie requires explicit opt-in via the udc argument or ?skin=...,
+** which implies udc.
+*/
+void cookie_render(void){
+  if( cookies.bChanged && P("udc")!=0 ){
+    Blob new;
+    int i;
+    blob_init(&new, 0, 0);
+    for(i=0;i<cookies.nParam;i++){
+      if( i>0 ) blob_append(&new, ",", 1);
+      blob_appendf(&new, "%s=%T",
+          cookies.aParam[i].zPName, cookies.aParam[i].zPValue);
+    }
+    cgi_set_cookie(DISPLAY_SETTINGS_COOKIE, blob_str(&new), 0, 31536000);
+  }
+  cookies.bIsInit = 0;
+}
+
+/* Return the value of a preference cookie.
+*/
+const char *cookie_value(const char *zPName, const char *zDefault){
+  int i;
+  assert( zPName!=0 );
+  cookie_parse();
+  for(i=0; i<cookies.nParam && strcmp(zPName,cookies.aParam[i].zPName); i++){}
+  return i<cookies.nParam ? cookies.aParam[i].zPValue : zDefault;
+}
+
+/* Return the number of characters of hex in the prefix to the
+** given string.
+*/
+static int hex_prefix_length(const char *z){
+  int i;
+  for(i=0; fossil_isXdigit(z[i]); i++){}
+  return i;
+}
+
+/*
+** WEBPAGE: cookies
+**
+** Show all cookies associated with Fossil.  This shows the text of the
+** login cookie and is hence dangerous if an adversary is looking over
+** your shoulder and is able to read and reproduce that cookie.
+**
+** WEBPAGE: fdscookie
+**
+** Show the current display settings contained in the
+** "fossil_display_settings" cookie.
+*/
+void cookie_page(void){
+  int i;
+  int nCookie = 0;
+  const char *zName = 0;
+  const char *zValue = 0;
+  const char *zLoginCookie = login_cookie_name();
+  int isQP = 0;
+  int bFDSonly = strstr(g.zPath, "fdscookie")!=0;
+  cookie_parse();
+  if( bFDSonly ){
+    style_header("Display Preferences Cookie");
+  }else{
+    style_header("All Cookies");
+  }
+  @ <form method="POST">
+  @ <ol>
+  for(i=0; cgi_param_info(i, &zName, &zValue, &isQP); i++){
+    char *zDel;
+    if( isQP ) continue;
+    if( fossil_isupper(zName[0]) ) continue;
+    if( bFDSonly && strcmp(zName, "fossil_display_settings")!=0 ) continue;
+    zDel = mprintf("del%s",zName);
+    if( P(zDel)!=0 ){
+      const char *zPath = fossil_strcmp(ROBOT_COOKIE,zName)==0
+        ? "/" : 0;
+      cgi_set_cookie(zName, "", zPath, -1);
+      cgi_redirect(g.zPath);
+    }
+    nCookie++;
+    @ <li><p><b>%h(zName)</b>: %h(zValue)
+    @ <input type="submit" name="%h(zDel)" value="Delete">
+    if( fossil_strcmp(zName, DISPLAY_SETTINGS_COOKIE)==0  && cookies.nParam>0 ){
+      int j;
+      @ <p>This cookie remembers your Fossil display preferences.
+      @ <ul>
+      for(j=0; j<cookies.nParam; j++){
+        @ <li>%h(cookies.aParam[j].zPName): "%h(cookies.aParam[j].zPValue)"
+      }
+      @ </ul>
+    }else
+    if( fossil_strcmp(zName, zLoginCookie)==0 ){
+      @ <p>This is your login cookie.  If you delete this cookie, you will
+      @ be logged out.
+    }else
+    if( fossil_strncmp(zName, "fossil-", 7)==0
+     && strlen(zName)==23
+     && hex_prefix_length(&zName[7])==16
+     && hex_prefix_length(zValue)>24
+    ){
+      @ <p>This appears to be a login cookie for another Fossil repository
+      @ in the same website.
+    }else
+    if( fossil_strcmp(zName, ROBOT_COOKIE)==0 ){
+      @ <p>This cookie shows that your web-browser has been tested is
+      @ believed to be operated by a human, not a robot.
+    }
+    else {
+      @ <p>This cookie was not generated by Fossil.  It might be something
+      @ from another program on the same website.
+    }
+    fossil_free(zDel);
+  }
+  @ </ol>
+  @ </form>
+  if( nCookie==0 ){
+    if( bFDSonly ){
+      @ <p><i>Your browser is not holding a "fossil_display_setting" cookie
+      @ for this website</i></p>
+    }else{
+      @ <p><i>Your browser is not holding any cookies for this website</i></p>
+    }
+  }
+  style_finish_page();
+}