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+/*
+** Copyright (c) 2009 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 to a simple text-based CAPTCHA.  Though easily
+** defeated by a sophisticated attacker, this CAPTCHA does at least make
+** scripting attacks more difficult.
+*/
+#include "config.h"
+#include <assert.h>
+#include "captcha.h"
+
+#if INTERFACE
+#define CAPTCHA 2  /* Which captcha rendering to use */
+#endif
+
+/*
+** Convert a hex digit into a value between 0 and 15
+*/
+int hex_digit_value(char c){
+  if( c>='0' && c<='9' ){
+    return c - '0';
+  }else if( c>='a' && c<='f' ){
+    return c - 'a' + 10;
+  }else if( c>='A' && c<='F' ){
+    return c - 'A' + 10;
+  }else{
+    return 0;
+  }
+}
+
+#if CAPTCHA==1
+/*
+** A 4x6 pixel bitmap font for hexadecimal digits
+*/
+static const unsigned int aFont1[] = {
+  0x699996,
+  0x262227,
+  0x69124f,
+  0xf16196,
+  0x26af22,
+  0xf8e196,
+  0x68e996,
+  0xf12244,
+  0x696996,
+  0x699716,
+  0x699f99,
+  0xe9e99e,
+  0x698896,
+  0xe9999e,
+  0xf8e88f,
+  0xf8e888,
+};
+
+/*
+** Render an 8-character hexadecimal string as ascii art.
+** Space to hold the result is obtained from malloc() and should be freed
+** by the caller.
+*/
+char *captcha_render(const char *zPw){
+  char *z = fossil_malloc( 9*12*3*strlen(zPw) + 8 );
+  int i, j, k, m;
+
+  k = 0;
+  for(i=0; i<6; i++){
+    for(j=0; zPw[j]; j++){
+      unsigned char v = hex_digit_value(zPw[j]);
+      v = (aFont1[v] >> ((5-i)*4)) & 0xf;
+      for(m=8; m>=1; m = m>>1){
+        if( v & m ){
+          z[k++] = 0xe2;
+          z[k++] = 0x96;
+          z[k++] = 0x88;
+          z[k++] = 0xe2;
+          z[k++] = 0x96;
+          z[k++] = 0x88;
+        }else{
+          z[k++] = ' ';
+          z[k++] = ' ';
+        }
+      }
+      z[k++] = ' ';
+      z[k++] = ' ';
+    }
+    z[k++] = '\n';
+  }
+  z[k] = 0;
+  return z;
+}
+#endif /* CAPTCHA==1 */
+
+#if CAPTCHA==2
+/*
+** A 5x7 pixel bitmap font for hexadecimal digits
+*/
+static const unsigned char aFont2[] = {
+ /* 0 */  0x0e, 0x13, 0x15, 0x19, 0x11, 0x11, 0x0e,
+ /* 1 */  0x02, 0x06, 0x0A, 0x02, 0x02, 0x02, 0x02,
+ /* 2 */  0x0e, 0x11, 0x01, 0x02, 0x04, 0x08, 0x1f,
+ /* 3 */  0x0e, 0x11, 0x01, 0x06, 0x01, 0x11, 0x0e,
+ /* 4 */  0x02, 0x06, 0x0A, 0x12, 0x1f, 0x02, 0x02,
+ /* 5 */  0x1f, 0x10, 0x1e, 0x01, 0x01, 0x11, 0x0e,
+ /* 6 */  0x0e, 0x11, 0x10, 0x1e, 0x11, 0x11, 0x0e,
+ /* 7 */  0x1f, 0x01, 0x02, 0x04, 0x08, 0x08, 0x08,
+ /* 8 */  0x0e, 0x11, 0x11, 0x0e, 0x11, 0x11, 0x0e,
+ /* 9 */  0x0e, 0x11, 0x11, 0x0f, 0x01, 0x11, 0x0e,
+ /* A */  0x0e, 0x11, 0x11, 0x11, 0x1f, 0x11, 0x11,
+ /* B */  0x1e, 0x11, 0x11, 0x1e, 0x11, 0x11, 0x1e,
+ /* C */  0x0e, 0x11, 0x10, 0x10, 0x10, 0x11, 0x0e,
+ /* D */  0x1c, 0x12, 0x11, 0x11, 0x11, 0x12, 0x1c,
+ /* E */  0x1f, 0x10, 0x10, 0x1c, 0x10, 0x10, 0x1f,
+ /* F */  0x1f, 0x10, 0x10, 0x1e, 0x10, 0x10, 0x10,
+};
+
+/*
+** Render an 8-character hexadecimal string as ascii art.
+** Space to hold the result is obtained from malloc() and should be freed
+** by the caller.
+*/
+char *captcha_render(const char *zPw){
+  char *z = fossil_malloc( 224*strlen(zPw) + 9 );
+  int i, j, k, m;
+
+  k = 0;
+  for(i=0; i<7; i++){
+    for(j=0; zPw[j]; j++){
+      unsigned char v = hex_digit_value(zPw[j]);
+      v = aFont2[v*7+i];
+      for(m=16; m>=1; m = m>>1){
+        if( v & m ){
+          z[k++] = 0xe2;
+          z[k++] = 0x96;
+          z[k++] = 0x88;
+          z[k++] = 0xe2;
+          z[k++] = 0x96;
+          z[k++] = 0x88;
+        }else{
+          z[k++] = 0xe2;
+          z[k++] = 0x96;
+          z[k++] = 0x91;
+          z[k++] = 0xe2;
+          z[k++] = 0x96;
+          z[k++] = 0x91;
+        }
+      }
+      z[k++] = ' ';
+      z[k++] = ' ';
+    }
+    z[k++] = '\n';
+  }
+  z[k] = 0;
+  return z;
+}
+#endif /* CAPTCHA==2 */
+
+
+#if CAPTCHA==3
+static const char *const azFont3[] = {
+ /* 0 */
+ "  __  ",
+ " /  \\ ",
+ "| () |",
+ " \\__/ ",
+
+ /* 1 */
+ " _ ",
+ "/ |",
+ "| |",
+ "|_|",
+
+ /* 2 */
+ " ___ ",
+ "|_  )",
+ " / / ",
+ "/___|",
+
+ /* 3 */
+ " ____",
+ "|__ /",
+ " |_ \\",
+ "|___/",
+
+ /* 4 */
+ " _ _  ",
+ "| | | ",
+ "|_  _|",
+ "  |_| ",
+
+ /* 5 */
+ " ___ ",
+ "| __|",
+ "|__ \\",
+ "|___/",
+
+ /* 6 */
+ "  __ ",
+ " / / ",
+ "/ _ \\",
+ "\\___/",
+
+ /* 7 */
+ " ____ ",
+ "|__  |",
+ "  / / ",
+ " /_/  ",
+
+ /* 8 */
+ " ___ ",
+ "( _ )",
+ "/ _ \\",
+ "\\___/",
+
+ /* 9 */
+ " ___ ",
+ "/ _ \\",
+ "\\_, /",
+ " /_/ ",
+
+ /* A */
+ "      ",
+ "  /\\  ",
+ " /  \\ ",
+ "/_/\\_\\",
+
+ /* B */
+ " ___ ",
+ "| _ )",
+ "| _ \\",
+ "|___/",
+
+ /* C */
+ "  ___ ",
+ " / __|",
+ "| (__ ",
+ " \\___|",
+
+ /* D */
+ " ___  ",
+ "|   \\ ",
+ "| |) |",
+ "|___/ ",
+
+ /* E */
+ " ___ ",
+ "| __|",
+ "| _| ",
+ "|___|",
+
+ /* F */
+ " ___ ",
+ "| __|",
+ "| _| ",
+ "|_|  ",
+};
+
+/*
+** Render an 8-digit hexadecimal string as ascii arg.
+** Space to hold the result is obtained from malloc() and should be freed
+** by the caller.
+*/
+char *captcha_render(const char *zPw){
+  char *z = fossil_malloc( 7*4*strlen(zPw) + 5 );
+  int i, j, k, m;
+  const char *zChar;
+
+  k = 0;
+  for(i=0; i<4; i++){
+    for(j=0; zPw[j]; j++){
+      unsigned char v = hex_digit_value(zPw[j]);
+      zChar = azFont3[4*v + i];
+      for(m=0; zChar[m]; m++){
+        z[k++] = zChar[m];
+      }
+    }
+    z[k++] = '\n';
+  }
+  z[k] = 0;
+  return z;
+}
+#endif /* CAPTCHA==3 */
+
+#if CAPTCHA==4
+static const char *const azFont4[] = {
+  /* 0 */
+  "  ___  ",
+  " / _ \\ ",
+  "| | | |",
+  "| | | |",
+  "| |_| |",
+  " \\___/ ",
+
+  /* 1 */
+  " __ ",
+  "/_ |",
+  " | |",
+  " | |",
+  " | |",
+  " |_|",
+
+  /* 2 */
+  " ___  ",
+  "|__ \\ ",
+  "   ) |",
+  "  / / ",
+  " / /_ ",
+  "|____|",
+
+  /* 3 */
+  " ____  ",
+  "|___ \\ ",
+  "  __) |",
+  " |__ < ",
+  " ___) |",
+  "|____/ ",
+
+  /* 4 */
+  " _  _   ",
+  "| || |  ",
+  "| || |_ ",
+  "|__   _|",
+  "   | |  ",
+  "   |_|  ",
+
+  /* 5 */
+  " _____ ",
+  "| ____|",
+  "| |__  ",
+  "|___ \\ ",
+  " ___) |",
+  "|____/ ",
+
+  /* 6 */
+  "   __  ",
+  "  / /  ",
+  " / /_  ",
+  "| '_ \\ ",
+  "| (_) |",
+  " \\___/ ",
+
+  /* 7 */
+  " ______ ",
+  "|____  |",
+  "    / / ",
+  "   / /  ",
+  "  / /   ",
+  " /_/    ",
+
+  /* 8 */
+  "  ___  ",
+  " / _ \\ ",
+  "| (_) |",
+  " > _ < ",
+  "| (_) |",
+  " \\___/ ",
+
+  /* 9 */
+  "  ___  ",
+  " / _ \\ ",
+  "| (_) |",
+  " \\__, |",
+  "   / / ",
+  "  /_/  ",
+
+  /* A */
+  "          ",
+  "    /\\    ",
+  "   /  \\   ",
+  "  / /\\ \\  ",
+  " / ____ \\ ",
+  "/_/    \\_\\",
+
+  /* B */
+  " ____  ",
+  "|  _ \\ ",
+  "| |_) |",
+  "|  _ < ",
+  "| |_) |",
+  "|____/ ",
+
+  /* C */
+  "  _____ ",
+  " / ____|",
+  "| |     ",
+  "| |     ",
+  "| |____ ",
+  " \\_____|",
+
+  /* D */
+  " _____  ",
+  "|  __ \\ ",
+  "| |  | |",
+  "| |  | |",
+  "| |__| |",
+  "|_____/ ",
+
+  /* E */
+  " ______ ",
+  "|  ____|",
+  "| |__   ",
+  "|  __|  ",
+  "| |____ ",
+  "|______|",
+
+  /* F */
+  " ______ ",
+  "|  ____|",
+  "| |__   ",
+  "|  __|  ",
+  "| |     ",
+  "|_|     ",
+};
+
+/*
+** Render an 8-digit hexadecimal string as ascii arg.
+** Space to hold the result is obtained from malloc() and should be freed
+** by the caller.
+*/
+char *captcha_render(const char *zPw){
+  char *z = fossil_malloc( 10*6*strlen(zPw) + 7 );
+  int i, j, k, m;
+  const char *zChar;
+  unsigned char x;
+  int y;
+
+  k = 0;
+  for(i=0; i<6; i++){
+    x = 0;
+    for(j=0; zPw[j]; j++){
+      unsigned char v = hex_digit_value(zPw[j]);
+      x = (x<<4) + v;
+      switch( x ){
+        case 0x7a:
+        case 0xfa:
+          y = 3;
+          break;
+        case 0x47:
+          y = 2;
+          break;
+        case 0xf6:
+        case 0xa9:
+        case 0xa4:
+        case 0xa1:
+        case 0x9a:
+        case 0x76:
+        case 0x61:
+        case 0x67:
+        case 0x69:
+        case 0x41:
+        case 0x42:
+        case 0x43:
+        case 0x4a:
+          y = 1;
+          break;
+        default:
+          y = 0;
+          break;
+      }
+      zChar = azFont4[6*v + i];
+      while( y && zChar[0]==' ' ){ y--; zChar++; }
+      while( y && z[k-1]==' ' ){ y--; k--; }
+      for(m=0; zChar[m]; m++){
+        z[k++] = zChar[m];
+      }
+    }
+    z[k++] = '\n';
+  }
+  z[k] = 0;
+  return z;
+}
+#endif /* CAPTCHA==4 */
+
+/*
+** COMMAND: test-captcha
+**
+** Render an ASCII-art captcha for numbers given on the command line.
+*/
+void test_captcha(void){
+  int i;
+  sqlite3_uint64 v;
+  char *z;
+
+  for(i=2; i<g.argc; i++){
+    char zHex[30];
+    v = (sqlite3_uint64)strtoll(g.argv[i],0,0);
+    sqlite3_snprintf(sizeof(zHex), zHex, "%llx", v);
+    z = captcha_render(zHex);
+    fossil_print("%s:\n%s", zHex, z);
+    free(z);
+  }
+}
+
+/*
+** Compute a seed value for a captcha.  The seed is public and is sent
+** as a hidden parameter with the page that contains the captcha.  Knowledge
+** of the seed is insufficient for determining the captcha without additional
+** information held only on the server and never revealed.
+*/
+unsigned int captcha_seed(void){
+  unsigned int x;
+  sqlite3_randomness(sizeof(x), &x);
+  x &= 0x7fffffff;
+  return x;
+}
+
+/* The SQL that will rotate the captcha-secret. */
+static const char captchaSecretRotationSql[] = 
+@ SAVEPOINT rotate;
+@ DELETE FROM config
+@  WHERE name GLOB 'captcha-secret-*'
+@    AND mtime<unixepoch('now','-6 hours');
+@ UPDATE config
+@    SET name=format('captcha-secret-%%d',substr(name,16)+1)
+@  WHERE name GLOB 'captcha-secret-*';
+@ UPDATE config
+@    SET name='captcha-secret-1', mtime=unixepoch()
+@  WHERE name='captcha-secret';
+@ REPLACE INTO config(name,value,mtime)
+@   VALUES('captcha-secret',%Q,unixepoch());
+@ RELEASE rotate;
+;
+
+
+/*
+** Create a new random captcha-secret.  Rotate the old one into
+** the captcha-secret-N backups.  Purge captcha-secret-N backups
+** older than 6 hours.
+**
+** Do this on the current database and in all other databases of
+** the same login group.
+*/
+void captcha_secret_rotate(void){
+  char *zNew = db_text(0, "SELECT lower(hex(randomblob(20)))");
+  char *zSql = mprintf(captchaSecretRotationSql/*works-like:"%Q"*/, zNew);
+  char *zErrs = 0;
+  fossil_free(zNew);
+  db_unprotect(PROTECT_CONFIG);
+  db_begin_transaction();
+  sqlite3_exec(g.db, zSql, 0, 0, &zErrs);
+  db_protect_pop();
+  if( zErrs && zErrs[0] ){
+    db_rollback_transaction();
+    fossil_fatal("Unable to rotate captcha-secret\n%s\nERROR: %s\n",
+                 zSql, zErrs);
+  }
+  db_end_transaction(0);
+  login_group_sql(zSql, "", "", &zErrs);
+  if( zErrs ){
+    sqlite3_free(zErrs);  /* Silently ignore errors on other repos */
+  }
+  fossil_free(zSql);
+}
+
+/*
+** Return the value of the N-th more recent captcha-secret.  The
+** most recent captcha-secret is 0.  Others are prior captcha-secrets
+** that have expired, but are retained for a limited period of time
+** so that pending anonymous login cookies and/or captcha dialogs
+** don't malfunction when the captcha-secret changes.
+**
+** Clients should start by using the 0-th captcha-secret.  Only if
+** that one does not work should they advance to 1 and 2 and so forth,
+** until this routine returns a NULL pointer.
+**
+** The value returned is a string obtained from fossil_malloc() and
+** should be freed by the caller.
+**
+** The 0-th captcha secret is the value of Config.Name='captcha-secret'.
+** For N>0, the value is in Config.Name='captcha-secret-$N'.
+*/
+char *captcha_secret(int N){
+  if( N==0 ){
+    return db_text(0, "SELECT value FROM config WHERE name='captcha-secret'");
+  }else{
+    return db_text(0, 
+        "SELECT value FROM config"
+        " WHERE name='captcha-secret-%d'"
+        "   AND mtime>unixepoch('now','-6 hours')", N);
+  }
+}
+
+/*
+** Translate a captcha seed value into the captcha password string.
+** The returned string is static and overwritten on each call to
+** this function.
+**
+** Use the N-th captcha secret to compute the password.  When N==0,
+** a valid password is always returned.  A new captcha-secret will
+** be created if necessary.  But for N>0, the return value might
+** be NULL to indicate that there is no N-th captcha-secret.
+*/
+const char *captcha_decode(unsigned int seed, int N){
+  char *zSecret;
+  const char *z;
+  Blob b;
+  static char zRes[20];
+
+  zSecret = captcha_secret(N);
+  if( zSecret==0 ){
+    if( N>0 ) return 0;
+    db_unprotect(PROTECT_CONFIG);
+    db_multi_exec(
+      "REPLACE INTO config(name,value)"
+      " VALUES('captcha-secret', lower(hex(randomblob(20))));"
+    );
+    db_protect_pop();
+    zSecret = captcha_secret(0);
+    assert( zSecret!=0 );
+  }
+  blob_init(&b, 0, 0);
+  blob_appendf(&b, "%s-%x", zSecret, seed);
+  sha1sum_blob(&b, &b);
+  z = blob_buffer(&b);
+  memcpy(zRes, z, 8);
+  zRes[8] = 0;
+  fossil_free(zSecret);
+  return zRes;
+}
+
+/*
+** Return true if a CAPTCHA is required for editing wiki or tickets or for
+** adding attachments.
+**
+** A CAPTCHA is required in those cases if the user is not logged in (if they
+** are user "nobody") and if the "require-captcha" setting is true.  The
+** "require-captcha" setting is controlled on the Admin/Access page.  It
+** defaults to true.
+*/
+int captcha_needed(void){
+  return login_is_nobody() && db_get_boolean("require-captcha", 1);
+}
+
+/*
+** If a captcha is required but the correct captcha code is not supplied
+** in the query parameters, then return false (0).
+**
+** If no captcha is required or if the correct captcha is supplied, return
+** true (non-zero).
+**
+** The query parameters examined are "captchaseed" for the seed value and
+** "captcha" for text that the user types in response to the captcha prompt.
+*/
+int captcha_is_correct(int bAlwaysNeeded){
+  const char *zSeed;
+  const char *zEntered;
+  const char *zDecode;
+  char z[30];
+  int i;
+  int n = 0;
+  if( !bAlwaysNeeded && !captcha_needed() ){
+    return 1;  /* No captcha needed */
+  }
+  zSeed = P("captchaseed");
+  if( zSeed==0 ) return 0;
+  zEntered = P("captcha");
+  if( zEntered==0 || strlen(zEntered)!=8 ) return 0;
+  do{
+    zDecode = captcha_decode((unsigned int)atoi(zSeed), n++);
+    if( zDecode==0 ) return 0;
+    assert( strlen(zDecode)==8 );
+    for(i=0; i<8; i++){
+      char c = zEntered[i];
+      if( c>='A' && c<='F' ) c += 'a' - 'A';
+      if( c=='O' ) c = '0';
+      z[i] = c;
+    }
+  }while( strncmp(zDecode,z,8)!=0 );
+  return 1;
+}
+
+/*
+** Generate a captcha display together with the necessary hidden parameter
+** for the seed and the entry box into which the user will type the text of
+** the captcha.  This is typically done at the very bottom of a form.
+**
+** This routine is a no-op if no captcha is required.
+**
+** Flag values:
+**
+**     0x01     Show the "Submit" button in the form.
+**     0x02     Always generate the captcha, even if not required
+*/
+void captcha_generate(int mFlags){
+  unsigned int uSeed;
+  const char *zDecoded;
+  char *zCaptcha;
+
+  if( !captcha_needed() && (mFlags & 0x02)==0 ) return;
+  uSeed = captcha_seed();
+  zDecoded = captcha_decode(uSeed, 0);
+  zCaptcha = captcha_render(zDecoded);
+  @ <div class="captcha"><table class="captcha"><tr><td><pre class="captcha">
+  @ %h(zCaptcha)
+  @ </pre>
+  @ Enter security code shown above:
+  @ <input type="hidden" name="captchaseed" value="%u(uSeed)">
+  @ <input type="text" name="captcha" size="8" autofocus>
+  if( mFlags & 0x01 ){
+    @ <input type="submit" value="Submit">
+  }
+  @ <br/>\
+  captcha_speakit_button(uSeed, 0);
+  @ </td></tr></table></div>
+}
+
+/*
+** Add a "Speak the captcha" button.
+*/
+void captcha_speakit_button(unsigned int uSeed, const char *zMsg){
+  if( zMsg==0 ) zMsg = "Speak the text";
+  @ <input aria-label="%h(zMsg)" type="button" value="%h(zMsg)" \
+  @ id="speakthetext">
+  @ <script nonce="%h(style_nonce())">/* captcha_speakit_button() */
+  @ document.getElementById("speakthetext").onclick = function(){
+  @   var audio = window.fossilAudioCaptcha \
+  @ || new Audio("%R/captcha-audio/%u(uSeed)");
+  @   window.fossilAudioCaptcha = audio;
+  @   audio.currentTime = 0;
+  @   audio.play();
+  @ }
+  @ </script>
+}
+
+/*
+** WEBPAGE: test-captcha
+**
+** If the name query parameter is provided, then render the hex value of
+** the name using the captcha font.
+**
+** Otherwise render the captcha screen.  The "show-button" parameter causes
+** the submit button to be rendered.
+*/
+void captcha_test(void){
+  const char *zPw = P("name");
+  if( zPw==0 || zPw[0]==0 ){
+    (void)exclude_spiders(1);
+    @ <hr><p>The captcha is shown above.  Add a name=HEX query parameter
+    @ to see how HEX would be rendered in the current captcha font.
+    @ <h2>Debug/Testing Values:</h2>
+    @ <ul>
+    @ <li> g.isRobot = %d(g.isRobot)
+    @ <li> g.zLogin = %h(g.zLogin)
+    @ <li> login_cookie_welformed() = %d(login_cookie_wellformed())
+    @ <li> captcha_is_correct(1) = %d(captcha_is_correct(1)).
+    @ </ul>
+    style_finish_page();
+  }else{
+    style_set_current_feature("test");
+    style_header("Captcha Test");
+    @ <pre class="captcha">
+    @ %s(captcha_render(zPw))
+    @ </pre>
+    style_finish_page();
+  }
+}
+
+/*
+** WEBPAGE: honeypot
+** This page is a honeypot for spiders and bots.
+*/
+void honeypot_page(void){
+  (void)exclude_spiders(0);
+}
+
+/*
+** Check to see if the current request is coming from an agent that 
+** self-identifies as a spider.
+**
+** If the agent does not claim to be a spider or if the user has logged
+** in (even as anonymous), then return 0 without doing anything.
+**
+** But if the user agent does self-identify as a spider and there is
+** no login, offer a captcha challenge to allow the user agent to prove
+** that he is human and return non-zero.
+**
+** If the bTest argument is non-zero, then show the captcha regardless of
+** how the agent identifies.  This is used for testing only.
+*/
+int exclude_spiders(int bTest){
+  if( !bTest ){
+    if( g.zLogin!=0 ) return 0;  /* Logged in.  Consider them human */
+    if( login_cookie_wellformed() ){
+      /* Logged into another member of the login group */
+      return 0;
+    }
+  }
+
+  /* This appears to be a spider.  Offer the captcha */
+  style_set_current_feature("captcha");
+  style_header("Captcha");
+  style_submenu_enable(0);
+  @ <form method='POST' action='%R/ityaar'>
+  @ <h2>Prove that you are human:
+  if( bTest ){
+    @ <input type="hidden" name="istest" value="1">
+  }
+  captcha_generate(3);
+  @ </form>
+  if( !bTest ){
+    if( P("fossil-goto")==0 ){
+      cgi_set_cookie("fossil-goto", cgi_reconstruct_original_url(), 0, 600);
+    }
+    cgi_append_header("X-Robot: 1\r\n");
+    style_finish_page();
+  }
+  return 1;
+}
+
+/*
+** WEBPAGE: ityaar
+**
+** This is the action for the form that is the captcha.  Not intended
+** for external use.  "ityaar" is an acronym "I Think You Are A Robot".
+**
+** If the captcha is correctly solved, then an anonymous login cookie
+** is set.  Regardless of whether or not the captcha was solved, this
+** page always redirects to the fossil-goto cookie.
+*/
+void captcha_callback(void){
+  int bTest = atoi(PD("istest","0"));
+  if( captcha_is_correct(1) ){
+    if( bTest==0 ){
+      if( !login_cookie_wellformed() ){
+        /* ^^^^--- Don't overwrite a valid login on another repo! */
+        login_set_anon_cookie(0, 0);
+      }
+      cgi_append_header("X-Robot: 0\r\n");
+    }
+    login_redirect_to_g();
+  }else{
+    g.isRobot = 1;
+    (void)exclude_spiders(bTest);
+    if( bTest ){
+      @ <hr><p>Wrong code.  Try again
+      style_finish_page();
+    }
+  }
+}
+
+
+/*
+** Generate a WAV file that reads aloud the hex digits given by
+** zHex.
+*/
+static void captcha_wav(const char *zHex, Blob *pOut){
+  int i;
+  const int szWavHdr = 44;
+  blob_init(pOut, 0, 0);
+  blob_resize(pOut, szWavHdr);  /* Space for the WAV header */
+  pOut->nUsed = szWavHdr;
+  memset(pOut->aData, 0, szWavHdr);
+  if( zHex==0 || zHex[0]==0 ) zHex = "0";
+  for(i=0; zHex[i]; i++){
+    int v = hex_digit_value(zHex[i]);
+    int sz;
+    int nData;
+    const unsigned char *pData;
+    char zSoundName[50];
+    sqlite3_snprintf(sizeof(zSoundName),zSoundName,"sounds/%c.wav",
+                     "0123456789abcdef"[v]);
+    /* Extra silence in between letters */
+    if( i>0 ){
+      int nQuiet = 3000;
+      blob_resize(pOut, pOut->nUsed+nQuiet);
+      memset(pOut->aData+pOut->nUsed-nQuiet, 0x80, nQuiet);
+    }
+    pData = builtin_file(zSoundName, &sz);
+    nData = sz - szWavHdr;
+    blob_resize(pOut, pOut->nUsed+nData);
+    memcpy(pOut->aData+pOut->nUsed-nData, pData+szWavHdr, nData);
+    if( zHex[i+1]==0 ){
+      int len = pOut->nUsed + 36;
+      memcpy(pOut->aData, pData, szWavHdr);
+      pOut->aData[4] = (char)(len&0xff);
+      pOut->aData[5] = (char)((len>>8)&0xff);
+      pOut->aData[6] = (char)((len>>16)&0xff);
+      pOut->aData[7] = (char)((len>>24)&0xff);
+      len = pOut->nUsed;
+      pOut->aData[40] = (char)(len&0xff);
+      pOut->aData[41] = (char)((len>>8)&0xff);
+      pOut->aData[42] = (char)((len>>16)&0xff);
+      pOut->aData[43] = (char)((len>>24)&0xff);
+    }
+  }
+}
+
+/*
+** WEBPAGE: /captcha-audio
+**
+** Return a WAV file that pronounces the digits of the captcha that
+** is determined by the seed given in the name= query parameter.
+*/
+void captcha_wav_page(void){
+  const char *zSeed = PD("name","0");
+  const char *zDecode = captcha_decode((unsigned int)atoi(zSeed), 0);
+  Blob audio;
+  captcha_wav(zDecode, &audio);
+  cgi_set_content_type("audio/wav");
+  cgi_set_content(&audio);
+}
+
+/*
+** WEBPAGE: /test-captcha-audio
+**
+** Return a WAV file that pronounces the hex digits of the name=
+** query parameter.
+*/
+void captcha_test_wav_page(void){
+  const char *zSeed = P("name");
+  Blob audio;
+  captcha_wav(zSeed, &audio);
+  cgi_set_content_type("audio/wav");
+  cgi_set_content(&audio);
+}