szA = blob_size(pA);
  szB = blob_size(pB);
  sz = szA<szB ? szA : szB;
  rc = memcmp(blob_buffer(pA), blob_buffer(pB), sz);
  if( rc==0 ){
    rc = szA - szB;
  }
  return rc;
}

/*
** Compare two blobs in constant time and return zero if they are equal.
** Constant time comparison only applies for blobs of the same length.
** If lengths are different, immediately returns 1.
*/
int blob_constant_time_cmp(Blob *pA, Blob *pB){
  int szA, szB, i;
  unsigned char *buf1, *buf2;
  unsigned char rc = 0;

  blob_is_init(pA);
  blob_is_init(pB);
  szA = blob_size(pA);
  szB = blob_size(pB);
  if( szA!=szB || szA==0 ) return 1;

  buf1 = blob_buffer(pA);
  buf2 = blob_buffer(pB);

  for( i=0; i<szA; i++ ){
    rc = rc | (buf1[i] ^ buf2[i]);
  }

  return rc;
}

/*
** Compare a blob to a string.  Return TRUE if they are equal.
*/
int blob_eq_str(Blob *pBlob, const char *z, int n){

    cgi_set_cookie(zCookieName, "", login_cookie_path(), -86400);
    redirect_to_g();
  }
  if( g.perm.Password && zPasswd && (zNew1 = P("n1"))!=0 && (zNew2 = P("n2"))!=0 ){
    /* The user requests a password change */
    zSha1Pw = sha1_shared_secret(zPasswd, g.zLogin, 0);
    if( db_int(1, "SELECT 0 FROM user"
                  " WHERE uid=%d"
                  " AND (constant_time_cmp(pw,%Q)=0"
                  "      OR constant_time_cmp(pw,%Q)=0)", 
                  g.userUid, zSha1Pw, zPasswd) ){
      sleep(1);
      zErrMsg = 
         @ <p><span class="loginError">
         @ You entered an incorrect old password while attempting to change
         @ your password.  Your password is unchanged.
         @ </span></p>
      ;

    */
    zSha1Pw = sha1_shared_secret(zPasswd, zUsername, 0);
    uid = db_int(0,
        "SELECT uid FROM user"
        " WHERE login=%Q"
        "   AND length(cap)>0 AND length(pw)>0"
        "   AND login NOT IN ('anonymous','nobody','developer','reader')"
        "   AND (constant_time_cmp(pw,%Q)=0 OR constant_time_cmp(pw,%Q)=0)",
        zUsername, zSha1Pw, zPasswd
    );
    if( uid<=0 ){
      sleep(1);
      zErrMsg = 
         @ <p><span class="loginError">
         @ You entered an unknown user or an incorrect password.
         @ </span></p>

    @ <tr><td></td>
    @ <td><input type="submit" value="Change Password" /></td></tr>
    @ </table>
    @ </form>
  }
  style_footer();
}

/*
** SQL function for constant time comparison of two values.
** Sets result to 0 if two values are equal.
*/
static void constant_time_cmp_function(
 sqlite3_context *context,
 int argc,
 sqlite3_value **argv
){
  const unsigned char *buf1, *buf2;
  int len, i;
  unsigned char rc = 0;

  assert( argc==2 );
  len = sqlite3_value_bytes(argv[0]);
  if( len==0 || len!=sqlite3_value_bytes(argv[1]) ){
    rc = 1;
  }else{
    buf1 = sqlite3_value_text(argv[0]);
    buf2 = sqlite3_value_text(argv[1]);
    for( i=0; i<len; i++ ){
      rc = rc | (buf1[i] ^ buf2[i]);
    }
  }
  sqlite3_result_int(context, rc);
}

/*
** Attempt to find login credentials for user zLogin on a peer repository
** with project code zCode.  Transfer those credentials to the local 
** repository.
**
** Return true if a transfer was made and false if not.

       zCode
  );
  if( zOtherRepo==0 ) return 0;  /* No such peer repository */

  rc = sqlite3_open(zOtherRepo, &pOther);
  if( rc==SQLITE_OK ){
    sqlite3_create_function(pOther,"now",0,SQLITE_ANY,0,db_now_function,0,0);
    sqlite3_create_function(pOther, "constant_time_cmp", 2, SQLITE_UTF8, 0,
		  constant_time_cmp_function, 0, 0);
    sqlite3_busy_timeout(pOther, 5000);
    zSQL = mprintf(
      "SELECT cexpire FROM user"
      " WHERE login=%Q"
      "   AND ipaddr=%Q"

      "   AND length(cap)>0"
      "   AND length(pw)>0"
      "   AND cexpire>julianday('now')"
      "   AND constant_time_cmp(cookie,%Q)=0",
      zLogin, zRemoteAddr, zHash
    );
    pStmt = 0;
    rc = sqlite3_prepare_v2(pOther, zSQL, -1, &pStmt, 0);
    if( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
      db_multi_exec(
        "UPDATE user SET cookie=%Q, ipaddr=%Q, cexpire=%.17g"
        " WHERE login=%Q",

  if( fossil_strcmp(zLogin, "anonymous")==0 ) return 0;
  if( fossil_strcmp(zLogin, "nobody")==0 ) return 0;
  if( fossil_strcmp(zLogin, "developer")==0 ) return 0;
  if( fossil_strcmp(zLogin, "reader")==0 ) return 0;
  uid = db_int(0, 
    "SELECT uid FROM user"
    " WHERE login=%Q"

    "   AND ipaddr=%Q"
    "   AND cexpire>julianday('now')"
    "   AND length(cap)>0"
    "   AND length(pw)>0"
    "   AND constant_time_cmp(cookie,%Q)=0",
    zLogin, zRemoteAddr, zCookie
  );
  return uid;
}

/*
** This routine examines the login cookie to see if it exists and
** and is valid.  If the login cookie checks out, it then sets 

  const char *zCookie;          /* Text of the login cookie */
  const char *zIpAddr;          /* Raw IP address of the requestor */
  char *zRemoteAddr;            /* Abbreviated IP address of the requestor */
  const char *zCap = 0;         /* Capability string */

  /* Only run this check once.  */
  if( g.userUid!=0 ) return;

  sqlite3_create_function(g.db, "constant_time_cmp", 2, SQLITE_UTF8, 0,
		  constant_time_cmp_function, 0, 0);

  /* If the HTTP connection is coming over 127.0.0.1 and if
  ** local login is disabled and if we are using HTTP and not HTTPS, 
  ** then there is no need to check user credentials.
  **
  ** This feature allows the "fossil ui" command to give the user
  ** full access rights without having to log in.

    db_ephemeral_blob(&q, 0, &pw);
    szPw = blob_size(&pw);
    blob_zero(&combined);
    blob_copy(&combined, pNonce);
    blob_append(&combined, blob_buffer(&pw), szPw);
    sha1sum_blob(&combined, &hash);
    assert( blob_size(&hash)==40 );
    rc = blob_constant_time_cmp(&hash, pSig);
    blob_reset(&hash);
    blob_reset(&combined);
    if( rc!=0 && szPw!=40 ){
      /* If this server stores cleartext passwords and the password did not
      ** match, then perhaps the client is sending SHA1 passwords.  Try
      ** again with the SHA1 password.
      */
      const char *zPw = db_column_text(&q, 0);
      char *zSecret = sha1_shared_secret(zPw, blob_str(pLogin), 0);
      blob_zero(&combined);
      blob_copy(&combined, pNonce);
      blob_append(&combined, zSecret, -1);
      free(zSecret);
      sha1sum_blob(&combined, &hash);
      rc = blob_constant_time_cmp(&hash, pSig);
      blob_reset(&hash);
      blob_reset(&combined);
    }
    if( rc==0 ){
      const char *zCap;
      zCap = db_column_text(&q, 1);
      login_set_capabilities(zCap, 0);