Atwiejsze toczenie dziki ShopTurn1 wydanie 2001Wszelkie prawa zastrzeone Powielanie lub przenoszenie poszczeglnych fragmentw tekstu, zdj lub rysunkw bez pisemnej zgody wydawcy jest niedozwolone. Dotyczy to zarwno powielania w formie fotokopii lub z uyciem innej metody jak i przenoszenia na filmy, tamy, pyty, transparenty robocze lub inne media.Niniejsza instrukcja dla pocztkujcych powstaa we wsppracy firm SIEMENS AG Automatisierungs- und Antriebstechnik Motion Control Systems Postfach 3180, D-91050 Erlangen oraz R. KELLER GmbH Siegfried Keller, Stefan Nover, Klaus Reckermann, Kai Schmitz Postfach 131663, D-42043 WuppertalNr katalogowy: 6FC5095-0AA80-0NP0Podrcznik treningowy ShopTurnWstpSzybciej od rysunku do obrabianego przedmiotu - ale jak? Dotychczas obrbka sterowana numerycznie wizaa si przewanie ze skomplikowanymi, abstrakcyjnie kodowanymi programami.
Bya to praca, ktr mogli wykonywa jedynie specjalici. W ten sposb jednak, kady fachowiec uczy si swojego rzemiosa, a dziki dowiadczeniu w dziedzinie tradycyjnej obrbki skrawaniem, potrafi w kadej chwili wykona nawet najtrudniejsze zadanie - chocia nie zawsze jest to opacalne. Dla tych wanie fachowcw naleao stworzy moliwo wykorzystywania wiedzy w sposb wydajny, za pomoc obrabiarek sterowanych numerycznie.
Dlatego SIEMENS konstruujc ShopTurn, poszed drog, ktra pozwala fachowcowi omin skomplikowane kodowanie. Takim fachowcom SIEMENS daje do rki SINUMERIK, czyli system sterujcy nowej generacji: Rozwizanie brzmi: zamiast programowa stwrz plan obrbki. Dziki wykonaniu planu obrbki z dokadnym - jak na fachowca przystao - ustaleniem kolejnoci procesw, uytkownik ShopTurn przy skrawaniu moe zaj si wycznie korzystaniem ze swoich waciwych umiejtnoci, ze swojego knowhow. Przy uyciu ShopTurn nawet najbardziej skomplikowane kontury i obrabiane przedmioty daj si z atwoci wykonywa dziki zintegrowanemu i wydajnemu procesowi generowania drogi najazdu i odjazdu.
Dlatego nowa regua brzmi: atwiej i szybciej od rysunku do przedmiotu - dziki ShopTurn! Chocia ShopTurn faktycznie jest atwy do opanowania, dziki temu materiaowi treningowemu moliwe bdzie szybsze wejcie do nowego wiata obrbki. Zanim jednak przejdziemy do waciwego posugiwania si ShopTurn, w pierwszych trzech rozdziaach zajmiemy si najwaniejszymi tematami: Wymienimy zalety pracy z ShopTurn. Zaprezentujemy podstawy obsugi. Objanimy pocztkujcym geometryczne i technologiczne podstawy obrbki. Po tej czci teoretycznej, zajmiemy si praktycznym wykorzystaniem ShopTurn: Na czterech przykadach przedstawimy moliwoci obrbki przy uyciu ShopTurn, przy czym stopie trudnoci w tych przykadach bdzie sukcesywnie podwyszany.
Na pocztku objanimy dziaanie wszystkich przyciskw, potem bdziemy zachca do samodzielnej pracy. Opowiemy, jak przy uyciu ShopTurn wykonuje si automatyczn obrbk skrawaniem. Jeli Pastwo zechc, na zakoczenie mona przeprowadzi test, na ile opanowalicie prac z ShopTurn. Prosimy pamita o tym, e stosowane tu dane technologiczne ze wzgldu na zrnicowanie warunkw w warsztatach maj tylko charakter przykadowy.Tak jak ShopTurn powsta przy pomocy fachowcw, tak samo niniejszy podrcznik treningowy rwnie zosta opracowany przez praktykw. Yczymy Pastwu wiele przyjemnoci i sukcesw przy pracy z ShopTurn.AutorzyErlangen/Wuppertal, sierpie 2001 1Podrcznik treningowy ShopTurnSpis treci1 Korzyci z pracy przy uyciu ShopTurn. 51.1 1.2 1.3 Oszczdzasz czas potrzebny na opanowanie. 5 Oszczdzasz czas potrzebny na programowanie.
6 Oszczdzasz czas potrzebny na produkcj. 82eby wszystko dziaao sprawnie. 102.1 2.2 2.3 Sprawdzona technika. 10 Panel obsugowy maszyny.
11 Zawarto gwnego menu. 133Podstawy dla pocztkujcych. 183.1 Podstawy geometryczne. 18 3.1.1 Osie i paszczyzny. 18 3.1.2 Punkty w obszarze roboczym. 18 3.1.3 Wsprzdne bezwzgldne i przyrostowe. 19 3.1.4 Wsprzdne kartezjaskie i biegunowe.
20 3.1.5 Ruchy konturowe. 21 3.2 Podstawy technologiczne. 22 3.2.1 Prdko skrawania i obroty. 22 3.2.2 Posuw.
234Dobry osprzt. 244.1 Zarzdzanie narzdziami. 24 4.1.1 Wykaz narzdzi. 4.1.2 Wykaz zuycia narzdzi. 4.1.3 Wykaz magazynowy. Stosowane narzdzia. 24 25 25 264.2 4.3 4.4 4.5Narzdzia w magazynku.
27 Przeliczanie dugoci narzdzi. 28 Ustalanie punktu zerowego przedmiotu. 295Przykad 1: Waek stopniowany.
305.1 5.2 5.3 5.4 5.5 5.6 5.7 Zarzdzanie programami i tworzenie programu. 31 Wybieranie narzdzi i wprowadzanie drogi najazdu i odjazdu.
33Projektowanie dowolnych konturw za pomoc kalkulatora konturw i obrbki zgrubnej 35Wykaczanie. 39 Nacinanie gwintu. 40 Gwint. 41 Toczenie rowkw. 422Podrcznik treningowy ShopTurn6Przykad 2: Waek napdowy. 446.1 6.2 6.3 Toczenie poprzeczne.
45 Projektowanie konturu, skrawanie i skrawanie kocowe. 46 Gwint. 527Przykad 3: Waek ksztatowy. 547.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 Toczenie poprzeczne. 55 Projektowanie dowolnego konturu pwyrobu. 56 Projektowanie konturu wyrobu i skrawanie.
57 Skrawanie kocowe. 62 Rowek. 64 Gwint. 67 Wiercenie. 69 Frezowanie kieszeni prostoktnej. 728Przykad 4: Waek drony. 748.1 Wykonanie pierwszej strony przedmiotu.
75 8.1.1 8.1.2 8.1.3 8.1.4 8.1.5 8.1.6 8.1.7 8.1.8 8.2 8.2.1 8.2.2 8.2.3 8.2.4 8.2.5 8.2.6 Toczenie poprzeczne. 75 Wiercenie. 76 Kontur pwyrobu.
77 Kontur wyrobu z pierwszej strony od zewntrz. 77 Podtoczenie.
81 Kontur wyrobu z pierwszej strony od wewntrz. 83 Rozszerzony edytor. 86 Kopiowanie konturu.
87 Toczenie poprzeczne. 88 Wiercenie. 89 Wstawianie konturu pwyrobu. 90 Kontur wyrobu z drugiej strony od zewntrz. 90 Wykonanie asymetrycznego rowka. 93 Kontur wyrobu z drugiej strony od wewntrz.
94Wykonanie drugiej strony przedmiotu. 889Czas na produkcj. 989.1 9.2 9.3 9.4 Najazd na punkt referencyjny. 98 Zamocowanie przedmiotu do obrbki. 99 Ustawianie punktu zerowego przedmiotu.
99 Realizacja planu obrbki. 10010Jak dobrze sobie radzisz z ShopTurn?. 102Wykaz terminw. 1063Podrcznik treningowy ShopTurn04Podrcznik treningowy ShopTurn1 Korzyci z pracy przy uyciu ShopTurnW niniejszym rozdziale przedstawiamy szczeglne zalety pracy z ShopTurn.1.1 Oszczdzasz czas potrzebny na opanowanie poniewa w ShopTurn nie ma adnego kodowania ani obcojzycznych poj, ktrych trzeba si nauczy: Wszystkie wprowadzane dane wyszukuje si w postaci tekstowej.
Poniewa w ShopTurn masz optymalne wsparcie dziki kolorowym grafikom pomocniczym.1poniewa do Graficznego planu obrbki w ShopTurn moesz wprowadzi rwnie polecenia zgodne z DIN/ ISO.N100 G96 S320 LIMS=3000 M4 M8 N105 G18 G54 G90 N110 G0 X32 Z0 N120 G1 X-0.8 F0.1 N130 G0 Z2 N140 G0 G42 X22 Z2 N150 X30 Z-21 1 1 1 1 1 1 poniewa przy tworzeniu planu obrbki w kadej chwili moesz si przecza midzy poszczeglnymi czynnociami a obrazem graficznym obrabianego przedmiotu. 51 Korzyci z pracy przy uyciu ShopTurn1.2 Oszczdzasz czas potrzebny na programowanie. Poniewa ShopTurn zapewnia optymalne wsparcie ju przy wprowadzaniu parametrw technologicznych: Wystarczy tylko wprowadzi parametry Prdko posuwu (lub Posuw ) oraz Prdko skrawania - liczb obrotw ShopTurn ustawi automatycznie po naciniciu przycisku. Poniewa w ShopTurn w ramach jednej fazy prac mona opisa kompletn obrbk a wymagane ruchy pozycjonowania (tu od punktu wymiany narzdzi do obrabianego przedmiotu i z powrotem) s wywoywane automatycznie. Poniewa w Graficznym planie obrbki w ShopTurn wszystkie etapy obrbki s prezentowane w zwizy i przejrzysty sposb. Dziki temu przegld sytuacji jest peny, a tym samym lepsze s moliwoci edycji, nawet przy skomplikowanych cyklach produkcyjnych. Poniewa przy skrawaniu mona czy kilka operacji obrbkowych i konturw.6Podrcznik treningowy ShopTurn poniewa zintegrowany kalkulator konturw moe przetwarza wszelkie dajce si wymyli wymiarowania a mimo to jest atwy i przejrzysty w obsudze - dziki piktogramom i grafice on-line.
Poniewa w kadej chwili uywajc jednego klawisza, mona przechodzi midzy statycznymi obrazami pomocniczymi a dynamiczn grafik on-line. Grafika on-line zapewnia bezporedni kontrol wzrokow wprowadzanych parametrw. Poniewa tworzenie planu obrbki i produkcja nie wykluczaj si: rwnoczenie z produkcj mona opracowywa nowy plan. 71 Korzyci z pracy przy uyciu ShopTurn1.3 Oszczdzasz czas potrzebny na produkcj poniewa mona optymalizowa dobr narzdzi przy skrawaniu konturw pod wzgldem czasowym i technologicznym: due objtoci zbierane s noami zdzierakami, pozostay materia jest wykrywany automatycznie i skrawany ostrzejszymi narzdziami.Pozostay materia poniewa dziki dokadnemu ustalaniu paszczyzny ruchu powrotnego moliwe jest unikanie zbdnych drg najazdu i odjazdu, tym samym mona oszczdza kosztowny czas produkcji. Jest to moliwe dziki nastawom normalna, rozszerzona lub wszystko.
Obrazy pomocnicze w ShopTurnrn 1 Paszczyzna ruchu powrotnego normalna Paszczyzna ruchu powrotnego rozszerzona Paszczyzna ruchu powrotnego wszystko8Podrcznik treningowy ShopTurn poniewa minimalnym nakadem pracy mona zoptymalizowa kolejno obrbki dziki zwartej strukturze planu obrbki (tu np.
Spis tre¶ci I. PHP is a powerful language and the interpreter, whether included in a web server as a module or executed as a separate CGI binary, is able to access files, execute commands and open network connections on the server.
These properties make anything run on a web server insecure by default. PHP is designed specifically to be a more secure language for writing CGI programs than Perl or C, and with correct selection of compile-time and runtime configuration options, and proper coding practices, it can give you exactly the combination of freedom and security you need. As there are many different ways of utilizing PHP, there are many configuration options controlling its behaviour. A large selection of options guarantees you can use PHP for a lot of purposes, but it also means there are combinations of these options and server configurations that result in an insecure setup.
The configuration flexibility of PHP is equally rivalled by the code flexibility. PHP can be used to build complete server applications, with all the power of a shell user, or it can be used for simple server-side includes with little risk in a tightly controlled environment. How you build that environment, and how secure it is, is largely up to the PHP developer. This chapter starts with some general security advice, explains the different configuration option combinations and the situations they can be safely used, and describes different considerations in coding for different levels of security. A completely secure system is a virtual impossibility, so an approach often used in the security profession is one of balancing risk and usability.
If every variable submitted by a user required two forms of biometric validation (such as a retinal scan and a fingerprint), you would have an extremely high level of accountability. It would also take half an hour to fill out a fairly complex form, which would tend to encourage users to find ways of bypassing the security. The best security is often inobtrusive enough to suit the requirements without the user being prevented from accomplishing their work, or over-burdening the code author with excessive complexity.
Indeed, some security attacks are merely exploits of this kind of overly built security, which tends to erode over time. A phrase worth remembering: A system is only as good as the weakest link in a chain. If all transactions are heavily logged based on time, location, transaction type, etc. But the user is only verified based on a single cookie, the validity of tying the users to the transaction log is severely weakened. When testing, keep in mind that you will not be able to test all possibilities for even the simplest of pages. The input you may expect will be completely unrelated to the input given by a disgruntled employee, a cracker with months of time on their hands, or a housecat walking across the keyboard.
This is why it's best to look at the code from a logical perspective, to discern where unexpected data can be introduced, and then follow how it is modified, reduced, or amplified. The Internet is filled with people trying to make a name for themselves by breaking your code, crashing your site, posting inappropriate content, and otherwise making your day interesting. It doesn't matter if you have a small or large site, you are a target by simply being online, by having a server that can be connected to. Many cracking programs do not discern by size, they simply trawl massive IP blocks looking for victims. Try not to become one. Using PHP as a CGI binary is an option for setups that for some reason do not wish to integrate PHP as a module into server software (like Apache), or will use PHP with different kinds of CGI wrappers to create safe chroot and setuid environments for scripts. This setup usually involves installing executable PHP binary to the web server cgi-bin directory.
CERT advisory recommends against placing any interpreters into cgi-bin. Even if the PHP binary can be used as a standalone interpreter, PHP is designed to prevent the attacks this setup makes possible:. Accessing system files: The query information in a url after the question mark (?) is passed as command line arguments to the interpreter by the CGI interface. Usually interpreters open and execute the file specified as the first argument on the command line. When invoked as a CGI binary, PHP refuses to interpret the command line arguments. Accessing any web document on server: The path information part of the url after the PHP binary name, /secret/doc.html is conventionally used to specify the name of the file to be opened and interpreted by the CGI program.
Usually some web server configuration directives (Apache: Action) are used to redirect requests to documents like to the PHP interpreter. With this setup, the web server first checks the access permissions to the directory /secret, and after that creates the redirected request Unfortunately, if the request is originally given in this form, no access checks are made by web server for file /secret/script.php, but only for the /cgi-bin/php file. This way any user able to access /cgi-bin/php is able to access any protected document on the web server. In PHP, compile-time configuration option and runtime configuration directives and can be used to prevent this attack, if the server document tree has any directories with access restrictions. See below for full the explanation of the different combinations.
If your server does not have any content that is not restricted by password or ip based access control, there is no need for these configuration options. If your web server does not allow you to do redirects, or the server does not have a way to communicate to the PHP binary that the request is a safely redirected request, you can specify the option to the configure script. You still have to make sure your PHP scripts do not rely on one or another way of calling the script, neither by directly nor by redirection Redirection can be configured in Apache by using AddHandler and Action directives (see below). This compile-time option prevents anyone from calling PHP directly with a url like Instead, PHP will only parse in this mode if it has gone through a web server redirect rule. Usually the redirection in the Apache configuration is done with the following directives: Action php-script /cgi-bin/php AddHandler php-script.php This option has only been tested with the Apache web server, and relies on Apache to set the non-standard CGI environment variable REDIRECTSTATUS on redirected requests. If your web server does not support any way of telling if the request is direct or redirected, you cannot use this option and you must use one of the other ways of running the CGI version documented here.
To include active content, like scripts and executables, in the web server document directories is sometimes consider an insecure practice. If, because of some configuration mistake, the scripts are not executed but displayed as regular HTML documents, this may result in leakage of intellectual property or security information like passwords. Therefore many sysadmins will prefer setting up another directory structure for scripts that are accessible only through the PHP CGI, and therefore always interpreted and not displayed as such. Also if the method for making sure the requests are not redirected, as described in the previous section, is not available, it is necessary to set up a script docroot that is different from web document root. You can set the PHP script document root by the configuration directive in the, or you can set the environment variable PHPDOCUMENTROOT. If it is set, the CGI version of PHP will always construct the file name to open with this docroot and the path information in the request, so you can be sure no script is executed outside this directory (except for userdir below). Another option usable here is.
When userdir is unset, only thing controlling the opened file name is docroot. Opening an url like does not result in opening a file under users home directory, but a file called user/doc.php under docroot (yes, a directory name starting with a tilde ). If userdir is set to for example publicphp, a request like will open a file called doc.php under the directory named publicphp under the home directory of the user. If the home of the user is /home/user, the file executed is /home/user/publicphp/doc.php. Userdir expansion happens regardless of the docroot setting, so you can control the document root and user directory access separately. When PHP is used as an Apache module it inherits Apache's user permissions (typically those of the 'nobody' user). This has several impacts on security and authorization.
For example, if you are using PHP to access a database, unless that database has built-in access control, you will have to make the database accessable to the 'nobody' user. This means a malicious script could access and modify the database, even without a username and password. It's entirely possible that a web spider could stumble across a database administrator's web page, and drop all of your databases. You can protect against this with Apache authorization, or you can design your own access model using LDAP,.htaccess files, etc.
And include that code as part of your PHP scripts. Often, once security is established to the point where the PHP user (in this case, the apache user) has very little risk attached to it, it is discovered that PHP is now prevented from writing any files to user directories. Or perhaps it has been prevented from accessing or changing databases. It has equally been secured from writing good and bad files, or entering good and bad database transactions. A frequent security mistake made at this point is to allow apache root permissions, or to escalate apache's abilitites in some other way.
Escalating the Apache user's permissions to root is extremely dangerous and may compromise the entire system, so sudo'ing, chroot'ing, or otherwise running as root should not be considered by those who are not security professionals. There are some simpler solutions. By using you can control and restrict what directories are allowed to be used for PHP. You can also set up apache-only areas, to restrict all web based activity to non-user, or non-system, files. PHP is subject to the security built into most server systems with respect to permissions on a file and directory basis.
This allows you to control which files in the filesystem may be read. Care should be taken with any files which are world readable to ensure that they are safe for reading by all users who have access to that filesystem. Since PHP was designed to allow user level access to the filesystem, it's entirely possible to write a PHP script that will allow you to read system files such as /etc/password, modify your ethernet connections, send massive printer jobs out, etc.
This has some obvious implications, in that you need to ensure that the files that you read from and write to are the appropriate ones. Consider the following script, where a user indicates that they'd like to delete a file in their home directory. This assumes a situation where a PHP web interface is regularly used for file management, so the Apache user is allowed to delete files in the user home directories. Przyk³ad 4-1. Poor variable checking leads to. Since the username is postable from a user form, they can submit a username and file belonging to someone else, and delete files.
In this case, you'd want to use some other form of authentication. Consider what could happen if the variables submitted were './etc/' and 'passwd'.
The code would then effectively read. Przyk³ad 4-2. A filesystem attack There are two important measures you should take to prevent these issues. Only allow limited permissions to the PHP web user binary. Check all variables which are submitted.
Here is an improved script. Przyk³ad 4-3. More secure file name checking However, even this is not without it's flaws.
If your authentication system allowed users to create their own user logins, and a user chose the login './etc/', the system is once again exposed. For this reason, you may prefer to write a more customized check. Przyk³ad 4-4. More secure file name checking Depending on your operating system, there are a wide variety of files which you should be concerned about, including device entries (/dev/ or COM1), configuration files (/etc/ files and the.ini files), well known file storage areas (/home/, My Documents), etc. For this reason, it's usually easier to create a policy where you forbid everything except for what you explicitly allow. Nowadays, databases are cardinal components of any web based application by enabling websites to provide varying dynamic content. Since very sensitive or secret informations can be stored in such database, you should strongly consider to protect them somehow.
To retrieve or to store any information you need to connect to the database, send a legitimate query, fetch the result, and close the connecion. Nowadays, the commonly used query language in this interaction is the Structured Query Language (SQL). See how an attacker can. As you can realize, PHP cannot protect your database by itself. The following sections aim to be an introduction into the very basics of how to access and manipulate databases within PHP scripts.
Keep in my mind this simple rule: defence in depth. In the more place you take the more action to increase the protection of your database, the less probability of that an attacker succeeds, and exposes or abuse any stored secret information. Good design of the database schema and the application deals with your greatest fears. The first step is always to create the database, unless you want to use an existing third party's one. When a database is created, it is assigned to an owner, who executed the creation statement.
Usually, only the owner (or a superuser) can do anything with the objects in that database, and in order to allow other users to use it, privileges must be granted. Applications should never connect to the database as its owner or a superuser, because these users can execute any query at will, for example, modifying the schema (e.g. Dropping tables) or deleting its entire content. You may create different database users for every aspect of your application with very limited rights to database objects.
The most required privileges should be granted only, and avoid that the same user can interact with the database in different use cases. This means that if intruders gain access to your database using one of these credentials, they can only effect as many changes as your application can. You are encouraged not to implement all the business logic in the web application (i.e. Your script), instead to do it in the database schema using views, triggers or rules. If the system evolves, new ports will be intended to open to the database, and you have to reimplement the logic in each separate database client. Over and above, triggers can be used to transparently and automatically handle fields, which often provides insight when debugging problems with your application or tracing back transactions.
SSL/SSH protects data travelling from the client to the server, SSL/SSH does not protect the persistent data stored in a database. SSL is an on-the-wire protocol. Once an attacker gains access to your database directly (bypassing the webserver), the stored sensitive data may be exposed or misused, unless the information is protected by the database itself.
Encrypting the data is a good way to mitigate this threat, but very few databases offer this type of data encryption. The easiest way to work around this problem is to first create your own encryption package, and then use it from within your PHP scripts. PHP can assist you in this case with its several extensions, such as and, covering a wide variety of encryption algorithms. The script encrypts the data be stored first, and decrypts it when retrieving. See the references for further examples how encryption works.
In case of truly hidden data, if its raw representation is not needed (i.e. Not be displayed), hashing may be also taken into consideration. The well-known example for the hashing is storing the MD5 hash of a password in a database, instead of the password itself. Many web developers are unaware of how SQL queries can be tampered with, and assume that an SQL query is a trusted command. It means that SQL queries are able to circumvent access controls, thereby bypassing standard authentication and authorization checks, and sometimes SQL queries even may allow access to host operating system level commands. Direct SQL Command Injection is a technique where an attacker creates or alters existing SQL commands to expose hidden data, or to override valuable ones, or even to execute dangerous system level commands on the database host.
This is accomplished by the application taking user input and combining it with static parameters to build a SQL query. The following examples are based on true stories, unfortunately. Owing to the lack of input validation and connecting to the database on behalf of a superuser or the one who can create users, the attacker may create a superuser in your database. Przyk³ad 4-6. Splitting the result set into pages. And making superusers (PostgreSQL and MySQL) $offset = argv0; // beware, no input validation!
$query = 'SELECT id, name FROM products ORDER BY name LIMIT 20 OFFSET $offset;'; // with PostgreSQL $result = pgexec($conn, $query); // with MySQL $result = mysqlquery($query); Normal users click on the 'next', 'prev' links where the $offset is encoded into the URL. The script expects that the incoming $offset is decimal number. However, someone tries to break in with appending 'd form of the following to the URL. Notatka: It is common technique to force the SQL parser to ignore the rest of the query written by the developer with - which is the comment sign in SQL.
A feasible way to gain passwords is to circumvent your search result pages. What the attacker needs only is to try if there is any submitted variable used in SQL statement which is not handled properly. These filters can be set commonly in a preceding form to customize WHERE, ORDER BY, LIMIT and OFFSET clauses in SELECT statements. If your database supports the UNION construct, the attacker may try to append an entire query to the original one to list passwords from an arbitrary table. Using encrypted password fields is strongly encouraged. ' union select '1', concat(uname '-' passwd) as name, '1971-01-01', '0' from usertable; - If this query (playing with the ' and -) were assigned to one of the variables used in $query, the query beast awakened. SQL UPDATEs are also subject to attacking your database.
These queries are also threatened by chopping and appending an entirely new query to it. But the attacker might fiddle with the SET clause. In this case some schema information must be possessed to manipulate the query successfully. This can be acquired by examing the form variable names, or just simply brute forcing. There are not so many naming convention for fields storing passwords or usernames. You may plead that the attacker must possess a piece of information about the database schema in most examples.
You are right, but you never know when and how it can be taken out, and if it happens, your database may be exposed. If you are using an open source, or publicly available database handling package, which may belong to a content management system or forum, the intruders easily produce a copy of a piece of your code. It may be also a security risk if it is a poorly designed one. These attacks are mainly based on exploiting the code not being written with security in mind. Never trust on any kind of input, especially which comes from the client side, even though it comes from a select box, a hidden input field or a cookie. The first example shows that such a blameless query can cause disasters. Never connect to the database as a superuser or as the database owner.
Use always customized users with very limited privileges. Check if the given input has the expected data type. PHP has a wide range of input validating functions, from the simplest ones found in and in (e.g., respectively) onwards the support. If the application waits for numerical input, consider to verify data with, or silently change its type using, or use its numeric representation. Przyk³ad 4-10.
A more secure way to compose a query for paging settype($order, 'integer'); $query = 'SELECT id, name FROM products ORDER BY name LIMIT 20 OFFSET $offset;'; // please note%d in the format string, using%s would be meaningless $query = sprintf('SELECT id, name FROM products ORDER BY name LIMIT 20 OFFSET%d;', $offset);. Quote each non numeric user input which is passed to the database with. As the examples shows, quotes burnt into the static part of the query is not enough, and can be easily hacked. Do not print out any database specific information, especially about the schema, by fair means or foul. You may use stored procedures and previously defined cursors to abstract data access so that users do not directly access tables or views, but this solution has another impacts.
Besides these, you benefit from logging queries either within your script or by the database itself, if it supports. Obviously, the logging is unable to prevent any harmful attempt, but it can be helpful to trace back which application has been circumvented. The log is not useful by itself, but through the information it contains. The more detail is generally better. With PHP security, there are two sides to error reporting. One is beneficial to increasing security, the other is detrimental.
A standard attack tactic involves profiling a system by feeding it improper data, and checking for the kinds, and contexts, of the errors which are returned. This allows the system cracker to probe for information about the server, to determine possible weaknesses. For example, if an attacker had gleaned information about a page based on a prior form submission, they may attempt to override variables, or modify them. Przyk³ad 4-11.
Attacking Variables with a custom HTML page
For example, the very style of a generic PHP error indicates a system is running PHP. If the attacker was looking at an.html page, and wanted to probe for the back-end (to look for known weaknesses in the system), by feeding it the wrong data they may be able to determine that a system was built with PHP. A function error can indicate whether a system may be running a specific database engine, or give clues as to how a web page or programmed or designed. This allows for deeper investigation into open database ports, or to look for specific bugs or weaknesses in a web page. By feeding different pieces of bad data, for example, an attacker can determine the order of authentication in a script, (from the line number errors) as well as probe for exploits that may be exploited in different locations in the script.
A filesystem or general PHP error can indicate what permissions the webserver has, as well as the structure and organization of files on the web server. Developer written error code can aggravate this problem, leading to easy exploitation of formerly 'hidden' information. There are three major solutions to this issue. The first is to scrutinize all functions, and attempt to compensate for the bulk of the errors. The second is to disable error reporting entirely on the running code.
The third is to use PHP's custom error handling functions to create your own error handler. Depending on your security policy, you may find all three to be applicable to your situation. One way of catching this issue ahead of time is to make use of PHP's own, to help you secure your code and find variable usage that may be dangerous. By testing your code, prior to deployment, with EALL, you can quickly find areas where your variables may be open to poisoning or modification in other ways. Once you are ready for deployment, by using ENONE, you insulate your code from probing. One feature of PHP that can be used to enhance security is configuring PHP with = off. By turning off the ability for any user-submitted variable to be injected into PHP code, you can reduce the amount of variable poisoning a potential attacker may inflict.
They will have to take the additional time to forge submissions, and your internal variables are effectively isolated from user submitted data. While it does slightly increase the amount of effort required to work with PHP, it has been argued that the benefits far outweigh the effort. Przyk³ad 4-17. Dangerous Variable Usage You should always carefully examine your code to make sure that any variables being submitted from a web browser are being properly checked, and ask yourself the following questions:.
Will this script only affect the intended files?. Can unusual or undesirable data be acted upon?. Can this script be used in unintended ways?. Can this be used in conjunction with other scripts in a negative manner?. Will any transactions be adequately logged?
By adequately asking these questions while writing the script, rather than later, you prevent an unfortunate re-write when you need to increase your security. By starting out with this mindset, you won't guarantee the security of your system, but you can help improve it. You may also want to consider turning off registerglobals, magicquotes, or other convenience settings which may confuse you as to the validity, source, or value of a given variable. Working with PHP in errorreporting(EALL) mode can also help warn you about variables being used before they are checked or initialized (so you can prevent unusual data from being operated upon). In general, security by obscurity is one of the weakest forms of security. But in some cases, every little bit of extra security is desirable. A few simple techniques can help to hide PHP, possibly slowing down an attacker who is attempting to discover weaknesses in your system.
By setting exposephp = off in your php.ini file, you reduce the amount of information available to them. Another tactic is to configure web servers such as apache to parse different filetypes through PHP, either with an.htaccess directive, or in the apache configuration file itself. You can then use misleading file extensions. Notatka: If you want to check out the type and value of a certain, use. If you simply want a human-readable representation of the type for debugging, use. To check for a certain type, do not use, but use the is type functions. If you would like to force a variable to be converted to a certain type, you may either the variable or use the function on it.
Note that a variable may behave in different manners in certain situations, depending on what type it is at the time. For more information, see the section on.
To explicitly convert a value to, use either the (bool) or the (boolean) cast. However, in most cases you do not need to use the cast, since a value will be automatically converted if an operator, function or control structure requires a argument. When converting to, the following values are considered FALSE:. the FALSE. the 0 (zero). the 0.0 (zero).
the empty, and the '0'. an with zero elements. an with zero elements. the special type (including unset variables) Every other value is considered TRUE (including any ).
Floating point precision It is quite usual that simple decimal fractions like 0.1 or 0.7 cannot be converted into their internal binary counterparts without a little loss of precision. This can lead to confusing results: for example, floor((0.1+0.7).10) will usually return 7 instead of the expected 8 as the result of the internal representation really being something like 7. This is related to the fact that it is impossible to exactly express some fractions in decimal notation with a finite number of digits. For instance, 1/3 in decimal form becomes 0.3333333. So never trust floating number results to the last digit and never compare floating point numbers for equality.
If you really need higher precision, you should use the or functions instead. When a string is evaluated as a numeric value, the resulting value and type are determined as follows. The string will evaluate as a if it contains any of the characters '.' , 'e', or 'E'.
Otherwise, it will evaluate as an integer. The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero). Valid numeric data is an optional sign, followed by one or more digits (optionally containing a decimal point), followed by an optional exponent. The exponent is an 'e' or 'E' followed by one or more digits. When the first expression is a string, the type of the variable will depend on the second expression.
$foo = 1 + '10.5'; // $foo is float (11.5) $foo = 1 + '-1.3e3'; // $foo is float (-1299) $foo = 1 + 'bob-1.3e3'; // $foo is integer (1) $foo = 1 + 'bob3'; // $foo is integer (1) $foo = 1 + '10 Small Pigs'; // $foo is integer (11) $foo = 1 + '10 Little Piggies'; // $foo is integer (11) $foo = '10.0 pigs ' + 1; // $foo is integer (11) $foo = '10.0 pigs ' + 1.0; // $foo is float (11) For more information on this conversion, see the Unix manual page for strtod(3). If you would like to test any of the examples in this section, you can cut and paste the examples and insert the following line to see for yourself what's going on. An array in PHP is actually an ordered map.
A map is a type that maps values to keys. This type is optimized in several ways, so you can use it as a real array, or a list (vector), hashtable (which is an implementation of a map), dictionary, collection, stack, queue and probably more. Because you can have another PHP-array as a value, you can also quite easily simulate trees.
Explanation of those structures is beyond the scope of this manual, but you'll find at least one example for each of those structures. For more information about those structures, we refer you to external literature about this broad topic. An can be created by the language-construct.
It takes a certain number of comma-separated key = value pairs. A key is either a nonnegative or a. If a key is the standard representation of a non-negative, it will be interpreted as such (i.e. '8' will be interpreted as 8, while '08' will be interpreted as '08'). A value can be anything. If you omit a key, the maximum of the integer-indices is taken, and the new key will be that maximum + 1.
If no integer-indices exist yet, the key will be 0 (zero). If you specify a key that already has a value assigned to it, that value will be overwritten. Array( key = value.
) // key is either or nonnegative // value can be anything. You can also modify an existing array, by explicitly setting values. This is done by assigning values to the array while specifying the key in brackets. You can also omit the key, add an empty pair of brackets (' ') to the variable-name in that case. $arr key = value; $arr = value; // key is either or nonnegative // value can be anything If $arr doesn't exist yet, it will be created.
So this is also an alternative way to specify an array. To change a certain value, just assign a new value to it.
If you want to remove a key/value pair, you need to it. Przyk³ad 6-4. Using array // Array as (property-)map $map = array( 'version' = 4, 'OS' = 'Linux', 'lang' = 'english', 'shorttags' = true ); // strictly numerical keys $array = array( 7, 8, 0, 156, -10 ); // this is the same as array( 0 = 7, 1 = 8.) $switching = array( 10 // key = 0, 5 = 6, 3 = 7, 'a' = 4, 11 // key = 6 (maximum of integer-indices was 5), '8' = 2 // key = 8 (integer!), '02' = 77 // key = '02', 0 = 12 // the value 10 will be overwritten by 12 ); // empty array $empty = array. PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which that variable is used. That is to say, if you assign a string value to variable var, var becomes a string. If you then assign an integer value to var, it becomes an integer.
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An example of PHP's automatic type conversion is the addition operator '+'. If any of the operands is a float, then all operands are evaluated as floats, and the result will be a float.
Otherwise, the operands will be interpreted as integers, and the result will also be an integer. Note that this does NOT change the types of the operands themselves; the only change is in how the operands are evaluated.
$foo = '0'; // $foo is string (ASCII 48) $foo += 2; // $foo is now an integer (2) $foo = $foo + 1.3; // $foo is now a float (3.3) $foo = 5 + '10 Little Piggies'; // $foo is integer (15) $foo = 5 + '10 Small Pigs'; // $foo is integer (15) If the last two examples above seem odd, see. If you wish to force a variable to be evaluated as a certain type, see the section on. If you wish to change the type of a variable, see.
If you would like to test any of the examples in this section, you can use the function.