17 Security Guards

▼ |  | Inside: Racket C API

1 | Overview
2 | Embedding into a Program
3 | Writing Racket Extensions
4 | Values and Types
5 | Memory Allocation
6 | Namespaces and Modules
7 | Procedures
8 | Evaluation
9 | Exceptions and Escape Continuations
10 | Threads
11 | Parameterizations
12 | Continuation Marks
13 | String Encodings
14 | Bignums, Rationals, and Complex Numbers
15 | Ports and the Filesystem
16 | Structures
17 | Security Guards
18 | Custodians
19 | Subprocesses
20 | Miscellaneous Utilities
| Index

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### 17`` Security Guards

Before a primitive procedure accesses the filesystem or creates a network connection, it should first consult the current security guard to determine whether such access is allowed for the current thread.

File access is normally preceded by a call to scheme_expand_filename, which accepts flags to indicate the kind of filesystem access needed, so that the security guard is consulted automatically.

An explicit filesystem-access check can be made by calling scheme_security_check_file. Similarly, an explicit network-access check is performed by calling scheme_security_check_network.

void |  | scheme_security_check_file | ( | const char* who,
|  |  |  | char* filename,
|  |  |  | int guards)

Consults the current security manager to determine whether access is allowed to filename. The guards argument should be a bitwise combination of the following:

- SCHEME_GUARD_FILE_READ

- SCHEME_GUARD_FILE_WRITE

- SCHEME_GUARD_FILE_EXECUTE

- SCHEME_GUARD_FILE_DELETE

- SCHEME_GUARD_FILE_EXISTS (do not combine with other values)

The filename argument can be NULL (in which case #f is sent to the security manager’s procedure), and guards should be SCHEME_GUARD_FILE_EXISTS in that case.

If access is denied, an exception is raised.

void |  | scheme_security_check_network | ( | const char* who,
|  |  |  | char* host,
|  |  |  | int portno)

Consults the current security manager to determine whether access is allowed for creating a client connection to host on port number portno. If host is NULL, the security manager is consulted for creating a server at port number portno.

If access is denied, an exception is raised.

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