---
name: "libval_shim"
section: "3"
platform: "linux"
package: "dnssec-tools"
version: "2.2.3-16"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/libval_shim"
---

# libval\_shim(3)

## NAME

```
                      The Validator Shim Library
```

## DESCRIPTION

The validator shim library (*libval\_shim.so*) is a shared library designed to be dynamically loaded using the 'LD\_PRELOAD' mechanism (*[ld.so(8)](/ld.so/8.md)*) supported on linux and various other unix-like platforms. The shim library implements wrappers for a number of DNS related functions and in turn calls equivalent DNSSEC-aware validating functions from *[libval(3)](/libval/3.md)*, mapping the results to return codes recognized by the original functions. In this way a wide variety of applications can be made DNSSEC aware without code changes and recompilation.

The method of mapping return codes assumes that any 'untrusted' or failure result from the *[libval(3)](/libval/3.md)* function is reflected as a failure to the original calling function.

### *Usage:*

To load the library set LD\_PRELOAD variable within the environment of the the target application prior to execution:

### *Validation Policy:*

The validator shim library will create a policy context and cache it for all subsequent *[libval(3)](/libval/3.md)* calls. A *NULL* policy label will be passed to create the context. The policy is chosen according to rules defined for *[libval(3)](/libval/3.md)*.

See *dnsval.conf(1)* for information on policy labels and definition.

### *Logging:*

Logging for the *[libval(3)](/libval/3.md)* functions may be enabled in the shim library by setting an environment variable.

See *[dt-validate(1)](/dt-validate/1.md)* for specifics.

## NOTES

### setuid/setgid programs

setuid and setgid root programs (e.g., *[ping(8)](/ping/8.md)*) do not honor the LD\_PRELOAD setting. These application may still use the LD\_PRELOAD mechanism when run directly from a root shell.

## COPYRIGHT

Copyright 2004-2013 SPARTA, Inc.  All rights reserved. See the COPYING file included with the dnssec-tools package for details.

## AUTHORS

G. S. Marzot

## SEE ALSO

*[libsres(3)](/libsres/3.md)*, *[libval(3)](/libval/3.md)*, *dnsval.conf(1)*, *[gethostbyname(3)](/gethostbyname/3.md)*

*[gethostbyaddr(3)](/gethostbyaddr/3.md)*, *[getnameinfo(3)](/getnameinfo/3.md)*, *[getaddrinfo(3)](/getaddrinfo/3.md)*, *[res\_query(3)](/res_query/3.md)*