Abstracts - 12th Systems Administration Conference
Using Content-Derived Names for Package Management in Tcl
Ethan L. Miller and Kennedy Akala
University of Maryland Baltimore County
Jeffrey K. Hollinsworth
University of Maryland, College Park
Managing different versions of library routines has long
been a problem, both for Tcl and for other languages
that permit code reuse and modification (i.e., all computer
languages that the authors are aware of). This
problem is particularly difficult for Tcl because it allows
libraries (in the form of packages) to be dynamically
loaded as needed. While this feature is very convenient
- users need only keep a single copy of each library to
use it in many programs - it can lead to code compatibility
and distribution problems.
This paper presents a solution for this problem - using
content-derived names (CDNs) to name Tcl packages.
Using this solution, a program can simultaneously use
two different versions of a single package. In addition,
the Tcl interpreter can easily find instances of a missing
package over the network and download them, making
them available to a running application. Because content-
derived names are computed using a cryptographically
strong hash over the text of a package, this process
is safe from spoofing and other attacks based on providing
the wrong library. Thus, a user may download missing
packages from any server willing to provide them
without fear of virus or trojan horse attacks.
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