153 lines
2.5 KiB
HTML
153 lines
2.5 KiB
HTML
<HTML
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>Limit Call-outs to Valid Values</TITLE
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TITLE="Carefully Call Out to Other Resources"
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>Chapter 8. Carefully Call Out to Other Resources</TD
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NAME="LIMIT-CALL-OUTS"
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>8.2. Limit Call-outs to Valid Values</H1
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><P
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>Ensure that any call out to another program only permits valid
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and expected values for every parameter.
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This is more difficult than it sounds, because many
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library calls or commands call lower-level routines in potentially
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surprising ways.
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For example, many system calls are implemented indirectly by
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calling the shell, which means that passing characters which are shell
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metacharacters can have dangerous effects.
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So, let's discuss metacharacters.</P
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