35 lines
1.8 KiB
Markdown
35 lines
1.8 KiB
Markdown
# Forked IP address parsing functions
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This directory contains a subset of code from the Go project's `net` package
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as of Go 1.16, used under the Go project license which we've included here
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in [`LICENSE`](LICENSE) and [`PATENTS`](PATENTS), which are also copied from
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the Go project.
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Terraform has its own fork of these functions because Go 1.17 included a
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breaking change to reject IPv4 address octets written with leading zeros.
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The Go project rationale for that change was that Go historically interpreted
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leading-zero octets inconsistently with many other implementations, trimming
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off the zeros and still treating the rest as decimal rather than treating the
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octet as octal.
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The Go team made the reasonable observation that having a function that
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interprets a non-normalized form in a manner inconsistent with other
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implementations may cause naive validation or policy checks to produce
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incorrect results, and thus it's a potential security concern. For more
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information, see [Go issue #30999](https://golang.org/issue/30999).
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After careful consideration, the Terraform team has concluded that Terraform's
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use of these functions as part of the implementation of the `cidrhost`,
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`cidrsubnet`, `cidrsubnets`, and `cidrnetmask` functions has a more limited
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impact than the general availability of these functions in the Go standard
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library, and so we can't justify a similar exception to our Terraform 1.0
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compatibility promises as the Go team made to their Go 1.0 compatibility
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promises.
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If you're considering using this package for new functionality _other than_ the
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built-in functions mentioned above, please do so only if consistency with the
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behavior of those functions is important. Otherwise, new features are not
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burdened by the same compatibility constraints and so should typically prefer
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to use the stricter interpretation of the upstream parsing functions.
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