Reland "Add util/fetch_ech_config_list.go"

This is a reland of 160a8891ae9a1d03f29aec079a67d97bc773990e with go.mod
and go.sum fixed. This updates golang.org/x/crypto, adds the latest
golang.org/x/net as a direct dependency (it was previously an indirect
dependency via x/crypto), and cleans up stale entries from go.sum with
go mod tidy.

Original change's description:
> Add util/fetch_ech_config_list.go
>
> I wrote this tool to make it easier to test the ECH client against
> real-world servers with the bssl client tool. I found that manually
> extracting an ECHConfigList from a raw HTTPS record is unnecessarily
> painful.
>
> The tool queries DNS over UDP for HTTPS records. If it finds any HTTPS
> records in the response, it attempts to extract an ECHConfigList from
> the "ech" SvcParam. It can write each extracted ECHConfigList to a file
> in a given directory. Once the ECH client implementation lands, the bssl
> client tool should have a new flag that that takes the path to an
> ECHConfigList file.
>
> I am using golang.org/x/net/dns/dnsmessage to parse the DNS response. I
> recently added the |UnknownResource| type to this library to enable
> callers (like us) to extract the bytes of otherwise-unsupported records
> (like HTTPS). I updated the dependency with `go get -u golang.org/x/net`.
>
> Although the bssl client tool knows how to resolve the address of its
> "-connect" parameter, it is difficult to query HTTPS records in a
> platform-agnostic way. If we decide the bssl client should directly
> query HTTPS rather than leaning on fetch_ech_config_list.go, we should
> look into libresolv. Specifically, the |res_query| function enables the
> caller to query arbitrary record types. This may open its own can of
> cross-platform worms; macOS and Linux typically ship with different
> implementations and it is not available on Windows. For more info, see
> `man 3 resolver`.
>
> Bug: 275
> Change-Id: I705591658921f60a958164a18b68ffb697c2ea4b
> Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/44104
> Reviewed-by: David Benjamin <davidben@google.com>

Bug: 275
Change-Id: I9571e96c7a2ad7e239d86a353929a4e556d71287
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48106
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

1 files changed, 13 insertions, 8 deletions

diff --git a/go.sum b/go.sum
index 8b7d318..87e3c89 100644
--- a/go.sum
+++ b/go.sum
@@ -1,8 +1,13 @@
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9 h1:psW17arqaxU48Z5kZ0CQnkZWQJsqcURM6tKiBApRjXI=
-golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/crypto v0.0.0-20210513164829-c07d793c2f9a h1:kr2P4QFmQr29mSLA43kwrOcgcReGTfbE9N577tCTuBc=
+golang.org/x/crypto v0.0.0-20210513164829-c07d793c2f9a/go.mod h1:P+XmwS30IXTQdn5tA2iutPOUgjI07+tq3H3K9MVA1s8=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20210614182718-04defd469f4e h1:XpT3nA5TvE525Ne3hInMh6+GETgn27Zfm9dxsThnX2Q=
+golang.org/x/net v0.0.0-20210614182718-04defd469f4e/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210423082822-04245dca01da h1:b3NXsE2LusjYGGjL5bxEVZZORm/YEFFrWFjR8eFrw/c=
+golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1 h1:v+OssWQX+hTHEmOBgwxdZxK4zHq3yOs8F9J7mk0PY8E=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=