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gleroi opened this issue Mar 17, 2017 · 7 comments
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crypto/cipher: aesGcm: customize the size of the Tag #19594

gleroi opened this issue Mar 17, 2017 · 7 comments
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FrozenDueToAge help wanted NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.11

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@gleroi
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gleroi commented Mar 17, 2017 •
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What did you do?

https://play.golang.org/p/3lHakDk4WV

i'm working on AES GCM encrypted data from the DLMS/Cosem protocol.
This protocol use AES GCM 128 bits but only keep the 12 bytes of the tag

I you look in the code of crypto/cipher/gcm.go:gcm.Open, you'll see that the 12 leftmost bytes are identical, i just need a way to limit the comparison to 12 bytes.

What did you expect to see?

I expect to be able to configure the size of the tag.

System details

go version go1.8 windows/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=".exe"
GOHOSTARCH="amd64"
GOHOSTOS="windows"
GOOS="windows"
GOPATH="D:\Projets\go"
GORACE=""
GOROOT="D:\Go"
GOTOOLDIR="D:\Go\pkg\tool\windows_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\GL262BEN\AppData\Local\Temp\go-build100801603=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
GOROOT/bin/go version: go version go1.8 windows/amd64
GOROOT/bin/go tool compile -V: compile version go1.8 X:framepointer
gdb --version: GNU gdb (GDB) 7.6.1
@bradfitz bradfitz added the NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. label Mar 17, 2017
@bradfitz
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To @agl for decision.

@bradfitz bradfitz added this to the Go1.9 milestone Mar 21, 2017
@agl
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agl commented Mar 24, 2017

This is a reasonable request. The different tag size should be exposed as a different AEAD, i.e. something like NewGCMWithTagSize.

@bradfitz bradfitz added NeedsFix The path to resolution is known, but the work has not been done. help wanted and removed NeedsDecision Feedback is required from experts, contributors, and/or the community before a change can be made. labels Mar 24, 2017
@gleroi
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gleroi commented Mar 25, 2017

Im going to look at the contributor guidelines to propose a pull request on monday if it is ok.

@gopherbot
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CL https://golang.org/cl/38691 mentions this issue.

@bradfitz
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The CL mailed above doesn't compile, so bumping this to Go 1.10.

@bradfitz bradfitz modified the milestones: Go1.10, Go1.9 Jun 13, 2017
@conradoplg
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I had a shot at this in a new CL (I was not sure if I could/should change the other one).

@gopherbot
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CL https://golang.org/cl/48510 mentions this issue.

@bradfitz bradfitz modified the milestones: Go1.10, Unplanned Nov 10, 2017
@FiloSottile FiloSottile modified the milestones: Unplanned, Go1.11 Feb 10, 2018
@joelthompson joelthompson mentioned this issue Mar 26, 2018
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@golang golang locked and limited conversation to collaborators Feb 14, 2019
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Go1.11
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@bradfitz @agl @conradoplg @gleroi @FiloSottile @gopherbot