Closed
Description
What version of Go are you using (go version)?
$ go version go version go1.16.4 linux/amd64
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/home/samiponkanen/.cache/go-build" GOENV="/home/samiponkanen/.config/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/home/samiponkanen/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/home/samiponkanen/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/usr/local/lib/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/local/lib/go/pkg/tool/linux_amd64" GOVCS="" GOVERSION="go1.16.4" GCCGO="gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="1" GOMOD="/home/samiponkanen/src/github.com/samiponkanen/crypto/go.mod" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2597822555=/tmp/go-build -gno-record-gcc-switches"
What did you do?
Use Tectia SSH client with RSA publickey authentication to connect to ssh server using the golang.org/x/crypto/ssh package. This results into the following errors in ssh.ServerConfig.AuthLogCallback():
2021/06/04 13:11:32 [ERROR] client-auth.go:144 conn ec66cf06-3dc4-49f7-67e0-e1cb9e6fbeb1: auth user 'root' local '172.23.0.21:2222' remote '192.168.200.101:45110' client-version 'SSH-2.0-6.4.19.367 SSH Secure Shell' server-version 'SSH-2.0-Go' session-id db28a8ab840ffc68684be3974c7a001a4f547806 error: ssh: algorithm "rsa-sha2-256" not accepted 2021/06/04 13:11:32 [ERROR] client-auth.go:144 conn ec66cf06-3dc4-49f7-67e0-e1cb9e6fbeb1: auth user 'root' local '172.23.0.21:2222' remote '192.168.200.101:45110' client-version 'SSH-2.0-6.4.19.367 SSH Secure Shell' server-version 'SSH-2.0-Go' session-id db28a8ab840ffc68684be3974c7a001a4f547806 error: ssh: algorithm "rsa-sha2-512" not accepted
Modifying unit test TestClientAuthPublicKey() in ssh/client_auth_test.go to sign using "rsa-sha2-256" or "rsa-sha2-512" algorithm causes the unit test to fail:
$ go test -v -run ^TestClientAuthPublicKey
=== RUN TestClientAuthPublicKey
client_auth_test.go:117: unable to dial remote side: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain
--- FAIL: TestClientAuthPublicKey (0.01s)
FAIL
exit status 1
FAIL golang.org/x/crypto/ssh 0.043s
Adding SigAlgoRSASHA2256 and SigAlgoRSASHA2512 to isAcceptableAlgo() fixes the problem.
What did you expect to see?
Expected ssh server to accept rsa-sha2-256 and rsa-sha2-512 signatures.
What did you see instead?
Ssh server rejects rsa-sha2-256 and rsa-sha2-512 in user auth message's public key algorithm name and signature format fields.