Fix hostkey being too short

Modern versions of ssh refuse to connect to a server with a rsa key that is less than 2048 and this may change to 3072 or 4096 in the future. ed25519 cannot change keysize
cmd/breakglass: fallback to HTTP instead of detecting stripping
2025-12-28 13:12:09 -08:00 · 2025-12-09 17:22:34 +01:00 · 2025-12-05 17:50:59 +01:00 · 2025-12-05 17:34:49 +01:00 · 2025-11-20 07:37:04 +01:00
4 changed files with 36 additions and 51 deletions
--- a/breakglass.go
+++ b/breakglass.go
@@ -6,8 +6,8 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"crypto/ed25519"
 	"crypto/rand"
-	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
 	"flag"
@@ -91,7 +91,7 @@ func loadHostKey(path string) (ssh.Signer, error) {
 }

 func createHostKey(path string) (ssh.Signer, error) {
-	key, err := rsa.GenerateKey(rand.Reader, 1024)
+	_, key, err := ed25519.GenerateKey(rand.Reader)
 	if err != nil {
 		return nil, err
 	}
--- a/cmd/breakglass/breakglass.go
+++ b/cmd/breakglass/breakglass.go
@@ -26,7 +26,6 @@ import (
 	"github.com/gokrazy/internal/config"
 	"github.com/gokrazy/internal/httpclient"
 	"github.com/gokrazy/internal/instanceflag"
-	"github.com/gokrazy/internal/tlsflag"
 	"github.com/gokrazy/internal/updateflag"
 )

@@ -35,9 +34,11 @@ type bg struct {
 	cfg          *config.Struct
 	forceRestart bool
 	sshConfig    string
+	insecure     bool

 	// state
 	GOARCH string
+	update updateflag.Value
 }

 func (bg *bg) startBreakglass() error {
@@ -46,37 +47,28 @@ func (bg *bg) startBreakglass() error {
 		return err
 	}

-	updateHttpClient, foundMatchingCertificate, updateBaseURL, err := httpclient.For(bg.cfg)
+	updateHttpClient, _, updateBaseURL, err := httpclient.For(bg.update, bg.cfg)
 	if err != nil {
 		return err
 	}
 	updateHttpClient.Jar = jar

-	remoteScheme, err := httpclient.GetRemoteScheme(updateBaseURL)
-	if remoteScheme == "https" && !tlsflag.Insecure() {
-		updateBaseURL.Scheme = "https"
-		updateflag.SetUpdate(updateBaseURL.String())
-	}
-
-	if updateBaseURL.Scheme != "https" && foundMatchingCertificate {
-		fmt.Printf("\n")
-		fmt.Printf("!!!WARNING!!! Possible SSL-Stripping detected!\n")
-		fmt.Printf("Found certificate for hostname in your client configuration but the host does not offer https!\n")
-		fmt.Printf("\n")
-		if !tlsflag.Insecure() {
-			log.Fatalf("update canceled: TLS certificate found, but negotiating a TLS connection with the target failed")
-		}
-		fmt.Printf("Proceeding anyway as requested (-insecure).\n")
-	}
-
+	form, err := updateHttpClient.Get(updateBaseURL.String() + "status?path=/user/breakglass")
+	if err != nil {
+		if updateBaseURL.Scheme == "https" && bg.insecure {
+			// Try falling back to HTTP
+			bg.cfg.Update.UseTLS = "off"
+			updateHttpClient, _, updateBaseURL, err = httpclient.For(bg.update, bg.cfg)
 			if err != nil {
 				return err
 			}
-
-	form, err := updateHttpClient.Get(updateBaseURL.String() + "status?path=/user/breakglass")
+			form, err = updateHttpClient.Get(updateBaseURL.String() + "status?path=/user/breakglass")
 			if err != nil {
 				return err
 			}
+		}
+		return err
+	}
 	if form.StatusCode == http.StatusNotFound {
 		fmt.Fprintf(os.Stderr, "Hint: have you installed Go package github.com/gokrazy/breakglass on your gokrazy instance %q?\n", bg.cfg.Hostname)
 	}
@@ -198,6 +190,11 @@ func breakglass() error {
 			false,
 			"prepare the SSH connection only, but do not execute SSH (useful for using breakglass within an SSH ProxyCommand)")

+		insecure = flag.Bool(
+			"insecure",
+			false,
+			"Fall back to HTTP if HTTPS is configured, but does not work.")
+
 		proxy = flag.Bool(
 			"proxy",
 			false,
@@ -209,13 +206,6 @@ func breakglass() error {
 			"an alternative per-user configuration file for ssh and scp")
 	)

-	// TODO: remove the -tls and -gokrazy_url flags after 2023-June (half a year
-	// after the introduction of instance centric config), so that we can then
-	// merge these flags into tools/internal/oldpacker and remove their global
-	// state.
-	tlsflag.RegisterFlags(flag.CommandLine)
-	updateflag.RegisterFlags(flag.CommandLine, "gokrazy_url")
-
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr, "Usage of %s:\n\n", os.Args[0])

@@ -231,13 +221,6 @@ func breakglass() error {
 		log.Fatalf("syntax: breakglass <hostname> [command]")
 	}

-	// If the user did not explicitly specify -update=yes, we default to it.
-	// This differs from the gokr-packer, but breakglass is only useful for
-	// gokrazy instances that already exist.
-	if updateflag.NewInstallation() {
-		updateflag.SetUpdate("yes")
-	}
-
 	instance := flag.Arg(0)
 	instanceflag.SetInstance(instance)

@@ -255,6 +238,8 @@ func breakglass() error {
 		cfg:          cfg,
 		forceRestart: *forceRestart,
 		sshConfig:    *sshConfig,
+		insecure:     *insecure,
+		update:       updateflag.Value{Update: "yes"},
 	}
 	if cfg.Update.Hostname == "" {
 		cfg.Update.Hostname = cfg.Hostname
--- a/go.mod
+++ b/go.mod
@@ -1,16 +1,16 @@
 module github.com/gokrazy/breakglass

-go 1.24
+go 1.24.0

 require (
 	github.com/gokrazy/gokapi v0.0.0-20250222071133-506fdb322775
 	github.com/gokrazy/gokrazy v0.0.0-20250222061409-bd0bb5f1d0b5
-	github.com/gokrazy/internal v0.0.0-20250214203001-b1610a6e7271
+	github.com/gokrazy/internal v0.0.0-20251208203110-3c1aa9087c82
 	github.com/google/renameio/v2 v2.0.0
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/kr/pty v1.1.8
 	github.com/pkg/sftp v1.13.5
-	golang.org/x/crypto v0.35.0
+	golang.org/x/crypto v0.45.0
 )

 require (
@@ -20,5 +20,5 @@ require (
 	github.com/mdlayher/watchdog v0.0.0-20221003142519-49be0df7b3b5 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	golang.org/x/oauth2 v0.27.0 // indirect
-	golang.org/x/sys v0.30.0 // indirect
+	golang.org/x/sys v0.38.0 // indirect
 )
--- a/go.sum
+++ b/go.sum
@@ -7,8 +7,8 @@ github.com/gokrazy/gokapi v0.0.0-20250222071133-506fdb322775 h1:f5+2UMRRbr3+e/gd
 github.com/gokrazy/gokapi v0.0.0-20250222071133-506fdb322775/go.mod h1:q9mIV8al0wqmqFXJhKiO3SOHkL9/7Q4kIMynqUQWhgU=
 github.com/gokrazy/gokrazy v0.0.0-20250222061409-bd0bb5f1d0b5 h1:VQhDGxRliP4ZTQ8+33v4VKtOpX4VzN8pA4zBMZQSSxs=
 github.com/gokrazy/gokrazy v0.0.0-20250222061409-bd0bb5f1d0b5/go.mod h1:6fAh0J7aH6o5HWSiwN6uxNlm6Rjx1BxeNMWyNBQZ6sI=
-github.com/gokrazy/internal v0.0.0-20250214203001-b1610a6e7271 h1:CG2P/McW77phMh+iUSsGweJd4VwGhGS4UQJ92gV7Ihg=
-github.com/gokrazy/internal v0.0.0-20250214203001-b1610a6e7271/go.mod h1:vvnvmAv/38qDCHJ9b6Bq7yvUap6DcGtjZWjGuv/RA1k=
+github.com/gokrazy/internal v0.0.0-20251208203110-3c1aa9087c82 h1:4ghNfD9NaZLpFrqQiBF6mPVFeMYXJSky38ubVA4ic2E=
+github.com/gokrazy/internal v0.0.0-20251208203110-3c1aa9087c82/go.mod h1:dQY4EMkD4L5ZjYJ0SPtpgYbV7MIUMCxNIXiOfnZ6jP4=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/renameio/v2 v2.0.0 h1:UifI23ZTGY8Tt29JbYFiuyIU3eX+RNFtUwefq9qAhxg=
@@ -33,8 +33,8 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 golang.org/x/crypto v0.0.0-20211215153901-e495a2d5b3d3/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
-golang.org/x/crypto v0.35.0 h1:b15kiHdrGCHrP6LvwaQ3c03kgNhhiMgvlhxHQhmg2Xs=
-golang.org/x/crypto v0.35.0/go.mod h1:dy7dXNW32cAb/6/PRuTNsix8T+vJAqvuIy5Bli/x0YQ=
+golang.org/x/crypto v0.45.0 h1:jMBrvKuj23MTlT0bQEOBcAE0mjg8mK9RXFhRH6nyF3Q=
+golang.org/x/crypto v0.45.0/go.mod h1:XTGrrkGJve7CYK7J8PEww4aY7gM3qMCElcJQ8n8JdX4=
 golang.org/x/net v0.0.0-20211112202133-69e39bad7dc2/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/oauth2 v0.27.0 h1:da9Vo7/tDv5RH/7nZDz1eMGS/q1Vv1N/7FCrBhI9I3M=
 golang.org/x/oauth2 v0.27.0/go.mod h1:onh5ek6nERTohokkhCD/y2cV4Do3fxFHFuAejCkRWT8=
@@ -42,11 +42,11 @@ golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
-golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
+golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.29.0 h1:L6pJp37ocefwRRtYPKSWOWzOtWSxVajvz2ldH/xi3iU=
-golang.org/x/term v0.29.0/go.mod h1:6bl4lRlvVuDgSf3179VpIxBF0o10JUpXWOnI7nErv7s=
+golang.org/x/term v0.37.0 h1:8EGAD0qCmHYZg6J17DvsMy9/wJ7/D/4pV/wfnld5lTU=
+golang.org/x/term v0.37.0/go.mod h1:5pB4lxRNYYVZuTLmy8oR2BH8dflOR+IbTYFD8fi3254=
 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=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
Author	SHA1	Message	Date
Timmy Welch	8f5bdaed8a	Fix hostkey being too short Some checks failed Push / CI (push) Has been cancelled Details Modern versions of ssh refuse to connect to a server with a rsa key that is less than 2048 and this may change to 3072 or 4096 in the future. ed25519 cannot change keysize	2025-12-28 13:12:09 -08:00
Michael Stapelberg	3d571d9ebb	cmd/breakglass: fallback to HTTP instead of detecting stripping This follows gokrazy/tools commit `ba6a8936f4`	2025-12-09 17:22:34 +01:00
Michael Stapelberg	e8f40f784b	cmd/breakglass: use updateflag.Value, add own -insecure flag related to https://github.com/gokrazy/tools/pull/68	2025-12-05 17:50:59 +01:00
Michael Stapelberg	e4167a5b08	cmd/breakglass: remove old -gokrazy_url and -tls flags These have been deprecated for years. All users should have switched to the instance-centric config by now. related to https://github.com/gokrazy/tools/pull/68	2025-12-05 17:34:49 +01:00
dependabot[bot]	596b54e033	Bump golang.org/x/crypto from 0.35.0 to 0.45.0 (#26 ) Bumps [golang.org/x/crypto](https://github.com/golang/crypto) from 0.35.0 to 0.45.0. - [Commits](https://github.com/golang/crypto/compare/v0.35.0...v0.45.0) --- updated-dependencies: - dependency-name: golang.org/x/crypto dependency-version: 0.45.0 dependency-type: direct:production ... Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>	2025-11-20 07:37:04 +01:00