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Fine tune ssh related comments and code #32846

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Merged
merged 2 commits into from
Dec 15, 2024
Merged

Fine tune ssh related comments and code #32846

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2235837
fix
wxiaoguang Dec 15, 2024
0265df4
Merge branch 'main' into improve-ssh-perm
wxiaoguang Dec 15, 2024
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12 changes: 6 additions & 6 deletions modules/ssh/ssh.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,6 @@ import (
"errors"
"fmt"
"io"
"maps"
"net"
"os"
"os/exec"
Expand Down Expand Up @@ -49,6 +48,10 @@ import (
// Then sessionHandler should only use the "verified keyID" from the original ssh conn, but not the ctx one.
// Otherwise, if a user provides 2 keys A (a correct one) and B (public key matches but no private key),
// then only A succeeds to authenticate, sessionHandler will see B's keyID
//
// After x/crypto >= 0.31.0 (fix CVE-2024-45337), the PublicKeyCallback will be called again for the verified key,
// it mitigates the misuse for most cases, it's still good for us to make sure we don't rely on that mitigation
// and do not misuse the PublicKeyCallback: we should only use the verified keyID from the verified ssh conn.

const giteaPermissionExtensionKeyID = "gitea-perm-ext-key-id"

Expand Down Expand Up @@ -100,8 +103,8 @@ func ptr[T any](intf any) *T {
func sessionHandler(session ssh.Session) {
// here can't use session.Permissions() because it only uses the value from ctx, which might not be the authenticated one.
// so we must use the original ssh conn, which always contains the correct (verified) keyID.
sshConn := ptr[sessionPartial](session)
keyID := sshConn.conn.Permissions.Extensions[giteaPermissionExtensionKeyID]
sshSession := ptr[sessionPartial](session)
keyID := sshSession.conn.Permissions.Extensions[giteaPermissionExtensionKeyID]

command := session.RawCommand()

Expand Down Expand Up @@ -210,10 +213,7 @@ func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {

// first, reset the ctx permissions (just like https://github.com/gliderlabs/ssh/pull/243 does)
// it shouldn't be reused across different ssh conn (sessions), each pub key should have its own "Permissions"
oldCtxPerm := ctx.Permissions().Permissions
ctx.Permissions().Permissions = &gossh.Permissions{}
ctx.Permissions().Permissions.CriticalOptions = maps.Clone(oldCtxPerm.CriticalOptions)

setPermExt := func(keyID int64) {
ctx.Permissions().Permissions.Extensions = map[string]string{
giteaPermissionExtensionKeyID: fmt.Sprint(keyID),
Expand Down
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