Update sshj to 0.30.0 and improve algorithm order (#1026)

Updates sshj to 0.30.0, which brings support for rsa-sha2-* key types
and bugfixes related to RSA certificates and Android Keystore backed
keys.

Along the way, this improves the algorithm preferences to be consistent
with the Mozilla Intermediate SSH configuration (as far as possible,
given that most certificate types and some encryption algorithms are
not yet supported).

We also add "ext-info-c" to the kex algorithm proposal to work around
certain kinds of "user agent sniffing" that limits the support of
rsa-sha2-* key types.

1 files changed, 20 insertions, 17 deletions

diff --git a/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt
index 1ea0359c..6c409329 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt
@@ -6,17 +6,15 @@ package com.zeapo.pwdstore.git.config
 
 import com.github.ajalt.timberkt.Timber
 import com.github.ajalt.timberkt.d
-import com.hierynomus.sshj.signature.SignatureEdDSA
+import com.hierynomus.sshj.key.KeyAlgorithms
 import com.hierynomus.sshj.transport.cipher.BlockCiphers
+import com.hierynomus.sshj.transport.kex.ExtInfoClientFactory
 import com.hierynomus.sshj.transport.mac.Macs
 import com.hierynomus.sshj.userauth.keyprovider.OpenSSHKeyV1KeyFile
 import java.security.Security
 import net.schmizz.keepalive.KeepAliveProvider
 import net.schmizz.sshj.ConfigImpl
 import net.schmizz.sshj.common.LoggerFactory
-import net.schmizz.sshj.signature.SignatureECDSA
-import net.schmizz.sshj.signature.SignatureRSA
-import net.schmizz.sshj.signature.SignatureRSA.FactoryCERT
 import net.schmizz.sshj.transport.compression.NoneCompression
 import net.schmizz.sshj.transport.kex.Curve25519SHA256
 import net.schmizz.sshj.transport.kex.Curve25519SHA256.FactoryLibSsh
@@ -202,7 +200,7 @@ class SshjConfig : ConfigImpl() {
         version = "OpenSSH_8.2p1 Ubuntu-4ubuntu0.1"
 
         initKeyExchangeFactories()
-        initSignatureFactories()
+        initKeyAlgorithms()
         initRandomFactory()
         initFileKeyProviderFactories()
         initCipherFactories()
@@ -218,17 +216,22 @@ class SshjConfig : ConfigImpl() {
             ECDHNistP.Factory384(),
             ECDHNistP.Factory256(),
             DHGexSHA256.Factory(),
+            // Sends "ext-info-c" with the list of key exchange algorithms. This is needed to get
+            // rsa-sha2-* key types to work with some servers (e.g. GitHub).
+            ExtInfoClientFactory(),
         )
     }
 
-    private fun initSignatureFactories() {
-        signatureFactories = listOf(
-            SignatureEdDSA.Factory(),
-            SignatureECDSA.Factory256(),
-            SignatureECDSA.Factory384(),
-            SignatureECDSA.Factory521(),
-            SignatureRSA.Factory(),
-            FactoryCERT(),
+    private fun initKeyAlgorithms() {
+        keyAlgorithms = listOf(
+            KeyAlgorithms.SSHRSACertV01(),
+            KeyAlgorithms.EdDSA25519(),
+            KeyAlgorithms.RSASHA512(),
+            KeyAlgorithms.RSASHA256(),
+            KeyAlgorithms.ECDSASHANistp521(),
+            KeyAlgorithms.ECDSASHANistp384(),
+            KeyAlgorithms.ECDSASHANistp256(),
+            KeyAlgorithms.SSHRSA(),
         )
     }
 
@@ -249,18 +252,18 @@ class SshjConfig : ConfigImpl() {
 
     private fun initCipherFactories() {
         cipherFactories = listOf(
-            BlockCiphers.AES128CTR(),
-            BlockCiphers.AES192CTR(),
             BlockCiphers.AES256CTR(),
+            BlockCiphers.AES192CTR(),
+            BlockCiphers.AES128CTR(),
         )
     }
 
     private fun initMACFactories() {
         macFactories = listOf(
-            Macs.HMACSHA2256(),
+            Macs.HMACSHA2512Etm(),
             Macs.HMACSHA2256Etm(),
             Macs.HMACSHA2512(),
-            Macs.HMACSHA2512Etm(),
+            Macs.HMACSHA2256(),
         )
     }