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ssh: ignore invalid MACs and KEXs just like we do for ciphers

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Tighter validation could cause backwards incompatibility issues, eg
configurations with valid and invalid MACs, KEXs, ciphers currently work
if a supported algorithm is negotiated and that's also the scenario of
removing support for an existing algorithm.

Fixes golang/go#39397

Change-Id: If90253ba89e1d8f732cc1e1c3d24fe0a1e2dac71
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/512175
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Nicola Murino
2023-07-31 15:35:32 +00:00
committed by Gopher Robot
parent d08e19beac
commit ddfa82138e
2 changed files with 113 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
ssh/common.go
+23 -7
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@@ -269,16 +269,16 @@ type Config struct {
// unspecified, a size suitable for the chosen cipher is used.
RekeyThreshold uint64
// The allowed key exchanges algorithms. If unspecified then a
// default set of algorithms is used.
// The allowed key exchanges algorithms. If unspecified then a default set
// of algorithms is used. Unsupported values are silently ignored.
KeyExchanges []string
// The allowed cipher algorithms. If unspecified then a sensible
// default is used.
// The allowed cipher algorithms. If unspecified then a sensible default is
// used. Unsupported values are silently ignored.
Ciphers []string
// The allowed MAC algorithms. If unspecified then a sensible default
// is used.
// The allowed MAC algorithms. If unspecified then a sensible default is
// used. Unsupported values are silently ignored.
MACs []string
}
@@ -295,7 +295,7 @@ func (c *Config) SetDefaults() {
var ciphers []string
for _, c := range c.Ciphers {
if cipherModes[c] != nil {
// reject the cipher if we have no cipherModes definition
// Ignore the cipher if we have no cipherModes definition.
ciphers = append(ciphers, c)
}
}
@@ -304,10 +304,26 @@ func (c *Config) SetDefaults() {
if c.KeyExchanges == nil {
c.KeyExchanges = preferredKexAlgos
}
var kexs []string
for _, k := range c.KeyExchanges {
if kexAlgoMap[k] != nil {
// Ignore the KEX if we have no kexAlgoMap definition.
kexs = append(kexs, k)
}
}
c.KeyExchanges = kexs
if c.MACs == nil {
c.MACs = supportedMACs
}
var macs []string
for _, m := range c.MACs {
if macModes[m] != nil {
// Ignore the MAC if we have no macModes definition.
macs = append(macs, m)
}
}
c.MACs = macs
if c.RekeyThreshold == 0 {
// cipher specific default