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| 1 | +From 041b89a18f81265899e42e6801f830c101a96120 Mon Sep 17 00:00:00 2001 |
| 2 | +From: Kanishk-Bansal < [email protected]> |
| 3 | +Date: Sun, 2 Mar 2025 13:46:00 +0000 |
| 4 | +Subject: [PATCH] CVE-2025-22869 |
| 5 | + |
| 6 | +Upstream Reference : https://github.com/golang/crypto/commit/7292932d45d55c7199324ab0027cc86e8198aa22 |
| 7 | + |
| 8 | +ssh: limit the size of the internal packet queue while waiting for KEX |
| 9 | + |
| 10 | +In the SSH protocol, clients and servers execute the key exchange to |
| 11 | +generate one-time session keys used for encryption and authentication. |
| 12 | +The key exchange is performed initially after the connection is |
| 13 | +established and then periodically after a configurable amount of data. |
| 14 | +While a key exchange is in progress, we add the received packets to an |
| 15 | +internal queue until we receive SSH_MSG_KEXINIT from the other side. |
| 16 | +This can result in high memory usage if the other party is slow to |
| 17 | +respond to the SSH_MSG_KEXINIT packet, or memory exhaustion if a |
| 18 | +malicious client never responds to an SSH_MSG_KEXINIT packet during a |
| 19 | +large file transfer. |
| 20 | +We now limit the internal queue to 64 packets: this means 2MB with the |
| 21 | +typical 32KB packet size. |
| 22 | +When the internal queue is full we block further writes until the |
| 23 | +pending key exchange is completed or there is a read or write error. |
| 24 | + |
| 25 | +Thanks to Yuichi Watanabe for reporting this issue. |
| 26 | + |
| 27 | +Change-Id: I1ce2214cc16e08b838d4bc346c74c72addafaeec |
| 28 | +Reviewed-on: https://go-review.googlesource.com/c/crypto/+/652135 |
| 29 | +Reviewed-by: Neal Patel < [email protected]> |
| 30 | +Auto-Submit: Gopher Robot < [email protected]> |
| 31 | +Reviewed-by: Roland Shoemaker < [email protected]> |
| 32 | +LUCI-TryBot-Result: Go LUCI < [email protected]> |
| 33 | + |
| 34 | +--- |
| 35 | + vendor/golang.org/x/crypto/ssh/handshake.go | 47 ++++++++++++++++----- |
| 36 | + 1 file changed, 37 insertions(+), 10 deletions(-) |
| 37 | + |
| 38 | +diff --git a/vendor/golang.org/x/crypto/ssh/handshake.go b/vendor/golang.org/x/crypto/ssh/handshake.go |
| 39 | +index 70a7369..e14eb6c 100644 |
| 40 | +--- a/vendor/golang.org/x/crypto/ssh/handshake.go |
| 41 | ++++ b/vendor/golang.org/x/crypto/ssh/handshake.go |
| 42 | +@@ -24,6 +24,11 @@ const debugHandshake = false |
| 43 | + // quickly. |
| 44 | + const chanSize = 16 |
| 45 | + |
| 46 | ++// maxPendingPackets sets the maximum number of packets to queue while waiting |
| 47 | ++// for KEX to complete. This limits the total pending data to maxPendingPackets |
| 48 | ++// * maxPacket bytes, which is ~16.8MB. |
| 49 | ++const maxPendingPackets = 64 |
| 50 | ++ |
| 51 | + // keyingTransport is a packet based transport that supports key |
| 52 | + // changes. It need not be thread-safe. It should pass through |
| 53 | + // msgNewKeys in both directions. |
| 54 | +@@ -58,11 +63,19 @@ type handshakeTransport struct { |
| 55 | + incoming chan []byte |
| 56 | + readError error |
| 57 | + |
| 58 | +- mu sync.Mutex |
| 59 | +- writeError error |
| 60 | +- sentInitPacket []byte |
| 61 | +- sentInitMsg *kexInitMsg |
| 62 | +- pendingPackets [][]byte // Used when a key exchange is in progress. |
| 63 | ++ mu sync.Mutex |
| 64 | ++ // Condition for the above mutex. It is used to notify a completed key |
| 65 | ++ // exchange or a write failure. Writes can wait for this condition while a |
| 66 | ++ // key exchange is in progress. |
| 67 | ++ writeCond *sync.Cond |
| 68 | ++ writeError error |
| 69 | ++ sentInitPacket []byte |
| 70 | ++ sentInitMsg *kexInitMsg |
| 71 | ++ // Used to queue writes when a key exchange is in progress. The length is |
| 72 | ++ // limited by pendingPacketsSize. Once full, writes will block until the key |
| 73 | ++ // exchange is completed or an error occurs. If not empty, it is emptied |
| 74 | ++ // all at once when the key exchange is completed in kexLoop. |
| 75 | ++ pendingPackets [][]byte |
| 76 | + writePacketsLeft uint32 |
| 77 | + writeBytesLeft int64 |
| 78 | + |
| 79 | +@@ -114,6 +127,7 @@ func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion, |
| 80 | + |
| 81 | + config: config, |
| 82 | + } |
| 83 | ++ t.writeCond = sync.NewCond(&t.mu) |
| 84 | + t.resetReadThresholds() |
| 85 | + t.resetWriteThresholds() |
| 86 | + |
| 87 | +@@ -236,6 +250,7 @@ func (t *handshakeTransport) recordWriteError(err error) { |
| 88 | + defer t.mu.Unlock() |
| 89 | + if t.writeError == nil && err != nil { |
| 90 | + t.writeError = err |
| 91 | ++ t.writeCond.Broadcast() |
| 92 | + } |
| 93 | + } |
| 94 | + |
| 95 | +@@ -339,6 +354,8 @@ write: |
| 96 | + } |
| 97 | + } |
| 98 | + t.pendingPackets = t.pendingPackets[:0] |
| 99 | ++ // Unblock writePacket if waiting for KEX. |
| 100 | ++ t.writeCond.Broadcast() |
| 101 | + t.mu.Unlock() |
| 102 | + } |
| 103 | + |
| 104 | +@@ -526,11 +543,20 @@ func (t *handshakeTransport) writePacket(p []byte) error { |
| 105 | + } |
| 106 | + |
| 107 | + if t.sentInitMsg != nil { |
| 108 | +- // Copy the packet so the writer can reuse the buffer. |
| 109 | +- cp := make([]byte, len(p)) |
| 110 | +- copy(cp, p) |
| 111 | +- t.pendingPackets = append(t.pendingPackets, cp) |
| 112 | +- return nil |
| 113 | ++ if len(t.pendingPackets) < maxPendingPackets { |
| 114 | ++ // Copy the packet so the writer can reuse the buffer. |
| 115 | ++ cp := make([]byte, len(p)) |
| 116 | ++ copy(cp, p) |
| 117 | ++ t.pendingPackets = append(t.pendingPackets, cp) |
| 118 | ++ return nil |
| 119 | ++ } |
| 120 | ++ for t.sentInitMsg != nil { |
| 121 | ++ // Block and wait for KEX to complete or an error. |
| 122 | ++ t.writeCond.Wait() |
| 123 | ++ if t.writeError != nil { |
| 124 | ++ return t.writeError |
| 125 | ++ } |
| 126 | ++ } |
| 127 | + } |
| 128 | + |
| 129 | + if t.writeBytesLeft > 0 { |
| 130 | +@@ -547,6 +573,7 @@ func (t *handshakeTransport) writePacket(p []byte) error { |
| 131 | + |
| 132 | + if err := t.pushPacket(p); err != nil { |
| 133 | + t.writeError = err |
| 134 | ++ t.writeCond.Broadcast() |
| 135 | + } |
| 136 | + |
| 137 | + return nil |
| 138 | +-- |
| 139 | +2.45.2 |
| 140 | + |
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