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refactor sshfx encoding, fix link rot, go fmt #545

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merged 2 commits into from
Apr 1, 2023

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puellanivis
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I’ve poked around with the wire formatting code, and switched from a “check error every time” to “accumulate an error” which allows for more direct and concise unmarshals in general.

Also, I found the ietf draft link rot #544 and updated each of the ones that points to a version earlier than -13. (The -13 links are still valid.)

Also, we’ve accumulated some go fmt changes that show up in go 1.20, so I threw those in as well.

Comment on lines +55 to +57
*b = Buffer{
b: b.b[:0],
}
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This syntax clears off and Err implicitly.

if b.Len() < 1 {
return 0, ErrShortPacket
b.off = len(b.b)
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We set the b.off to len(b.b) before every b.Err = ErrShortPacket so that say, we’re unmarshalling a uint32, and that fails because there are only 3 bytes left, but then we unmarshal a uint8, which would succeed and consume one of the three remaining bytes.

We also if b.Err != nil { … } as preamble of each Consume… function, but it’s better to have safety in layers, rather than rely on only one single failsafe.

}

v := b.b[b.off:]
if len(v) > int(length) {
if len(v) > length || cap(v) > length {
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I realized, we should ensure the cap is clamped the same as len.

//
// If hint has sufficient capacity to hold the data, it will be reused and overwritten,
// otherwise a new backing slice will be allocated and returned.
func (b *Buffer) ConsumeByteSliceCopy(hint []byte) []byte {
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@puellanivis puellanivis Mar 27, 2023

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Turns out, we were using this code twice, but it was also wholly reallocating if len was insufficient, even though maybe it has the available cap. So, using the grow slice trick instead, so maybe we have a chance to reuse hint even if the len is insufficient, but the cap is sufficient.

package filexfer
package sshfx
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Changing the expected name of this package, so that importers know the preferred name it should be renamed to.

@@ -122,3 +122,48 @@ func (f PacketType) String() string {
return fmt.Sprintf("SSH_FXP_UNKNOWN(%d)", f)
}
}

func newPacketFromType(typ PacketType) (Packet, error) {
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This function makes way more sense here, rather than in packets.go.

}

// ReadPacket defines the SSH_FXP_READ packet.
type ReadPacket struct {
Handle string
Offset uint64
Len uint32
Length uint32
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@puellanivis puellanivis Mar 27, 2023

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Name change to better mirror standard.

@@ -4,54 +4,54 @@ import (
sshfx "github.com/pkg/sftp/internal/encoding/ssh/filexfer"
)

const extensionPosixRename = "[email protected]"
const extensionPOSIXRename = "[email protected]"
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POSIX is an all-caps abbreviation that should be all-caps in variable names. (Are you glad we had this all in internal so we could change this bad early draft choice? :trollface: )

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@drakkan drakkan left a comment

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I took a quick look and it looks ok. I don't have time for a full review, sorry. In general I may reduce my involvement in open source in the coming months.

@puellanivis
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It’s ok. I’ve had to scale back from time to time as well. Especially, when a job comes in that doesn’t have a synergy with working on the project.

@puellanivis puellanivis merged commit 34d66dd into master Apr 1, 2023
@puellanivis puellanivis deleted the sshfx-refactor-and-fix-ietf-link-rot branch April 1, 2023 22:44
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2 participants