Support identification string without carriage return

Sources/NIOSSH/SSHPacketParser.swift

@@ -112,13 +112,22 @@ struct SSHPacketParser {
     }
 
     private mutating func readVersion() throws -> String? {
-        // Looking for a string ending with \r\n
-        let slice = self.buffer.readableBytesView
-        if let cr = slice.firstIndex(of: 13), cr.advanced(by: 1) < slice.endIndex, slice[cr.advanced(by: 1)] == 10 {
-            let version = String(decoding: slice[slice.startIndex ..< cr], as: UTF8.self)
-            // read \r\n
-            self.buffer.moveReaderIndex(forwardBy: slice.startIndex.distance(to: cr).advanced(by: 2))
-            return version
+        let carriageReturn = UInt8(ascii: "\r")
+        let lineFeed = UInt8(ascii: "\n")
+
+        // Search for version line, which starts with "SSH-". Lines without this prefix may come before the version line.
+        var slice = self.buffer.readableBytesView
+        while let lfIndex = slice.firstIndex(of: lineFeed), lfIndex < slice.endIndex {
+            if slice.starts(with: "SSH-".utf8) {
+                // Return all data upto the last LF we found, excluding the last [CR]LF.
+                slice = self.buffer.readableBytesView
+                let versionEndIndex = slice[lfIndex.advanced(by: -1)] == carriageReturn ? lfIndex.advanced(by: -1) : lfIndex
+                let version = String(decoding: slice[slice.startIndex ..< versionEndIndex], as: UTF8.self)
+                self.buffer.moveReaderIndex(forwardBy: slice.startIndex.distance(to: lfIndex).advanced(by: 1))
+                return version
+            } else {
+                slice = slice[slice.index(after: lfIndex)...]
+            }
         }
         return nil
     }

Tests/NIOSSHTests/SSHPacketParserTests.swift

@@ -54,6 +54,63 @@ final class SSHPacketParserTests: XCTestCase {
         }
     }
 
+    func testReadVersionWithExtraLines() throws {
+        var parser = SSHPacketParser(allocator: ByteBufferAllocator())
+
+        var part1 = ByteBuffer.of(string: "xxxx\r\nyyyy\r\nSSH-2.0-")
+        parser.append(bytes: &part1)
+
+        XCTAssertNil(try parser.nextPacket())
+
+        var part2 = ByteBuffer.of(string: "OpenSSH_7.9\r\n")
+        parser.append(bytes: &part2)
+
+        switch try parser.nextPacket() {
+        case .version(let string):
+            XCTAssertEqual(string, "xxxx\r\nyyyy\r\nSSH-2.0-OpenSSH_7.9")
+        default:
+            XCTFail("Expecting .version")
+        }
+    }
+
+    func testReadVersionWithoutCarriageReturn() throws {
+        var parser = SSHPacketParser(allocator: ByteBufferAllocator())
+
+        var part1 = ByteBuffer.of(string: "SSH-2.0-")
+        parser.append(bytes: &part1)
+
+        XCTAssertNil(try parser.nextPacket())
+
+        var part2 = ByteBuffer.of(string: "OpenSSH_7.4\n")
+        parser.append(bytes: &part2)
+
+        switch try parser.nextPacket() {
+        case .version(let string):
+            XCTAssertEqual(string, "SSH-2.0-OpenSSH_7.4")
+        default:
+            XCTFail("Expecting .version")
+        }
+    }
+
+    func testReadVersionWithExtraLinesWithoutCarriageReturn() throws {
+        var parser = SSHPacketParser(allocator: ByteBufferAllocator())
+
+        var part1 = ByteBuffer.of(string: "xxxx\nyyyy\nSSH-2.0-")
+        parser.append(bytes: &part1)
+
+        XCTAssertNil(try parser.nextPacket())
+
+        var part2 = ByteBuffer.of(string: "OpenSSH_7.4\n")
+        parser.append(bytes: &part2)
+
+        switch try parser.nextPacket() {
+        case .version(let string):
+            XCTAssertEqual(string, "xxxx\nyyyy\nSSH-2.0-OpenSSH_7.4")
+        default:
+            XCTFail("Expecting .version")
+        }
+    }
+
     func testBinaryInParts() throws {
         var parser = SSHPacketParser(allocator: ByteBufferAllocator())
         self.feedVersion(to: &parser)