CWE-1272: Sensitive Information Uncleared Before Debug/Power State Transition

What is Sensitive Information Uncleared Before Debug/Power State Transition?

• Overview: This vulnerability occurs when a device or system transitions between different power or debug states without clearing sensitive information, potentially allowing unauthorized access to that information.

• Exploitation Methods:

• Attackers can exploit this by accessing residual sensitive data left in memory after a state transition.
• Common techniques include memory scraping during transitions or leveraging debug modes to retrieve sensitive data.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data such as credentials or personal information.
• Potential cascading effects include further system compromise due to exposed authentication tokens or keys.
• Business impact may involve data breaches leading to financial loss, reputational damage, and compliance violations.

• Prevention Guidelines:

• Specific code-level fixes include ensuring all sensitive data is explicitly cleared from memory before a state transition.
• Security best practices involve implementing strict data sanitization routines and validating state transitions.
• Recommended tools and frameworks may include memory management tools and hardware abstraction libraries that enforce data clearance policies.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: VHDL, Verilog, Hardware Description Language

Affected Technologies: Not Technology-Specific

Vulnerable Code Example

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity sensitive_memory is
    Port ( clk : in STD_LOGIC;
           reset : in STD_LOGIC;
           power_down : in STD_LOGIC;
           sensitive_data : inout STD_LOGIC_VECTOR (7 downto 0));
end sensitive_memory;

architecture Behavioral of sensitive_memory is
    signal internal_data : STD_LOGIC_VECTOR (7 downto 0);
begin
    process(clk, reset)
    begin
        if reset = '1' then
            internal_data <= (others => '0');
        elsif rising_edge(clk) then
            -- Vulnerable: sensitive data is not cleared on power down
            if power_down = '1' then
                -- No operation to clear sensitive data
                -- This leaves sensitive data in the register, which could be accessed during debug or after power state transitions
            else
                internal_data <= sensitive_data;
            end if;
        end if;
    end process;
end Behavioral;

Explanation

• In the above VHDL code, when the power_down signal is activated, the sensitive data (internal_data) is not cleared. This oversight leaves sensitive information in memory, which could be accessed during debugging or after power state transitions, posing a security risk.

How to fix Sensitive Information Uncleared Before Debug/Power State Transition?

To address this vulnerability, it is crucial to ensure that all sensitive information is cleared from memory before entering a low power or power-off state. This involves explicitly resetting or overwriting the memory containing sensitive data when a power-down mode or debug state transition is detected.

Best practices include:

• Explicitly zeroing out memory or overwriting it with non-sensitive data before power-down.
• Ensuring that sensitive information is not left in any registers or memory areas that could be accessed during debug or after a reset.

Fixed Code Example

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity sensitive_memory is
    Port ( clk : in STD_LOGIC;
           reset : in STD_LOGIC;
           power_down : in STD_LOGIC;
           sensitive_data : inout STD_LOGIC_VECTOR (7 downto 0));
end sensitive_memory;

architecture Behavioral of sensitive_memory is
    signal internal_data : STD_LOGIC_VECTOR (7 downto 0);
begin
    process(clk, reset)
    begin
        if reset = '1' then
            internal_data <= (others => '0');
        elsif rising_edge(clk) then
            if power_down = '1' then
                -- Secure: clear sensitive data during power down
                internal_data <= (others => '0');  -- Clear data to prevent leakage
            else
                internal_data <= sensitive_data;
            end if;
        end if;
    end process;
end Behavioral;

Explanation

• The fix involves explicitly clearing (internal_data <= (others => '0');) the sensitive data when the power_down signal is activated. This ensures that no sensitive information remains in memory during a power-down or debug transition, thus mitigating the vulnerability. By doing so, we prevent potential leakage of sensitive data, ensuring the system remains secure.