Merge pull request ReFirmLabs#782 from ReFirmLabs/uboot_version

Added U-Boot version signature, fixed openssl signature validation

src/common.rs

@@ -119,6 +119,40 @@ pub fn get_cstring(raw_data: &[u8]) -> String {
     string
 }
 
+/// Returns true if the provided byte is an ASCII number
+///
+/// ## Example
+///
+/// ```
+/// use binwalk::common::is_ascii_number;
+///
+/// assert!(is_ascii_number(0x31));
+/// assert!(!is_ascii_number(0xFE));
+/// ```
+pub fn is_ascii_number(b: u8) -> bool {
+    const ZERO: u8 = 48;
+    const NINE: u8 = 57;
+
+    (ZERO..=NINE).contains(&b)
+}
+
+/// Returns true if the provided byte is a printable ASCII character
+///
+/// ## Example
+///
+/// ```
+/// use binwalk::common::is_printable_ascii;
+///
+/// assert!(is_printable_ascii(0x41));
+/// assert!(!is_printable_ascii(0xFE));
+/// ```
+pub fn is_printable_ascii(b: u8) -> bool {
+    const ASCII_MIN: u8 = 0x0A;
+    const ASCII_MAX: u8 = 0x7E;
+
+    (ASCII_MIN..=ASCII_MAX).contains(&b)
+}
+
 /// Validates data offsets to prevent out-of-bounds access and infinite loops while parsing file formats.
 ///
 /// ## Notes

src/magic.rs

@@ -1075,6 +1075,17 @@ pub fn patterns() -> Vec<signatures::common::Signature> {
             description: signatures::android_bootimg::DESCRIPTION.to_string(),
             extractor: None,
         },
+        // uboot
+        signatures::common::Signature {
+            name: "uboot".to_string(),
+            short: false,
+            magic_offset: 0,
+            always_display: true,
+            magic: signatures::uboot::uboot_magic(),
+            parser: signatures::uboot::uboot_parser,
+            description: signatures::uboot::DESCRIPTION.to_string(),
+            extractor: None,
+        },
     ];
 
     binary_signatures

src/signatures.rs

@@ -181,6 +181,7 @@ pub mod tarball;
 pub mod tplink;
 pub mod trx;
 pub mod ubi;
+pub mod uboot;
 pub mod uefi;
 pub mod uimage;
 pub mod vxworks;

src/signatures/openssl.rs

@@ -1,3 +1,4 @@
+use crate::common::is_printable_ascii;
 use crate::signatures::common::{
     SignatureError, SignatureResult, CONFIDENCE_LOW, CONFIDENCE_MEDIUM,
 };
@@ -24,13 +25,10 @@ pub fn openssl_crypt_parser(
         ..Default::default()
     };
 
-    // This "salt" value are the bytes commonly found in the openssl binary itself
-    let known_false_positive_salts: Vec<usize> = vec![0x2D252D32];
-
     // Parse the header
     if let Ok(openssl_header) = parse_openssl_crypt_header(&file_data[offset..]) {
-        // Check common false positive salt values
-        if !known_false_positive_salts.contains(&openssl_header.salt) {
+        // Sanity check the salt value
+        if !is_salt_invalid(openssl_header.salt) {
             // If the magic starts at the beginning of a file, our confidence is a bit higher
             if offset == 0 {
                 result.confidence = CONFIDENCE_MEDIUM;
@@ -44,3 +42,20 @@ pub fn openssl_crypt_parser(
 
     Err(SignatureError)
 }
+
+// Returns true if the salt is entirely comprised of NULL and/or ASCII bytes
+fn is_salt_invalid(salt: usize) -> bool {
+    const SALT_LEN: usize = 8;
+
+    let mut bad_byte_count: usize = 0;
+
+    for i in 0..SALT_LEN {
+        let salt_byte = ((salt >> (8 * i)) & 0xFF) as u8;
+
+        if salt_byte == 0 || is_printable_ascii(salt_byte) {
+            bad_byte_count += 1;
+        }
+    }
+
+    bad_byte_count == SALT_LEN
+}

src/signatures/uboot.rs

@@ -0,0 +1,37 @@
+use crate::common::{get_cstring, is_ascii_number};
+use crate::signatures::common::{SignatureError, SignatureResult, CONFIDENCE_MEDIUM};
+
+/// Human readable description
+pub const DESCRIPTION: &str = "U-Boot version string";
+
+/// U-Boot version number magic bytes
+pub fn uboot_magic() -> Vec<Vec<u8>> {
+    vec![b"U-Boot\x20".to_vec()]
+}
+
+/// Validates the U-Boot version number magic
+pub fn uboot_parser(file_data: &[u8], offset: usize) -> Result<SignatureResult, SignatureError> {
+    const NUMBER_OFFSET: usize = 7;
+
+    // Successful return value
+    let mut result = SignatureResult {
+        offset,
+        description: DESCRIPTION.to_string(),
+        confidence: CONFIDENCE_MEDIUM,
+        ..Default::default()
+    };
+
+    if let Some(expected_number_byte) = file_data.get(offset + NUMBER_OFFSET) {
+        if is_ascii_number(*expected_number_byte) {
+            let uboot_version_string = get_cstring(&file_data[offset + NUMBER_OFFSET..]);
+
+            if !uboot_version_string.is_empty() {
+                result.size = uboot_version_string.len();
+                result.description = format!("{}: {}", result.description, uboot_version_string);
+                return Ok(result);
+            }
+        }
+    }
+
+    Err(SignatureError)
+}