Perform ParityEven7bit, ParityOdd7bit & ParityZero7bit transformations in-place

- Refactored to share implementations of ParityEven7bit & ParityOdd7bit.

Author: eduar-hte

src/actions/transformations/parity_even_7bit.cc

@@ -15,53 +15,12 @@
 
 #include "parity_even_7bit.h"
 
-#include <cstring>
-
 
 namespace modsecurity::actions::transformations {
 
 
 bool ParityEven7bit::transform(std::string &value, const Transaction *trans) const {
-    if (value.empty()) return false;
-
-    unsigned char *input;
-
-    input = reinterpret_cast<unsigned char *>
-        (malloc(sizeof(char) * value.length()+1));
-
-    if (input == NULL) {
-        return "";
-    }
-
-    std::memcpy(input, value.c_str(), value.length()+1);
-
-    const auto ret = inplace(input, value.length());
-
-    value.assign(reinterpret_cast<char *>(input), value.length());
-    free(input);
-
-    return ret;
-}
-
-bool ParityEven7bit::inplace(unsigned char *input, uint64_t input_len) {
-    uint64_t i;
-
-    i = 0;
-    while (i < input_len) {
-        unsigned int x = input[i];
-
-        input[i] ^= input[i] >> 4;
-        input[i] &= 0xf;
-
-        if ((0x6996 >> input[i]) & 1) {
-            input[i] = x | 0x80;
-        } else {
-            input[i] = x & 0x7f;
-        }
-        i++;
-    }
-
-    return true;
+    return ParityEven7bit::inplace<true>(value);
 }
 
 

src/actions/transformations/parity_even_7bit.h

@@ -26,7 +26,28 @@ class ParityEven7bit : public Transformation {
         : Transformation(action) { }
 
     bool transform(std::string &value, const Transaction *trans) const override;
-    static bool inplace(unsigned char *input, uint64_t input_len);
+
+    template<bool even>
+    static bool inplace(std::string &value) {
+        if (value.empty()) return false;
+
+        for(auto &c : value) {
+            auto &uc = reinterpret_cast<unsigned char&>(c);
+            unsigned int x = uc;
+
+            uc ^= uc >> 4;
+            uc &= 0xf;
+
+            const bool condition = (0x6996 >> uc) & 1;
+            if (even ? condition : !condition) {
+                uc = x | 0x80;
+            } else {
+                uc = x & 0x7f;
+            }
+        }
+
+        return true;
+    }
 };
 
 }  // namespace modsecurity::actions::transformations

src/actions/transformations/parity_odd_7bit.cc

@@ -14,54 +14,14 @@
  */
 
 #include "parity_odd_7bit.h"
-
-#include <cstring>
+#include "parity_even_7bit.h"
 
 
 namespace modsecurity::actions::transformations {
 
 
 bool ParityOdd7bit::transform(std::string &value, const Transaction *trans) const {
-    if (value.empty()) return false;
-
-    unsigned char *input;
-
-    input = reinterpret_cast<unsigned char *>
-        (malloc(sizeof(char) * value.length()+1));
-
-    if (input == NULL) {
-        return "";
-    }
-
-    memcpy(input, value.c_str(), value.length()+1);
-
-    const auto ret = inplace(input, value.length());
-
-    value.assign(reinterpret_cast<char *>(input), value.length());
-    free(input);
-
-    return ret;
-}
-
-bool ParityOdd7bit::inplace(unsigned char *input, uint64_t input_len) {
-    uint64_t i;
-
-    i = 0;
-    while (i < input_len) {
-        unsigned int x = input[i];
-
-        input[i] ^= input[i] >> 4;
-        input[i] &= 0xf;
-
-        if ((0x6996 >> input[i]) & 1) {
-            input[i] = x & 0x7f;
-        } else {
-            input[i] = x | 0x80;
-        }
-        i++;
-    }
-
-    return true;
+    return ParityEven7bit::inplace<false>(value);
 }
 
 

src/actions/transformations/parity_odd_7bit.h

@@ -26,7 +26,6 @@ class ParityOdd7bit : public Transformation {
         : Transformation(action) { }
 
     bool transform(std::string &value, const Transaction *trans) const override;
-    static bool inplace(unsigned char *input, uint64_t input_len);
 };
 
 }  // namespace modsecurity::actions::transformations

src/actions/transformations/parity_zero_7bit.cc

@@ -15,45 +15,23 @@
 
 #include "parity_zero_7bit.h"
 
-#include <cstring>
-
 
 namespace modsecurity::actions::transformations {
 
 
-bool ParityZero7bit::transform(std::string &value, const Transaction *trans) const {
+static inline bool inplace(std::string &value) {
     if (value.empty()) return false;
 
-    unsigned char *input;
-
-    input = reinterpret_cast<unsigned char *>
-        (malloc(sizeof(char) * value.length()+1));
-
-    if (input == NULL) {
-        return "";
+    for(auto &c : value) {
+        ((unsigned char&)c) &= 0x7f;
     }
 
-    memcpy(input, value.c_str(), value.length()+1);
-
-    const auto ret = inplace(input, value.length());
-
-    value.assign(reinterpret_cast<char *>(input), value.length());
-    free(input);
-
-    return ret;
+    return true;
 }
 
 
-bool ParityZero7bit::inplace(unsigned char *input, uint64_t input_len) {
-    uint64_t i;
-
-    i = 0;
-    while (i < input_len) {
-        input[i] &= 0x7f;
-        i++;
-    }
-
-    return true;
+bool ParityZero7bit::transform(std::string &value, const Transaction *trans) const {
+    return inplace(value);
 }
 
 

src/actions/transformations/parity_zero_7bit.h

@@ -26,7 +26,6 @@ class ParityZero7bit : public Transformation {
         : Transformation(action) { }
 
     bool transform(std::string &value, const Transaction *trans) const override;
-    static bool inplace(unsigned char *input, uint64_t input_len);
 };
 
 }  // namespace modsecurity::actions::transformations