Fragmented FBX ASCII emdedded resource

code/FBXDocument.h

@@ -643,7 +643,7 @@ private:
     std::string fileName;
     std::shared_ptr<const PropertyTable> props;
 
-    uint32_t contentLength;
+    uint64_t contentLength;
     uint8_t* content;
 };
 

code/FBXMaterial.cpp

@@ -326,16 +326,40 @@ Video::Video(uint64_t id, const Element& element, const Document& doc, const std
                     DOMError("embedded content is not surrounded by quotation marks", &element);
                 }
                 else {
-                    const char* encodedData = data + 1;
+                    size_t targetLength = 0;
-                    size_t encodedDataLen = static_cast<size_t>(token.end() - token.begin());
+                    auto numTokens = Content->Tokens().size();
-                    // search for last quotation mark
+                    // First time compute size (it could be large like 64Gb and it is good to allocate it once)
-                    while (encodedDataLen > 1 && encodedData[encodedDataLen] != '"')
+                    for (uint32_t tokenIdx = 0; tokenIdx < numTokens; ++tokenIdx)
-                        encodedDataLen--;
+                    {
-                    if (encodedDataLen % 4 != 0) {
+                        const Token& dataToken = GetRequiredToken(*Content, tokenIdx);
-                        DOMError("embedded content is invalid, needs to be in base64", &element);
+                        size_t tokenLength = dataToken.end() - dataToken.begin() - 2; // ignore double quotes
+                        const char* base64data = dataToken.begin() + 1;
+                        const size_t outLength = Util::ComputeDecodedSizeBase64(base64data, tokenLength);
+                        if (outLength == 0)
+                        {
+                            DOMError("Corrupted embedded content found", &element);
+                        }
+                        targetLength += outLength;
                     }
-                    else {
+                    if (targetLength == 0)
-                        contentLength = Util::DecodeBase64(encodedData, encodedDataLen, content);
+                    {
+                        DOMError("Corrupted embedded content found", &element);
+                    }
+                    content = new uint8_t[targetLength];
+                    contentLength = static_cast<uint64_t>(targetLength);
+                    size_t dst_offset = 0;
+                    for (uint32_t tokenIdx = 0; tokenIdx < numTokens; ++tokenIdx)
+                    {
+                        const Token& dataToken = GetRequiredToken(*Content, tokenIdx);
+                        size_t tokenLength = dataToken.end() - dataToken.begin() - 2; // ignore double quotes
+                        const char* base64data = dataToken.begin() + 1;
+                        dst_offset += Util::DecodeBase64(base64data, tokenLength, content + dst_offset, targetLength - dst_offset);
+                    }
+                    if (targetLength != dst_offset)
+                    {
+                        delete[] content;
+                        contentLength = 0;
+                        DOMError("Corrupted embedded content found", &element);
                     }
                 }
             }

code/FBXUtil.cpp

@@ -114,47 +114,65 @@ std::string AddTokenText(const std::string& prefix, const std::string& text, con
         text) );
 }
 
+// Generated by this formula: T["ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"[i]] = i;
 static const uint8_t base64DecodeTable[128] = {
-    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0, 62,  0,  0,  0, 63,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63,
-    52, 53, 54, 55, 56, 57, 58, 59, 60, 61,  0,  0,  0, 64,  0,  0,
+    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 255, 255, 255, 255,
-    0,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+    255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
-    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,  0,  0,  0,  0,  0,
+    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255,
-    0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+    255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
-    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,  0,  0,  0,  0,  0
+    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 255, 255, 255, 255, 255
 };
 
 uint8_t DecodeBase64(char ch)
 {
-    return base64DecodeTable[size_t(ch)];
+    const auto idx = static_cast<uint8_t>(ch);
+    if (idx > 127)
+        return 255;
+    return base64DecodeTable[idx];
 }
 
-size_t DecodeBase64(const char* in, size_t inLength, uint8_t*& out)
+size_t ComputeDecodedSizeBase64(const char* in, size_t inLength)
 {
-    if (inLength < 4) {
+    if (inLength < 2)
-        out = 0;
+    {
         return 0;
     }
-
+    const size_t equals = size_t(in[inLength - 1] == '=') + size_t(in[inLength - 2] == '=');
-    const size_t outLength = (inLength * 3) / 4;
+    const size_t full_length = (inLength * 3) >> 2; // div by 4
-    out = new uint8_t[outLength];
+    if (full_length < equals)
-    memset(out, 0, outLength);
-
-    size_t i = 0;
-    size_t j = 0;
-    for (i = 0; i < inLength - 4; i += 4)
     {
-        uint8_t b0 = Util::DecodeBase64(in[i]);
+        return 0;
-        uint8_t b1 = Util::DecodeBase64(in[i + 1]);
-        uint8_t b2 = Util::DecodeBase64(in[i + 2]);
-        uint8_t b3 = Util::DecodeBase64(in[i + 3]);
-
-        out[j++] = (uint8_t)((b0 << 2) | (b1 >> 4));
-        out[j++] = (uint8_t)((b1 << 4) | (b2 >> 2));
-        out[j++] = (uint8_t)((b2 << 6) | b3);
     }
-    return outLength;
+    return full_length - equals;
+}
+
+size_t DecodeBase64(const char* in, size_t inLength, uint8_t* out, size_t maxOutLength)
+{
+    if (maxOutLength == 0 || inLength < 2) {
+        return 0;
+    }
+    const size_t realLength = inLength - size_t(in[inLength - 1] == '=') - size_t(in[inLength - 2] == '=');
+    size_t dst_offset = 0;
+    int val = 0, valb = -8;
+    for (size_t src_offset = 0; src_offset < realLength; ++src_offset)
+    {
+        const uint8_t table_value = Util::DecodeBase64(in[src_offset]);
+        if (table_value == 255)
+        {
+            return 0;
+        }
+        val = (val << 6) + table_value;
+        valb += 6;
+        if (valb >= 0)
+        {
+            out[dst_offset++] = static_cast<uint8_t>((val >> valb) & 0xFF);
+            valb -= 8;
+        }
+    }
+    return dst_offset;
 }
 
 static const char to_base64_string[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

code/FBXUtil.h

@@ -105,13 +105,21 @@ std::string AddTokenText(const std::string& prefix, const std::string& text, con
 *  @return decoded byte value*/
 uint8_t DecodeBase64(char ch);
 
+/** Compute decoded size of a Base64-encoded string
+*
+*  @param in Characters to decode.
+*  @param inLength Number of characters to decode.
+*  @return size of the decoded data (number of bytes)*/
+size_t ComputeDecodedSizeBase64(const char* in, size_t inLength);
+
 /** Decode a Base64-encoded string
 *
 *  @param in Characters to decode.
 *  @param inLength Number of characters to decode.
-*  @param out Reference to pointer where we will store the decoded data.
+*  @param out Pointer where we will store the decoded data.
+*  @param maxOutLength Size of output buffer.
 *  @return size of the decoded data (number of bytes)*/
-size_t DecodeBase64(const char* in, size_t inLength, uint8_t*& out);
+size_t DecodeBase64(const char* in, size_t inLength, uint8_t* out, size_t maxOutLength);
 
 char EncodeBase64(char byte);
 

test/unit/utFBXImporterExporter.cpp

@@ -128,4 +128,28 @@ TEST_F(utFBXImporterExporter, importEmbeddedAsciiTest) {
     aiString path;
     aiTextureMapMode modes[2];
     EXPECT_EQ(aiReturn_SUCCESS, mat->GetTexture(aiTextureType_DIFFUSE, 0, &path, nullptr, nullptr, nullptr, nullptr, modes));
+
+    ASSERT_EQ(1, scene->mNumTextures);
+    ASSERT_TRUE(scene->mTextures[0]->pcData);
+    ASSERT_EQ(439176u, scene->mTextures[0]->mWidth) << "FBX ASCII base64 compression splits data by 512Kb, it should be two parts for this texture";
+}
+
+TEST_F(utFBXImporterExporter, importEmbeddedFragmentedAsciiTest) {
+    // see https://github.com/assimp/assimp/issues/1957
+    Assimp::Importer importer;
+    const aiScene *scene = importer.ReadFile(ASSIMP_TEST_MODELS_DIR "/FBX/embedded_ascii/box_embedded_texture_fragmented.fbx", aiProcess_ValidateDataStructure);
+    EXPECT_NE(nullptr, scene);
+
+    EXPECT_EQ(1, scene->mNumMaterials);
+    aiMaterial *mat = scene->mMaterials[0];
+    ASSERT_NE(nullptr, mat);
+
+    aiString path;
+    aiTextureMapMode modes[2];
+    ASSERT_EQ(aiReturn_SUCCESS, mat->GetTexture(aiTextureType_DIFFUSE, 0, &path, nullptr, nullptr, nullptr, nullptr, modes));
+    ASSERT_STREQ(path.C_Str(), "paper.png");
+
+    ASSERT_EQ(1, scene->mNumTextures);
+    ASSERT_TRUE(scene->mTextures[0]->pcData);
+    ASSERT_EQ(968029u, scene->mTextures[0]->mWidth) << "FBX ASCII base64 compression splits data by 512Kb, it should be two parts for this texture";
 }