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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,201 @@ | ||
| // Licensed to the .NET Foundation under one or more agreements. | ||
| // The .NET Foundation licenses this file to you under the MIT license. | ||
|
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| #include <stdbool.h> | ||
| #include <stdint.h> | ||
| #include "../../Windows/System.IO.Compression.Native/zlib/zutil.h" | ||
|
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| /* A custom allocator for zlib that provides some defense-in-depth over standard malloc / free. | ||
| * (non-Windows version) | ||
| * | ||
| * 1. When zlib allocates fixed-length data structures for containing stream metadata, we zero | ||
| * the memory before using it, preventing use of uninitialized memory within these structures. | ||
| * Ideally we would do this for dynamically-sized buffers as well, but there is a measurable | ||
| * perf impact to doing this. Zeroing fixed structures seems like a good trade-off here, since | ||
| * these data structures contain most of the metadata used for managing the variable-length | ||
| * dynamically allocated buffers. | ||
| * | ||
| * 2. We put a cookie both before and after any allocated memory, which allows us to detect local | ||
| * buffer overruns on the call to free(). The cookie values are tied to the addresses where | ||
| * the data is located in memory. | ||
| * | ||
| * 3. We trash the aforementioned cookie on free(), which allows us to detect double-free. | ||
| * | ||
| * If any of these checks fails, the application raises SIGABRT. | ||
| */ | ||
|
|
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| static bool IsMitigationDisabled() | ||
| { | ||
| enum _MitigationEnablementTristate | ||
| { | ||
| MITIGATION_NOT_YET_QUERIED = 0, | ||
| MITIGATION_DISABLED = 1, | ||
| MITIGATION_ENABLED = 2 // really, anything other than 0 or 1 | ||
| }; | ||
| static int s_fMitigationEnablementState = MITIGATION_NOT_YET_QUERIED; | ||
|
|
||
| // If already initialized, return immediately. | ||
| // We don't need a volatile read here since the publish is performed with release semantics. | ||
| if (s_fMitigationEnablementState != MITIGATION_NOT_YET_QUERIED) | ||
| { | ||
| return (s_fMitigationEnablementState == MITIGATION_DISABLED); | ||
| } | ||
|
|
||
| // Initialize the tri-state now. | ||
| // It's ok for multiple threads to do this simultaneously. Only one thread will win. | ||
| // Valid env var values to disable mitigation: "true" and "1" | ||
| // All other env var values (or error) leaves mitigation enabled. | ||
|
|
||
| char* pchEnvVar = getenv("DOTNET_SYSTEM_IO_COMPRESSION_DISABLEZLIBMITIGATIONS"); | ||
| bool fMitigationDisabled = (pchEnvVar && (strcmp(pchEnvVar, "1") == 0 || strcmp(pchEnvVar, "true") == 0)); | ||
|
|
||
| // We really don't care about the return value of the ICE operation. If another thread | ||
| // beat us to it, so be it. The recursive call will figure it out. | ||
| __sync_val_compare_and_swap( | ||
| /* destination: */ &s_fMitigationEnablementState, | ||
| /* comparand: */ MITIGATION_NOT_YET_QUERIED, | ||
| /* exchange: */ fMitigationDisabled ? MITIGATION_DISABLED : MITIGATION_ENABLED); | ||
| return IsMitigationDisabled(); | ||
| } | ||
|
|
||
| #ifndef MEMORY_ALLOCATION_ALIGNMENT | ||
| // malloc() returns an address suitably aligned for any built-in data type. | ||
| // Historically, this has been twice the arch's natural word size. | ||
| #ifdef HOST_64BIT | ||
| #define MEMORY_ALLOCATION_ALIGNMENT 16 | ||
| #else | ||
| #define MEMORY_ALLOCATION_ALIGNMENT 8 | ||
| #endif | ||
| #endif | ||
|
|
||
| typedef struct _DOTNET_ALLOC_COOKIE | ||
| { | ||
| void* Address; | ||
| size_t Size; | ||
| } DOTNET_ALLOC_COOKIE; | ||
|
|
||
| static bool SafeAdd(size_t a, size_t b, size_t* sum) | ||
| { | ||
| if (SIZE_MAX - a >= b) { *sum = a + b; return true; } | ||
| else { *sum = 0; return false; } | ||
| } | ||
|
|
||
| static bool SafeMult(size_t a, size_t b, size_t* product) | ||
| { | ||
| if (SIZE_MAX / a >= b) { *product = a * b; return true; } | ||
| else { *product = 0; return false; } | ||
| } | ||
|
|
||
| static DOTNET_ALLOC_COOKIE ReadAllocCookieUnaligned(const void* pSrc) | ||
| { | ||
| DOTNET_ALLOC_COOKIE vCookie; | ||
| memcpy(&vCookie, pSrc, sizeof(DOTNET_ALLOC_COOKIE)); | ||
| return vCookie; | ||
| } | ||
|
|
||
| static void WriteAllocCookieUnaligned(void* pDest, DOTNET_ALLOC_COOKIE vCookie) | ||
| { | ||
| memcpy(pDest, &vCookie, sizeof(DOTNET_ALLOC_COOKIE)); | ||
| } | ||
|
|
||
| // Historically, the memory allocator always returns addresses aligned to some | ||
| // particular boundary. We'll make that same guarantee here just in case somebody | ||
| // depends on it. | ||
| const size_t DOTNET_ALLOC_HEADER_COOKIE_SIZE_WITH_PADDING = (sizeof(DOTNET_ALLOC_COOKIE) + MEMORY_ALLOCATION_ALIGNMENT - 1) & ~((size_t)MEMORY_ALLOCATION_ALIGNMENT - 1); | ||
| const size_t DOTNET_ALLOC_TRAILER_COOKIE_SIZE = sizeof(DOTNET_ALLOC_COOKIE); | ||
|
|
||
| voidpf ZLIB_INTERNAL zcalloc(opaque, items, size) | ||
| voidpf opaque; | ||
| unsigned items; | ||
| unsigned size; | ||
| { | ||
| (void)opaque; // unreferenced formal parameter | ||
|
|
||
| if (IsMitigationDisabled()) | ||
| { | ||
| // fallback logic copied from zutil.c | ||
| return sizeof(uInt) > 2 ? (voidpf)malloc(items * size) : | ||
| (voidpf)calloc(items, size); | ||
| } | ||
|
|
||
| // If initializing a fixed-size structure, zero the memory. | ||
| bool fZeroMemory = (items == 1); | ||
|
|
||
| size_t cbRequested; | ||
| if (sizeof(items) + sizeof(size) <= sizeof(cbRequested)) | ||
| { | ||
| // multiplication can't overflow; no need for safeint | ||
| cbRequested = (size_t)items * (size_t)size; | ||
| } | ||
| else | ||
| { | ||
| // multiplication can overflow; go through safeint | ||
| if (!SafeMult((size_t)items, (size_t)size, &cbRequested)) { return NULL; } | ||
| } | ||
|
|
||
| // Make sure the actual allocation has enough room for our frontside & backside cookies. | ||
| size_t cbActualAllocationSize; | ||
| if (!SafeAdd(cbRequested, DOTNET_ALLOC_HEADER_COOKIE_SIZE_WITH_PADDING + DOTNET_ALLOC_TRAILER_COOKIE_SIZE, &cbActualAllocationSize)) { return NULL; } | ||
|
|
||
| void* pAlloced = (fZeroMemory) ? calloc(1, cbActualAllocationSize) : malloc(cbActualAllocationSize); | ||
| if (pAlloced == NULL) { return NULL; } // OOM | ||
|
|
||
| DOTNET_ALLOC_COOKIE* pHeaderCookie = (DOTNET_ALLOC_COOKIE*)pAlloced; | ||
| uint8_t* pReturnToCaller = (uint8_t*)pAlloced + DOTNET_ALLOC_HEADER_COOKIE_SIZE_WITH_PADDING; | ||
| uint8_t* pTrailerCookie = pReturnToCaller + cbRequested; | ||
|
|
||
| // Write out the same cookie for the header & the trailer, then we're done. | ||
|
|
||
| DOTNET_ALLOC_COOKIE vCookie = { 0 }; | ||
| vCookie.Address = pReturnToCaller; | ||
| vCookie.Size = cbRequested; | ||
| *pHeaderCookie = vCookie; // aligned | ||
| WriteAllocCookieUnaligned(pTrailerCookie, vCookie); | ||
|
|
||
| return pReturnToCaller; | ||
| } | ||
|
|
||
| static void zcfree_trash_cookie(void* pCookie) | ||
| { | ||
| memset(pCookie, 0, sizeof(DOTNET_ALLOC_COOKIE)); | ||
| } | ||
|
|
||
| void ZLIB_INTERNAL zcfree(opaque, ptr) | ||
| voidpf opaque; | ||
| voidpf ptr; | ||
| { | ||
| (void)opaque; // unreferenced formal parameter | ||
|
|
||
| if (IsMitigationDisabled()) | ||
| { | ||
| // fallback logic copied from zutil.c | ||
| free(ptr); | ||
| return; | ||
| } | ||
|
|
||
| if (ptr == NULL) { return; } // ok to free nullptr | ||
|
|
||
| // Check cookie at beginning | ||
|
|
||
| DOTNET_ALLOC_COOKIE* pHeaderCookie = (DOTNET_ALLOC_COOKIE*)((uint8_t*)ptr - DOTNET_ALLOC_HEADER_COOKIE_SIZE_WITH_PADDING); | ||
| if (pHeaderCookie->Address != ptr) { goto Fail; } | ||
| size_t cbRequested = pHeaderCookie->Size; | ||
|
|
||
| // Check cookie at end | ||
|
|
||
| uint8_t* pTrailerCookie = (uint8_t*)ptr + cbRequested; | ||
| DOTNET_ALLOC_COOKIE vTrailerCookie = ReadAllocCookieUnaligned(pTrailerCookie); | ||
| if (vTrailerCookie.Address != ptr) { goto Fail; } | ||
| if (vTrailerCookie.Size != cbRequested) { goto Fail; } | ||
|
|
||
| // Checks passed - now trash the cookies and free memory | ||
|
|
||
| zcfree_trash_cookie(pHeaderCookie); | ||
| zcfree_trash_cookie(pTrailerCookie); | ||
|
|
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| free(pHeaderCookie); | ||
| return; | ||
|
|
||
| Fail: | ||
| abort(); // cookie check failed | ||
| } |
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