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harden filename construction against integer overflow and OOB access #4637

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63 changes: 48 additions & 15 deletions programs/fileio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1195,6 +1195,10 @@ FIO_createFilename_fromOutDir(const char* path, const char* outDirName, const si
const char* filenameStart;
char separator;
char* result;
size_t outDirLen;
size_t filenameLen;
size_t separatorLen;
size_t resultCapacity;

#if defined(_MSC_VER) || defined(__MINGW32__) || defined (__MSVCRT__) /* windows support */
separator = '\\';
Expand All @@ -1207,18 +1211,27 @@ FIO_createFilename_fromOutDir(const char* path, const char* outDirName, const si
filenameStart = extractFilename(filenameStart, '/'); /* sometimes, '/' separator is also used on Windows (mingw+msys2) */
#endif

result = (char*) calloc(1, strlen(outDirName) + 1 + strlen(filenameStart) + suffixLen + 1);
outDirLen = strlen(outDirName);
filenameLen = strlen(filenameStart);
separatorLen = (outDirLen == 0 || outDirName[outDirLen - 1] == separator) ? 0 : 1;

if (outDirLen > (size_t)-1 - separatorLen
|| outDirLen + separatorLen > (size_t)-1 - filenameLen
|| outDirLen + separatorLen + filenameLen > (size_t)-1 - suffixLen - 1) {
EXM_THROW(30, "zstd: FIO_createFilename_fromOutDir: output path too large");
}
resultCapacity = outDirLen + separatorLen + filenameLen + suffixLen + 1;

result = (char*)calloc(1, resultCapacity);
if (!result) {
EXM_THROW(30, "zstd: FIO_createFilename_fromOutDir: %s", strerror(errno));
}

memcpy(result, outDirName, strlen(outDirName));
if (outDirName[strlen(outDirName)-1] == separator) {
memcpy(result + strlen(outDirName), filenameStart, strlen(filenameStart));
} else {
memcpy(result + strlen(outDirName), &separator, 1);
memcpy(result + strlen(outDirName) + 1, filenameStart, strlen(filenameStart));
memcpy(result, outDirName, outDirLen);
if (separatorLen) {
memcpy(result + outDirLen, &separator, 1);
}
memcpy(result + outDirLen + separatorLen, filenameStart, filenameLen);

return result;
}
Expand Down Expand Up @@ -2422,21 +2435,31 @@ FIO_determineCompressedName(const char* srcFileName, const char* outDirName, con
char* outDirFilename = NULL;
size_t sfnSize = strlen(srcFileName);
size_t const srcSuffixLen = strlen(suffix);
size_t requiredCapacity;

if(!strcmp(srcFileName, stdinmark)) {
return stdoutmark;
}

if (outDirName) {
outDirFilename = FIO_createFilename_fromOutDir(srcFileName, outDirName, srcSuffixLen);
sfnSize = strlen(outDirFilename);
assert(outDirFilename != NULL);
sfnSize = strlen(outDirFilename);
}

if (sfnSize > (size_t)-1 - srcSuffixLen - 1) {
EXM_THROW(30, "zstd: destination filename too large");
}
requiredCapacity = sfnSize + srcSuffixLen + 1;

if (dfnbCapacity <= sfnSize+srcSuffixLen+1) {
if (dfnbCapacity <= requiredCapacity) {
/* resize buffer for dstName */
free(dstFileNameBuffer);
dfnbCapacity = sfnSize + srcSuffixLen + 30;
if (requiredCapacity > (size_t)-1 - FNSPACE) {
dfnbCapacity = requiredCapacity;
} else {
dfnbCapacity = requiredCapacity + FNSPACE;
}
dstFileNameBuffer = (char*)malloc(dfnbCapacity);
if (!dstFileNameBuffer) {
EXM_THROW(30, "zstd: %s", strerror(errno));
Expand Down Expand Up @@ -3252,6 +3275,7 @@ FIO_determineDstName(const char* srcFileName, const char* outDirName)
static size_t dfnbCapacity = 0;
static char* dstFileNameBuffer = NULL; /* using static allocation : this function cannot be multi-threaded */
size_t dstFileNameEndPos;
size_t requiredCapacity;
char* outDirFilename = NULL;
const char* dstSuffix = "";
size_t dstSuffixLen = 0;
Expand Down Expand Up @@ -3301,14 +3325,24 @@ FIO_determineDstName(const char* srcFileName, const char* outDirName)

if (outDirName) {
outDirFilename = FIO_createFilename_fromOutDir(srcFileName, outDirName, 0);
sfnSize = strlen(outDirFilename);
assert(outDirFilename != NULL);
sfnSize = strlen(outDirFilename);
}

if (dfnbCapacity+srcSuffixLen <= sfnSize+1+dstSuffixLen) {
dstFileNameEndPos = sfnSize - srcSuffixLen;
if (dstFileNameEndPos > (size_t)-1 - dstSuffixLen - 1) {
EXM_THROW(74, "%s : destination filename too large", strerror(errno));
}
requiredCapacity = dstFileNameEndPos + dstSuffixLen + 1;

if (dfnbCapacity <= requiredCapacity) {
/* allocate enough space to write dstFilename into it */
free(dstFileNameBuffer);
dfnbCapacity = sfnSize + 20;
if (requiredCapacity > (size_t)-1 - FNSPACE) {
dfnbCapacity = requiredCapacity;
} else {
dfnbCapacity = requiredCapacity + FNSPACE;
}
dstFileNameBuffer = (char*)malloc(dfnbCapacity);
if (dstFileNameBuffer==NULL)
EXM_THROW(74, "%s : not enough memory for dstFileName",
Expand All @@ -3317,7 +3351,6 @@ FIO_determineDstName(const char* srcFileName, const char* outDirName)

/* return dst name == src name truncated from suffix */
assert(dstFileNameBuffer != NULL);
dstFileNameEndPos = sfnSize - srcSuffixLen;
if (outDirFilename) {
memcpy(dstFileNameBuffer, outDirFilename, dstFileNameEndPos);
free(outDirFilename);
Expand All @@ -3327,7 +3360,7 @@ FIO_determineDstName(const char* srcFileName, const char* outDirName)

/* The short tar extensions tzst, tgz, txz and tlz4 files should have "tar"
* extension on decompression. Also writes terminating null. */
strcpy(dstFileNameBuffer + dstFileNameEndPos, dstSuffix);
memcpy(dstFileNameBuffer + dstFileNameEndPos, dstSuffix, dstSuffixLen + 1);
return dstFileNameBuffer;

/* note : dstFileNameBuffer memory is not going to be free */
Expand Down