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checking for buffer overflow in insertChars function

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This commit is contained in:
prozessorkern 2021-01-24 20:10:43 +01:00
parent a5bd5c57ab
commit c1f42d8239
2 changed files with 74 additions and 14 deletions
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33
src/shellmatta_utils.c
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@ -162,46 +162,51 @@ void utils_forwardCursor(shellmatta_instance_t *inst, uint32_t length)
* @param[in] inst pointer to shellmatta instance * @param[in] inst pointer to shellmatta instance
* @param[in] data pointer to the data to be inserted * @param[in] data pointer to the data to be inserted
* @param[in] length length of the data to be inserted * @param[in] length length of the data to be inserted
* @todo this function shall check buffer overflows
*/ */
void utils_insertChars( shellmatta_instance_t *inst, void utils_insertChars( shellmatta_instance_t *inst,
char *data, char *data,
uint32_t length) uint32_t length)
{ {
if(0u != length) uint32_t tmpLength = length;
/** -# limit the length to the space left in the buffer */
if((inst->inputCount + tmpLength) > inst->bufferSize)
{ {
tmpLength = inst->bufferSize - inst->inputCount;
}
if(0u != tmpLength)
{
/** -# check if we have to move chars in the buffer */ /** -# check if we have to move chars in the buffer */
if( (inst->cursor != inst->inputCount) if( (inst->cursor != inst->inputCount)
&& (SHELLMATTA_MODE_INSERT == inst->mode)) && (SHELLMATTA_MODE_INSERT == inst->mode))
{ {
/** -# move the existing chars */ /** -# move the existing chars */
for ( uint32_t i = inst->inputCount; for (uint32_t i = inst->inputCount; i > inst->cursor; i --)
i > inst->cursor;
i --)
{ {
inst->buffer[i + length - 1] = inst->buffer[i - 1]; inst->buffer[i + tmpLength - 1] = inst->buffer[i - 1];
} }
/** -# store and print the new chars */ /** -# store and print the new chars */
memcpy(&(inst->buffer[inst->cursor]), data, length); memcpy(&(inst->buffer[inst->cursor]), data, tmpLength);
utils_writeEcho(inst, data, length); utils_writeEcho(inst, data, tmpLength);
/** -# print the other chars and restore the cursor to this position */ /** -# print the other chars and restore the cursor to this position */
utils_eraseLine(inst); utils_eraseLine(inst);
utils_saveCursorPos(inst); utils_saveCursorPos(inst);
utils_writeEcho( inst, utils_writeEcho( inst,
&(inst->buffer[inst->cursor + length]), &(inst->buffer[inst->cursor + tmpLength]),
inst->inputCount - inst->cursor); inst->inputCount - inst->cursor);
utils_restoreCursorPos(inst); utils_restoreCursorPos(inst);
inst->cursor += length; inst->cursor += tmpLength;
inst->inputCount += length; inst->inputCount += tmpLength;
} }
/** -# overwrite - if the cursor reaches the end of the input it is pushed further */ /** -# overwrite - if the cursor reaches the end of the input it is pushed further */
else else
{ {
memcpy(&(inst->buffer[inst->cursor]), data, length); memcpy(&(inst->buffer[inst->cursor]), data, tmpLength);
utils_writeEcho(inst, data, length); utils_writeEcho(inst, data, tmpLength);
inst->cursor += length; inst->cursor += tmpLength;
if(inst->cursor > inst->inputCount) if(inst->cursor > inst->inputCount)
{ {
inst->inputCount = inst->cursor; inst->inputCount = inst->cursor;

55
test/unittest/shellmatta_utils/test_utils_insertChars.cpp
View File

@ -123,3 +123,58 @@ TEST_CASE( "shellmatta_insertChars 0 length" ) {
CHECK( memcmp("\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", write_data, sizeof(write_data) ) == 0u ); CHECK( memcmp("\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", write_data, sizeof(write_data) ) == 0u );
REQUIRE( memcmp("abcdefghij\0\0\0\0\0\0\0\0\0", buffer, sizeof(buffer)) == 0); REQUIRE( memcmp("abcdefghij\0\0\0\0\0\0\0\0\0", buffer, sizeof(buffer)) == 0);
} }
TEST_CASE( "shellmatta_insertChars buffer full" ) {
shellmatta_instance_t inst;
char buffer[20] = "abcdefghij\0\0\0\0\0\0\0\0\0";
memset(&inst, 0, sizeof(inst));
inst.buffer = buffer;
inst.bufferSize = 20;
inst.cursor = 8;
inst.inputCount = 10;
inst.echoEnabled = true;
inst.write = writeFct;
write_callCnt = 0u;
memset(write_data, 0, sizeof(write_data));
write_idx = 0u;
utils_insertChars(&inst, (char*)"blksdflsd kfjlk", 10u);
CHECK( inst.cursor == 18u );
CHECK( inst.inputCount == 20u );
CHECK( write_callCnt == 5u );
CHECK( memcmp("blksdflsd ", write_data, 10u ) == 0u );
REQUIRE( memcmp("abcdefghblksdflsd ij", buffer, sizeof(buffer)) == 0);
}
TEST_CASE( "shellmatta_insertChars buffer overflow by 1" ) {
shellmatta_instance_t inst;
char buffer[20] = "abcdefghij\0\0\0\0\0\0\0\0\0";
memset(&inst, 0, sizeof(inst));
inst.buffer = buffer;
inst.bufferSize = 20;
inst.cursor = 8;
inst.inputCount = 10;
inst.echoEnabled = true;
inst.write = writeFct;
write_callCnt = 0u;
memset(write_data, 0, sizeof(write_data));
write_idx = 0u;
utils_insertChars(&inst, (char*)"blksdflsd kfjlk", 11u);
CHECK( inst.cursor == 18u );
CHECK( inst.inputCount == 20u );
CHECK( write_callCnt == 5u );
CHECK( memcmp("blksdflsd ", write_data, 10u ) == 0u );
REQUIRE( memcmp("abcdefghblksdflsd ij", buffer, sizeof(buffer)) == 0);
}