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string buffer overflow #1222

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merged 2 commits into from
Jan 11, 2017
Merged

string buffer overflow #1222

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dcb03e7
fixes bug in String(const char* str, int len) constructor when the st…
m-mcgowan Dec 29, 2016
638b9b4
API test for String class
sergeuz Jan 11, 2017
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3 changes: 2 additions & 1 deletion wiring/src/spark_wiring_string.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -217,7 +217,8 @@ String & String::copy(const char *cstr, unsigned int length)
return *this;
}
len = length;
strcpy(buffer, cstr);
memcpy(buffer, cstr, length);
buffer[len] = 0;
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Might it not be clearer if it was buffer[len] = '\0';? My C/C++ knowledge is woefully behind y'all's so sorry if the suggestion is silly.

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They are the same thing, but I agree most people see a null terminator and know what's going on without thinking about it. Sometimes the way to go though is to match the style used in the existing file instead of applying your own style here and there. In that light, most of the file uses = 0; and there are only two instances of = '\0';

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The problem isn't null terminating the local buffer, but that it's copying too much data into the buffer. We can't null terminate the cstr at the given length since that's input data (and const).

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Oh, I see what you mean, Using a char instead of an int. Sure we can do that.

return *this;
}

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