Fix #71848: getimagesize with $imageinfo returns false #3319
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Some JFIF images contain empty APP segments, i.e. those which consist only of the marker bytes and the length, but without actual content. It appears to be doubtful to have empty APP segments, but we should apply the robustness principle, and accept these, instead of simply failing in this case. We choose to add empty APP segments to $imageinfo with an empty string as value, instead of NULL, or even to omit these segments altogether. This patch also fixes the potential issue that php_stream_read() might not read the supposed number of bytes, which could result in garbage to be added to the read value.
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If nobody objects, I'm going to merge this PR during the weekend. |
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Comment on behalf of cmb at php.net: Applied via ae04110 and merged up. |
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Some JFIF images contain empty APP segments, i.e. those which consist
only of the marker bytes and the length, but without actual content.
It appears to be doubtful to have empty APP segments, but we should
apply the robustness principle, and accept these, instead of simply
failing in this case.
We choose to add empty APP segments to $imageinfo with an empty string
as value, instead of NULL, or even to omit these segments altogether.
This patch also fixes the potential issue that php_stream_read() might
not read the supposed number of bytes, which could result in garbage to
be added to the read value.
As far as I know, php_stream_read() returns the actual number of bytes read, and may read less bytes than requested. If so, checking the result for
<= 0would not be correct anyway. Please correct me if I'm wrong.Regarding the decision to add an empty string instead of NULL: this is somewhat arbitrary, given that the meaning of empty APP segments is not clear, but it is the simplest fix, and is certainly not completely illogical.