Fix GH-21738: undefined behavior in isxdigit() callsites with non-ASCII bytes#21861
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lacatoire wants to merge 2 commits intophp:masterfrom
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Fix GH-21738: undefined behavior in isxdigit() callsites with non-ASCII bytes#21861lacatoire wants to merge 2 commits intophp:masterfrom
lacatoire wants to merge 2 commits intophp:masterfrom
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The isxdigit() family requires its argument to be representable as unsigned char (0-255) or EOF. Casting a signed char value holding a high-bit byte (e.g. 0x80) to int produces a negative number (-128) which triggers undefined behavior, and on some libc implementations (e.g. NetBSD) can lead to out-of-bounds reads through the internal character classification table.
Same signed-char UB as in url_decode: isxdigit() is called on byte values from char-pointers (str_in in quoted_printable_decode, source in php_stripcslashes), which sign-extend to negative int on signed-char platforms when the byte has its high bit set.
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Cast the byte to
unsigned charbefore passing it toisxdigit().<ctype.h>functions require their argument to be representable asunsigned char(0-255) orEOF; passing a sign-extendedcharfor high-bit bytes like\x80is undefined behavior.Callsites fixed:
php_url_decode_exandphp_raw_url_decode_exinext/standard/url.cquoted_printable_decodeinext/standard/quot_print.cphp_stripcslashesinext/standard/string.cFixes GH-21738