sha256: fix undefined behavior in left shift of BYTE by 24#40
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MayCXC wants to merge 1 commit intoB-Con:masterfrom
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sha256: fix undefined behavior in left shift of BYTE by 24#40MayCXC wants to merge 1 commit intoB-Con:masterfrom
MayCXC wants to merge 1 commit intoB-Con:masterfrom
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In sha256_transform, the expression `data[j] << 24` promotes the BYTE (unsigned char) operand to int (signed 32-bit) before shifting. When data[j] >= 128, shifting by 24 produces a value that cannot be represented in a signed 32-bit int, which is undefined behavior per the C standard. Found by UndefinedBehaviorSanitizer: sha256.c:49:19: runtime error: left shift of 128 by 24 places cannot be represented in type 'int' Fix: explicitly cast each BYTE to WORD (unsigned int) before shifting. This ensures the shift operates on unsigned 32-bit values throughout.
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In
sha256_transform, the expressiondata[j] << 24promotes theBYTE(unsigned char) operand toint(signed 32-bit) before shifting. Whendata[j] >= 128, shifting by 24 produces a value that cannot be represented in a signed 32-bit int, which is undefined behavior per the C standard (C11 6.5.7p4).Found by UndefinedBehaviorSanitizer:
Fix: cast each
BYTEtoWORD(unsigned int) before shifting. This ensures the shift operates on unsigned 32-bit values, which is well-defined for all byte values.The fix is a single line change with no behavioral difference for correct inputs (the UB happened to produce the correct result on all common platforms, but relying on UB is not portable).