Replace the popen() call to the external tool sha256sum with OpenSSL's
SHA256 digest algorithm to compute the checksum of a dump image
to improve security of NGDump.
The call to popen() is inherently insecure because a malicious user
controlling a dump device could manipulate the latter and let the user
applying zgetdump to the dump device execute arbitrary shell code.
Furthermore, getting rid of process and shell spawning performed by
popen() shall improve performance of calculation of dump image
checksums.
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
6c6938d1e2