ref: 72a8af8a0d1405295f0901d30bee3b95ff239dd2
dir: /sys/src/cmd/auth/rsa2any.h/
RSApriv*getrsakey(int argc, char **argv, int needprivate, Attr **pa); uchar* put4(uchar *p, uint n); uchar* putmp2(uchar *p, mpint *b); uchar* putn(uchar *p, void *v, uint n); uchar* putstr(uchar *p, char *s);