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63 lines
1.5 KiB
C
63 lines
1.5 KiB
C
// Use `getentropy` from unistd.h //////////////////////////////////////////////
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#if defined(ENT_GETENTROPY_UNISTD)
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#include <stddef.h>
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#include <unistd.h>
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int ent_getentropy(void* buf, size_t len) {
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return getentropy(buf, len);
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}
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// Use `getentropy` from sys/random.h //////////////////////////////////////////
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#elif defined(ENT_GETENTROPY_SYSRANDOM)
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#include <stddef.h>
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#include <sys/random.h>
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int ent_getentropy(void* buf, size_t len) {
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return getentropy(buf, len);
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}
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// Use the `getrandom` syscall /////////////////////////////////////////////////
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#elif defined(ENT_GETRANDOM_SYSCALL)
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#include <stddef.h>
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#include <errno.h>
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#define _GNU_SOURCE
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#include <unistd.h>
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#include <sys/syscall.h>
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#define ENTFAIL { errno=EIO; return -1; }
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int ent_getentropy(void* buf, size_t len) {
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if (len > 256) ENTFAIL
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int r = syscall(SYS_getrandom, buf, len, 0);
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if (r < 0) return r;
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if (r != len) ENTFAIL
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return 0;
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}
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// Use `/dev/urandom` //////////////////////////////////////////////////////////
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#elif defined(ENT_DEV_URANDOM)
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#include <stddef.h>
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#include <errno.h>
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#include <stdio.h>
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#define ENTFAIL { errno=EIO; return -1; }
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int ent_getentropy(void* buf, size_t len) {
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if (len > 256) ENTFAIL;
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FILE *f = fopen("/dev/urandom", "re");
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if (!f) return -1;
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int r = fread(buf, 1, len, f);
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(void) fclose(f);
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if (r != len) ENTFAIL
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return 0;
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}
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#else
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#error "One of these must be set: ENT_DEV_URANDOM, ENT_GETENTROPY_UNISTD, ENT_GETENTROPY_SYSRANDOM, ENT_GETRANDOM_SYSCALL"
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#endif
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