1 /* Copyright libuv contributors. All rights reserved. 2 * 3 * Permission is hereby granted, free of charge, to any person obtaining a copy 4 * of this software and associated documentation files (the "Software"), to 5 * deal in the Software without restriction, including without limitation the 6 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or 7 * sell copies of the Software, and to permit persons to whom the Software is 8 * furnished to do so, subject to the following conditions: 9 * 10 * The above copyright notice and this permission notice shall be included in 11 * all copies or substantial portions of the Software. 12 * 13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 16 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 18 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 19 * IN THE SOFTWARE. 20 */ 21 22 #include "uv.h" 23 #include "internal.h" 24 25 #include <errno.h> 26 #include <string.h> 27 28 #include <syscall.h> 29 #include <unistd.h> 30 31 32 struct uv__sysctl_args { 33 int* name; 34 int nlen; 35 void* oldval; 36 size_t* oldlenp; 37 void* newval; 38 size_t newlen; 39 unsigned long unused[4]; 40 }; 41 42 43 int uv__random_sysctl(void* buf, size_t buflen) { 44 static int name[] = {1 /*CTL_KERN*/, 40 /*KERN_RANDOM*/, 6 /*RANDOM_UUID*/}; 45 struct uv__sysctl_args args; 46 char uuid[16]; 47 char* p; 48 char* pe; 49 size_t n; 50 51 p = buf; 52 pe = p + buflen; 53 54 while (p < pe) { 55 memset(&args, 0, sizeof(args)); 56 57 args.name = name; 58 args.nlen = ARRAY_SIZE(name); 59 args.oldval = uuid; 60 args.oldlenp = &n; 61 n = sizeof(uuid); 62 63 /* Emits a deprecation warning with some kernels but that seems like 64 * an okay trade-off for the fallback of the fallback: this function is 65 * only called when neither getrandom(2) nor /dev/urandom are available. 66 * Fails with ENOSYS on kernels configured without CONFIG_SYSCTL_SYSCALL. 67 * At least arm64 never had a _sysctl system call and therefore doesn't 68 * have a SYS__sysctl define either. 69 */ 70 #ifdef SYS__sysctl 71 if (syscall(SYS__sysctl, &args) == -1) 72 return UV__ERR(errno); 73 #else 74 { 75 (void) &args; 76 return UV_ENOSYS; 77 } 78 #endif 79 80 if (n != sizeof(uuid)) 81 return UV_EIO; /* Can't happen. */ 82 83 /* uuid[] is now a type 4 UUID. Bytes 6 and 8 (counting from zero) contain 84 * 4 and 5 bits of entropy, respectively. For ease of use, we skip those 85 * and only use 14 of the 16 bytes. 86 */ 87 uuid[6] = uuid[14]; 88 uuid[8] = uuid[15]; 89 90 n = pe - p; 91 if (n > 14) 92 n = 14; 93 94 memcpy(p, uuid, n); 95 p += n; 96 } 97 98 return 0; 99 } 100