diff options
| -rw-r--r-- | src/backend/postmaster/postmaster.c | 33 | ||||
| -rw-r--r-- | src/port/pg_strong_random.c | 12 |
2 files changed, 31 insertions, 14 deletions
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c index eedc617db4c..2d5a0ac7d3b 100644 --- a/src/backend/postmaster/postmaster.c +++ b/src/backend/postmaster/postmaster.c @@ -2520,11 +2520,13 @@ ClosePostmasterPorts(bool am_syslogger) /* * InitProcessGlobals -- set MyProcPid, MyStartTime[stamp], random seeds * - * Called early in every backend. + * Called early in the postmaster and every backend. */ void InitProcessGlobals(void) { + unsigned int rseed; + MyProcPid = getpid(); MyStartTimestamp = GetCurrentTimestamp(); MyStartTime = timestamptz_to_time_t(MyStartTimestamp); @@ -2539,15 +2541,30 @@ InitProcessGlobals(void) #endif /* - * Set a different seed for random() in every backend. Since PIDs and - * timestamps tend to change more frequently in their least significant - * bits, shift the timestamp left to allow a larger total number of seeds - * in a given time period. Since that would leave only 20 bits of the - * timestamp that cycle every ~1 second, also mix in some higher bits. + * Set a different seed for random() in every process. We want something + * unpredictable, so if possible, use high-quality random bits for the + * seed. Otherwise, fall back to a seed based on timestamp and PID. + * + * Note we can't use pg_backend_random here, since this is used in the + * postmaster, and even in a backend we might not be attached to shared + * memory yet. */ - srandom(((uint64) MyProcPid) ^ +#ifdef HAVE_STRONG_RANDOM + if (!pg_strong_random(&rseed, sizeof(rseed))) +#endif + { + /* + * Since PIDs and timestamps tend to change more frequently in their + * least significant bits, shift the timestamp left to allow a larger + * total number of seeds in a given time period. Since that would + * leave only 20 bits of the timestamp that cycle every ~1 second, + * also mix in some higher bits. + */ + rseed = ((uint64) MyProcPid) ^ ((uint64) MyStartTimestamp << 12) ^ - ((uint64) MyStartTimestamp >> 20)); + ((uint64) MyStartTimestamp >> 20); + } + srandom(rseed); } diff --git a/src/port/pg_strong_random.c b/src/port/pg_strong_random.c index f9a06d66061..1408d3ad88e 100644 --- a/src/port/pg_strong_random.c +++ b/src/port/pg_strong_random.c @@ -6,6 +6,10 @@ * Our definition of "strong" is that it's suitable for generating random * salts and query cancellation keys, during authentication. * + * Note: this code is run quite early in postmaster and backend startup; + * therefore, even when built for backend, it cannot rely on backend + * infrastructure such as elog() or palloc(). + * * Copyright (c) 1996-2018, PostgreSQL Global Development Group * * IDENTIFICATION @@ -14,11 +18,7 @@ *------------------------------------------------------------------------- */ -#ifndef FRONTEND -#include "postgres.h" -#else -#include "postgres_fe.h" -#endif +#include "c.h" #include <fcntl.h> #include <unistd.h> @@ -44,7 +44,7 @@ static HCRYPTPROV hProvider = 0; * Read (random) bytes from a file. */ static bool -random_from_file(char *filename, void *buf, size_t len) +random_from_file(const char *filename, void *buf, size_t len) { int f; char *p = buf; |