From 4e75b40d8a96c5d51490ddea43566fe8e6d4168c Mon Sep 17 00:00:00 2001
From: Laurent Bercot <ska-skaware@skarnet.org>
Date: Sat, 9 Apr 2022 02:28:05 +0000
Subject:  Prepare for 2.12.0.0. librandom revamp.

Signed-off-by: Laurent Bercot <ska@appnovation.com>
---
 src/librandom/autosurf.c | 48 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 3 deletions(-)

(limited to 'src/librandom/autosurf.c')

diff --git a/src/librandom/autosurf.c b/src/librandom/autosurf.c
index 04a47c2..0a219b8 100644
--- a/src/librandom/autosurf.c
+++ b/src/librandom/autosurf.c
@@ -1,17 +1,59 @@
 /* ISC license. */
 
+#include <unistd.h>
+#include <stdint.h>
+
+#include <skalibs/uint32.h>
+#include <skalibs/tai.h>
+#include <skalibs/sha1.h>
 #include <skalibs/random.h>
 #include <skalibs/surf.h>
 
+/*
+   Writes 160 bytes of crap into s.
+   Certainly not cryptographically secure or 100% unpredictable,
+   but we're only using this to seed a fallback internal PRNG.
+*/
+
+static void makeseed (char *s)
+{
+  SHA1Schedule bak = SHA1_INIT() ;
+  {
+    tain now ;
+    char tmp[256] ;
+    uint32_t x = getpid() ;
+    uint32_pack(tmp, x) ;  /* if valgrind sends you here, tell it to stfu */
+    x = getppid() ;
+    uint32_pack(tmp + 4, x) ;
+    tain_now(&now) ;
+    tain_pack(tmp + 8, &now) ;
+    sha1_update(&bak, tmp, 8 + TAIN_PACK) ;
+    gethostname(tmp, 256) ;
+    sha1_update(&bak, tmp, 256) ;
+    sha1_final(&bak, tmp) ;
+    sha1_init(&bak) ;
+    sha1_update(&bak, tmp, 20) ;
+  }
+  {
+    char i = 0 ;
+    for (; i < 8 ; i++)
+    {
+      SHA1Schedule ctx = bak ;
+      sha1_update(&ctx, &i, 1) ;
+      sha1_final(&ctx, s + 20*i) ;
+    }
+  }
+}
+
 void autosurf (char *s, size_t n)
 {
   static SURFSchedule ctx = SURFSCHEDULE_ZERO ;
   static int need4seed = 1 ;
   if (need4seed)
   {
-    char tmp[160] ;
-    random_makeseed(tmp) ;
-    surf_init(&ctx, tmp) ;
+    char seed[160] ;
+    makeseed(seed) ;
+    surf_init(&ctx, seed) ;
     need4seed = 0 ;
   }
   surf(&ctx, s, n) ;
-- 
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