From a54611f16cf2140d93f8a33563bbc79af136636a Mon Sep 17 00:00:00 2001
From: Kristian Evers <kristianevers@gmail.com>
Date: Tue, 23 May 2017 17:37:42 +0200
Subject: Fix possible zero division.

For some extreme values of eccentricity a zero divison can occur. In
those rare cases we return HUGE_VAL to indicate something went wrong
while still returning a defined value.

Credit to OSS Fuzz.

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=1801
---
 src/pj_tsfn.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

(limited to 'src')

diff --git a/src/pj_tsfn.c b/src/pj_tsfn.c
index 448aae99..eff20cab 100644
--- a/src/pj_tsfn.c
+++ b/src/pj_tsfn.c
@@ -2,9 +2,15 @@
 #include <math.h>
 #include <projects.h>
 
-	double
-pj_tsfn(double phi, double sinphi, double e) {
-	sinphi *= e;
-	return (tan (.5 * (M_HALFPI - phi)) /
-	   pow((1. - sinphi) / (1. + sinphi), .5 * e));
+double pj_tsfn(double phi, double sinphi, double e) {
+    double denominator;
+    sinphi *= e;
+
+    /* avoid zero division, fail gracefully */
+    denominator = 1.0 + sinphi;
+    if (denominator == 0.0)
+        return HUGE_VAL;
+
+    return (tan (.5 * (M_HALFPI - phi)) /
+            pow((1. - sinphi) / (denominator), .5 * e));
 }
-- 
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