bn256: fix String methods when g.p == nil
Previously, when g.p == nil, String() crashed. In other method like Add(),
a point with g.p == nil is treated as an identity element.
Besides, the following code is the only way to get an identity element
outside the library: g := bn256.G1{}. In this situation, g.p == nil.
For example, the following code will crash:
package main
import (
"fmt"
"golang.org/x/crypto/bn256"
)
func main() {
g := bn256.G1{}
fmt.Println(g.String())
}
Change-Id: Ied6f7c8197e7b79b0913c000a9cf1cf68f8188a9
GitHub-Last-Rev: 23246486a982ea54d6023726e048c74f02089f25
GitHub-Pull-Request: golang/crypto#75
Reviewed-on: https://go-review.googlesource.com/c/163118
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Filippo Valsorda <filippo@golang.org>
diff --git a/bn256/bn256.go b/bn256/bn256.go
index b081c6a..9c99fcd 100644
--- a/bn256/bn256.go
+++ b/bn256/bn256.go
@@ -56,6 +56,9 @@
}
func (e *G1) String() string {
+ if e.p == nil {
+ return "bn256.G1" + newCurvePoint(nil).String()
+ }
return "bn256.G1" + e.p.String()
}
@@ -178,6 +181,9 @@
}
func (e *G2) String() string {
+ if e.p == nil {
+ return "bn256.G2" + newTwistPoint(nil).String()
+ }
return "bn256.G2" + e.p.String()
}
@@ -281,8 +287,11 @@
p *gfP12
}
-func (g *GT) String() string {
- return "bn256.GT" + g.p.String()
+func (e *GT) String() string {
+ if e.p == nil {
+ return "bn256.GT" + newGFp12(nil).String()
+ }
+ return "bn256.GT" + e.p.String()
}
// ScalarMult sets e to a*k and then returns e.