Log Message:
Update go115 to 1.15.5 (security fix).

   - math/big: panic during recursive division of very large numbers

A number of math/big.Int <https://pkg.go.dev/math/big#Int> methods (Div,
Exp, DivMod, Quo, Rem, QuoRem, Mod, ModInverse, ModSqrt, Jacobi, and GCD)
can panic when provided crafted large inputs. For the panic to happen, the
divisor or modulo argument must be larger than 3168 bits (on 32-bit
architectures) or 6336 bits (on 64-bit architectures). Multiple math/big.Rat
<https://pkg.go.dev/math/big#Rat> methods are similarly affected.

crypto/rsa.VerifyPSS <https://pkg.go.dev/crypto/rsa#VerifyPSS>,
crypto/rsa.VerifyPKCS1v15 <https://pkg.go.dev/crypto/rsa#VerifyPKCS1v15>,
and crypto/dsa.Verify <https://pkg.go.dev/crypto/dsa#Verify> may panic when
provided crafted public keys and signatures. crypto/ecdsa and
crypto/elliptic operations may only be affected if custom CurveParams
<https://pkg.go.dev/crypto/elliptic#CurveParams> with unusually large field
sizes (several times larger than the largest supported curve, P-521) are in
use. Using crypto/x509.Verify on a crafted X.509 certificate chain can lead
to a panic, even if the certificates don’t chain to a trusted root. The
chain can be delivered via a crypto/tls connection to a client, or to a
server that accepts and verifies client certificates. net/http clients can
be made to crash by an HTTPS server, while net/http servers that accept
client certificates will recover the panic and are unaffected.

Moreover, an application might crash invoking
crypto/x509.(*CertificateRequest).CheckSignature on an X.509 certificate
request or during a golang.org/x/crypto/otr conversation. Parsing a
golang.org/x/crypto/openpgp Entity or verifying a signature may crash.
Finally, a golang.org/x/crypto/ssh client can panic due to a malformed host
key, while a server could panic if either PublicKeyCallback accepts a
malformed public key, or if IsUserAuthority accepts a certificate with a
malformed public key.

This issue is CVE-2020-28362 and Go issue golang.org/issue/42552.

   - cmd/go: arbitrary code execution at build time through cgo

The go command may execute arbitrary code at build time when cgo is in use.
This may occur when running go get on a malicious package, or any other
command that builds untrusted code.

This can be caused by malicious gcc flags specified via a #cgo directive,
or by a malicious symbol name in a linked object file.

These issues are CVE-2020-28367 and CVE-2020-28366, and Go issues
golang.org/issue/42556 and golang.org/issue/42559 respectively.