[release-branch.go1.13-security] src/go.mod: import x/crypto/cryptobyte security fix for 32-bit archs

    cryptobyte: fix panic due to malformed ASN.1 inputs on 32-bit archs

    When int is 32 bits wide (on 32-bit architectures like 386 and arm), an
    overflow could occur, causing a panic, due to malformed ASN.1 being
    passed to any of the ASN1 methods of String.

    Tested on linux/386 and darwin/amd64.

    This fixes CVE-2020-7919 and was found thanks to the Project Wycheproof
    test vectors.

    Change-Id: I8c9696a8bfad1b40ec877cd740dba3467d66ab54
    Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/645211
    Reviewed-by: Katie Hockman <katiehockman@google.com>
    Reviewed-by: Adam Langley <agl@google.com>

x/crypto/cryptobyte is used in crypto/x509 for parsing certificates.
Malformed certificates might cause a panic during parsing on 32-bit
architectures (like arm and 386).

Change-Id: I840feb54eba880dbb96780ef7adcade073c4c4e3
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/647741
Reviewed-by: Katie Hockman <katiehockman@google.com>

5 files changed, 8 insertions, 12 deletions

diff --git a/src/go.mod b/src/go.mod
index 90af2a7ea0..9c9026f0d8 100644
--- a/src/go.mod
+++ b/src/go.mod
@@ -3,7 +3,7 @@ module std
 go 1.12
 
 require (
-	golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8
+	golang.org/x/crypto v0.0.0-20200124225646-8b5121be2f68
 	golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7
 	golang.org/x/sys v0.0.0-20190529130038-5219a1e1c5f8 // indirect
 	golang.org/x/text v0.3.2 // indirect
diff --git a/src/go.sum b/src/go.sum
index e358118e4c..e408f66328 100644
--- a/src/go.sum
+++ b/src/go.sum
@@ -1,6 +1,6 @@
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8 h1:1wopBVtVdWnn03fZelqdXTqk7U7zPQCb+T4rbU9ZEoU=
-golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/crypto v0.0.0-20200124225646-8b5121be2f68 h1:WPLCzSEbawp58wezcvLvLnvhiDJAai54ESbc41NdXS0=
+golang.org/x/crypto v0.0.0-20200124225646-8b5121be2f68/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7 h1:fHDIZ2oxGnUZRN6WgWFCbYBjH9uqVPRCUVUDhs0wnbA=
 golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
diff --git a/src/vendor/golang.org/x/crypto/cryptobyte/asn1.go b/src/vendor/golang.org/x/crypto/cryptobyte/asn1.go
index 528b9bff67..f930f7e526 100644
--- a/src/vendor/golang.org/x/crypto/cryptobyte/asn1.go
+++ b/src/vendor/golang.org/x/crypto/cryptobyte/asn1.go
@@ -470,7 +470,8 @@ func (s *String) ReadASN1GeneralizedTime(out *time.Time) bool {
 // It reports whether the read was successful.
 func (s *String) ReadASN1BitString(out *encoding_asn1.BitString) bool {
 	var bytes String
-	if !s.ReadASN1(&bytes, asn1.BIT_STRING) || len(bytes) == 0 {
+	if !s.ReadASN1(&bytes, asn1.BIT_STRING) || len(bytes) == 0 ||
+		len(bytes)*8/8 != len(bytes) {
 		return false
 	}
 
@@ -740,7 +741,7 @@ func (s *String) readASN1(out *String, outTag *asn1.Tag, skipHeader bool) bool {
 		length = headerLen + len32
 	}
 
-	if uint32(int(length)) != length || !s.ReadBytes((*[]byte)(out), int(length)) {
+	if int(length) < 0 || !s.ReadBytes((*[]byte)(out), int(length)) {
 		return false
 	}
 	if skipHeader && !out.Skip(int(headerLen)) {
diff --git a/src/vendor/golang.org/x/crypto/cryptobyte/string.go b/src/vendor/golang.org/x/crypto/cryptobyte/string.go
index 39bf98aeea..589d297e6b 100644
--- a/src/vendor/golang.org/x/crypto/cryptobyte/string.go
+++ b/src/vendor/golang.org/x/crypto/cryptobyte/string.go
@@ -24,7 +24,7 @@ type String []byte
 // read advances a String by n bytes and returns them. If less than n bytes
 // remain, it returns nil.
 func (s *String) read(n int) []byte {
-	if len(*s) < n {
+	if len(*s) < n || n < 0 {
 		return nil
 	}
 	v := (*s)[:n]
@@ -105,11 +105,6 @@ func (s *String) readLengthPrefixed(lenLen int, outChild *String) bool {
 		length = length << 8
 		length = length | uint32(b)
 	}
-	if int(length) < 0 {
-		// This currently cannot overflow because we read uint24 at most, but check
-		// anyway in case that changes in the future.
-		return false
-	}
 	v := s.read(int(length))
 	if v == nil {
 		return false
diff --git a/src/vendor/modules.txt b/src/vendor/modules.txt
index 453a312661..cff8acd02e 100644
--- a/src/vendor/modules.txt
+++ b/src/vendor/modules.txt
@@ -1,4 +1,4 @@
-# golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8
+# golang.org/x/crypto v0.0.0-20200124225646-8b5121be2f68
 golang.org/x/crypto/chacha20poly1305
 golang.org/x/crypto/cryptobyte
 golang.org/x/crypto/cryptobyte/asn1