Merge pull request #5 from sam80180/master

fix: finish RSA public key authentication

.gitignore

@@ -1,2 +1,6 @@
 .idea/
+.vscode/
 dist/
+vendor/
+sonic-android-supply
+sonic-android-supply.exe

Dockerfile_build

@@ -0,0 +1,11 @@
+FROM centos:7.6.1810
+WORKDIR /app
+ENV CGO_ENABLED=1 GO111MODULE=on GOPATH=/go GOOS=linux GOLANG_VERSION=1.20.14 \
+    PATH=/go/bin:/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+RUN yum install -y gcc openssl-devel; \
+    cd /tmp; curl https://dl.google.com/go/go${GOLANG_VERSION}.linux-amd64.tar.gz --output go.tar.gz; tar -C /usr/local -xzf go.tar.gz; rm -f go.tar.gz
+#CMD ["/bin/bash"]
+CMD ["/bin/bash", "-c", "go mod tidy; go mod vendor; go build"]
+
+# References:
+# https://www.ovhcloud.com/en-gb/community/tutorials/how-to-install-go-centos/

docker-compose.yml

@@ -0,0 +1,11 @@
+version: "3"
+services:
+  build_sas:
+    build:
+      context: "."
+      dockerfile: "./Dockerfile_build"
+    container_name: "build_sas"
+    image: "build_sas"
+    tty: true
+    volumes:
+    - ".:/app"

go.mod

@@ -1,15 +1,34 @@
 module github.com/SonicCloudOrg/sonic-android-supply
 
-go 1.18
+go 1.20
 
 require (
-	github.com/goinggo/mapstructure v0.0.0-20140717182941-194205d9b4a9
+	github.com/0xc0d/encoding v0.1.0
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
-	github.com/pkg/errors v0.8.0
+	github.com/pkg/errors v0.9.1
 	github.com/spf13/cobra v1.4.0
+	github.com/spf13/viper v1.18.2
 )
 
 require (
+	github.com/fsnotify/fsnotify v1.7.0 // indirect
+	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.0.0 // indirect
+	github.com/magiconair/properties v1.8.7 // indirect
+	github.com/mitchellh/mapstructure v1.5.0 // indirect
+	github.com/pelletier/go-toml/v2 v2.1.0 // indirect
+	github.com/sagikazarmark/locafero v0.4.0 // indirect
+	github.com/sagikazarmark/slog-shim v0.1.0 // indirect
+	github.com/sourcegraph/conc v0.3.0 // indirect
+	github.com/spf13/afero v1.11.0 // indirect
+	github.com/spf13/cast v1.6.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/subosito/gotenv v1.6.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	go.uber.org/multierr v1.9.0 // indirect
+	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
+	golang.org/x/sys v0.15.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	gopkg.in/ini.v1 v1.67.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,16 +1,76 @@
+github.com/0xc0d/encoding v0.1.0 h1:doSPUQU7EAeDEyk1RKUrodin+7V0Fv2PeQE0izJOUYo=
+github.com/0xc0d/encoding v0.1.0/go.mod h1:kmh8I0sB3CBTNeJfu8ryX4IQUuJBMoPmkGMD94Sam/4=
+github.com/bits-and-blooms/bitset v1.2.0/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
 github.com/cpuguy83/go-md2man/v2 v2.0.1/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
-github.com/goinggo/mapstructure v0.0.0-20140717182941-194205d9b4a9 h1:wqckanyE9qc/XnvnybC6SHOb8Nyd62QXAZOzA8twFig=
-github.com/goinggo/mapstructure v0.0.0-20140717182941-194205d9b4a9/go.mod h1:64ikIrMv84B+raz7akXOqbF7cK3/OQQ/6cClY10oy7A=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
+github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
+github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
+github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
 github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 h1:Z9n2FFNUXsshfwJMBgNA0RU6/i7WVaAegv3PtuIHPMs=
 github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51/go.mod h1:CzGEWj7cYgsdH8dAjBGEr58BoE7ScuLd+fwFZ44+/x8=
-github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
-github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0VQdvPDY=
+github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
+github.com/mitchellh/mapstructure v1.5.0 h1:jeMsZIYE/09sWLaz43PL7Gy6RuMjD2eJVyuac5Z2hdY=
+github.com/mitchellh/mapstructure v1.5.0/go.mod h1:bFUtVrKA4DC2yAKiSyO/QUcy7e+RRV2QTWOzhPopBRo=
+github.com/pelletier/go-toml/v2 v2.1.0 h1:FnwAJ4oYMvbT/34k9zzHuZNrhlz48GB3/s6at6/MHO4=
+github.com/pelletier/go-toml/v2 v2.1.0/go.mod h1:tJU2Z3ZkXwnxa4DPO899bsyIoywizdUvyaeZurnPPDc=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
+github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/sagikazarmark/locafero v0.4.0 h1:HApY1R9zGo4DBgr7dqsTH/JJxLTTsOt7u6keLGt6kNQ=
+github.com/sagikazarmark/locafero v0.4.0/go.mod h1:Pe1W6UlPYUk/+wc/6KFhbORCfqzgYEpgQ3O5fPuL3H4=
+github.com/sagikazarmark/slog-shim v0.1.0 h1:diDBnUNK9N/354PgrxMywXnAwEr1QZcOr6gto+ugjYE=
+github.com/sagikazarmark/slog-shim v0.1.0/go.mod h1:SrcSrq8aKtyuqEI1uvTDTK1arOWRIczQRv+GVI1AkeQ=
+github.com/sourcegraph/conc v0.3.0 h1:OQTbbt6P72L20UqAkXXuLOj79LfEanQ+YQFNpLA9ySo=
+github.com/sourcegraph/conc v0.3.0/go.mod h1:Sdozi7LEKbFPqYX2/J+iBAM6HpqSLTASQIKqDmF7Mt0=
+github.com/spf13/afero v1.11.0 h1:WJQKhtpdm3v2IzqG8VMqrr6Rf3UYpEF239Jy9wNepM8=
+github.com/spf13/afero v1.11.0/go.mod h1:GH9Y3pIexgf1MTIWtNGyogA5MwRIDXGUr+hbWNoBjkY=
+github.com/spf13/cast v1.6.0 h1:GEiTHELF+vaR5dhz3VqZfFSzZjYbgeKDpBxQVS4GYJ0=
+github.com/spf13/cast v1.6.0/go.mod h1:ancEpBxwJDODSW/UG4rDrAqiKolqNNh2DX3mk86cAdo=
 github.com/spf13/cobra v1.4.0 h1:y+wJpx64xcgO1V+RcnwW0LEHxTKRi2ZDPSBjWnrg88Q=
 github.com/spf13/cobra v1.4.0/go.mod h1:Wo4iy3BUC+X2Fybo0PDqwJIv3dNRiZLHQymsfxlB84g=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/spf13/viper v1.18.2 h1:LUXCnvUvSM6FXAsj6nnfc8Q2tp1dIgUfY9Kc8GsSOiQ=
+github.com/spf13/viper v1.18.2/go.mod h1:EKmWIqdnk5lOcmR72yw6hS+8OPYcwD0jteitLMVB+yk=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/subosito/gotenv v1.6.0 h1:9NlTDc1FTs4qu0DDq7AEtTPNw6SVm7uBMsUCUjABIf8=
+github.com/subosito/gotenv v1.6.0/go.mod h1:Dk4QP5c2W3ibzajGcXpNraDfq2IrhjMIvMSWPKKo0FU=
+go.uber.org/atomic v1.9.0 h1:ECmE8Bn/WFTYwEW/bpKD3M8VtR/zQVbavAoalC1PYyE=
+go.uber.org/atomic v1.9.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
+go.uber.org/multierr v1.9.0 h1:7fIwc/ZtS0q++VgcfqFDxSBZVv/Xo49/SYnDFupUwlI=
+go.uber.org/multierr v1.9.0/go.mod h1:X2jQV1h+kxSjClGpnseKVIxpmcjrj7MNnI0bnlfKTVQ=
+golang.org/x/exp v0.0.0-20230905200255-921286631fa9 h1:GoHiUyI/Tp2nVkLI2mCxVkOjsbSXD66ic0XW0js0R9g=
+golang.org/x/exp v0.0.0-20230905200255-921286631fa9/go.mod h1:S2oDrQGGwySpoQPVqRShND87VCbxmc6bL1Yd2oYrm6k=
+golang.org/x/sys v0.15.0 h1:h48lPFYpsTvQJZF4EKyI4aLHaev3CxivZmv7yZig9pc=
+golang.org/x/sys v0.15.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
+golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
+gopkg.in/ini.v1 v1.67.0 h1:Dgnx+6+nfE+IfzjUEISNeydPJh9AXNNsWbGP9KzCsOA=
+gopkg.in/ini.v1 v1.67.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=
 gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

src/adb/my_rsa_funcs.c

@@ -0,0 +1,27 @@
+#include <openssl/bio.h>
+#include <openssl/err.h>
+#include <openssl/obj_mac.h>
+#include <openssl/pem.h>
+#include <openssl/rsa.h>
+#include <stdio.h>
+#include <string.h>
+#include "my_rsa_funcs.h"
+
+char last_error_string[2048] = {0};
+
+int rsa_public_verify(unsigned char *m, unsigned char *sigbuf, unsigned char* strPEMPubKey) {
+    BIO *bio = BIO_new_mem_buf(strPEMPubKey, strlen(strPEMPubKey));
+    RSA *public_key = PEM_read_bio_RSA_PUBKEY(bio, NULL, NULL, NULL);
+    int n = RSA_verify(NID_sha1, m, strlen(m), sigbuf, strlen(sigbuf), public_key);
+    if (n==-1) {
+        snprintf(last_error_string, sizeof(last_error_string), "%s", ERR_error_string(ERR_get_error(), NULL));
+    } // end if
+    RSA_free(public_key);
+    return n;
+} // end rsa_public_verify()
+
+/*
+References:
+https://www.openssl.org/docs/man3.0/man3/RSA_verify.html
+https://android.googlesource.com/platform/packages/modules/adb/+/refs/heads/main/daemon/auth.cpp#177
+*/

src/adb/my_rsa_funcs.h

@@ -0,0 +1,3 @@
+extern char last_error_string[2048];
+
+int rsa_public_verify(unsigned char *, unsigned char *, unsigned char *);

src/adb/packet.go

@@ -2,11 +2,13 @@ package adb
 
 import (
 	"bytes"
+	"encoding/base64"
 	"encoding/binary"
 	"encoding/hex"
 	"fmt"
 	"io"
 	"os"
+	"regexp"
 	"strconv"
 )
 
@@ -79,3 +81,12 @@ func (pkt Packet) DumpToStdout() {
 	dumper.Write(pkt.Body)
 	dumper.Close()
 }
+
+func (pkt *Packet) ExtractADBRSAPublicKeyFromPayload() ([]byte, error) {
+	REGEX_ADB_PUBKEY := regexp.MustCompile(`(?m)^((?:[A-Za-z0-9+\/]{4})*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)?)\x00?(\s.*\s*)?$`) // https://github.com/openstf/stf/issues/1030#issuecomment-479487994
+	trimmedBody := pkt.BodySkipNull()
+	if !REGEX_ADB_PUBKEY.Match(trimmedBody) {
+		return nil, fmt.Errorf("unrecognizable public key format")
+	} // end if
+	return base64.StdEncoding.DecodeString(string(REGEX_ADB_PUBKEY.FindSubmatch(trimmedBody)[1]))
+} // end ExtractADBRSAPublicKeyFromPayload()

src/adb/pubkey.go

@@ -0,0 +1,120 @@
+package adb
+
+/*
+#cgo CFLAGS: -I/usr/local/opt/openssl/include
+#cgo LDFLAGS: -L/usr/include/openssl -Lmy/library/src -lcrypto
+#include "my_rsa_funcs.h"
+*/
+import "C"
+
+import (
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/binary"
+	"encoding/pem"
+	"fmt"
+	"math/big"
+	"unsafe"
+
+	"github.com/0xc0d/encoding/bytebuffer"
+)
+
+var ANDROID_PUBKEY_MODULUS_SIZE int = 2048 / 8
+var ANDROID_PUBKEY_ENCODED_SIZE int = 3*4 + 2*ANDROID_PUBKEY_MODULUS_SIZE
+var ANDROID_PUBKEY_MODULUS_SIZE_WORDS int = ANDROID_PUBKEY_MODULUS_SIZE / 4
+var RSA_SHA_PKCS1_SIGNATURE_PADDING []byte = []byte{
+	0x00, 0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
+	0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00,
+	0x04, 0x14,
+}
+
+func swapEndianness(bytes []byte) []byte {
+	len := len(bytes)
+	out := make([]byte, len)
+	for i, _ := range bytes {
+		out[i] = bytes[len-i-1]
+	} // end for
+	return out
+} // end swapEndianness()
+
+func AdbPubKeyDecode(androidPubkey []byte) (*rsa.PublicKey, error) {
+	key_size := len(androidPubkey)
+	if key_size < ANDROID_PUBKEY_ENCODED_SIZE {
+		return nil, fmt.Errorf("invalid key length")
+	} // end if
+	keyStruct := bytebuffer.NewWrappedBuffer(androidPubkey, key_size)
+	keyStruct.SetOrder(binary.LittleEndian)
+	modulusSize, _ := keyStruct.GetAsInt32()
+	if int(modulusSize) != ANDROID_PUBKEY_MODULUS_SIZE_WORDS {
+		return nil, fmt.Errorf("invalid modulus length")
+	} // end if
+	modulus := make([]byte, ANDROID_PUBKEY_MODULUS_SIZE)
+	keyStruct.SetPosition(8)
+	keyStruct.GetBytes(modulus, 0, ANDROID_PUBKEY_MODULUS_SIZE)
+	n := new(big.Int)
+	n.SetBytes(swapEndianness(modulus))
+	keyStruct.SetPosition(520)
+	e, _ := keyStruct.GetAsInt32()
+	return &rsa.PublicKey{N: n, E: int(e)}, nil
+} // end AdbPubKeyDecode()
+/*
+	func RSA_public_decrypt(pubKey *rsa.PublicKey, data []byte) []byte {
+		// https://stackoverflow.com/a/44853488/12857692
+		c := new(big.Int)
+		m := new(big.Int)
+		m.SetBytes(data)
+		e := big.NewInt(int64(pubKey.E))
+		c.Exp(m, e, pubKey.N)
+		out := c.Bytes()
+		skip := 0
+		for i := 2; i < len(out); i++ {
+			if i+1 >= len(out) {
+				break
+			}
+			if out[i] == 0xff && out[i+1] == 0 {
+				skip = i + 2
+				break
+			}
+		}
+		return out[skip:]
+	}
+*/
+func publicKeyToPEM(pubkey *rsa.PublicKey) ([]byte, error) {
+	derBytes, _ := x509.MarshalPKIXPublicKey(pubkey)
+	pemBlock := &pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: derBytes,
+	}
+	pemBytes := pem.EncodeToMemory(pemBlock)
+	return pemBytes, nil
+} // end publicKeyToPEM()
+
+func PubKeyValidate(publicKey *rsa.PublicKey, digest, signature []byte) (bool, error) {
+	pem, _ := publicKeyToPEM(publicKey)
+	nVerify := C.rsa_public_verify((*C.uchar)(unsafe.Pointer(&digest[0])), (*C.uchar)(unsafe.Pointer(&signature[0])), (*C.uchar)(unsafe.Pointer(&pem[0])))
+	if nVerify != 0 {
+		return false, fmt.Errorf("%s", C.GoString(&C.last_error_string[0]))
+	} // end if
+	return true, nil
+} // end PubKeyValidate()
+
+/*
+References:
+https://github.com/MuntashirAkon/libadb-android/blob/master/libadb/src/main/java/io/github/muntashirakon/adb/AndroidPubkey.java
+*/