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d4z3x/decrypt.go

Forked from apokalyptik/decrypt.go
Created June 5, 2020 00:43
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Revisions

  1. @apokalyptik apokalyptik created this gist Sep 1, 2014.
    55 changes: 55 additions & 0 deletions decrypt.go
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,55 @@
    package main

    import (
    "crypto/rand"
    "crypto/rsa"
    "crypto/x509"
    "encoding/pem"
    "flag"
    "fmt"
    "io/ioutil"
    "log"
    "os"
    )

    func main() {
    var PKPW string
    flag.StringVar(&PKPW, "pp", PKPW, "private key passphrase")
    flag.Parse()
    // Read the standard input
    in, err := ioutil.ReadAll(os.Stdin)
    if err != nil {
    log.Fatalf("input file: %s", err)
    }
    pemData, err := ioutil.ReadFile("pri.key")
    if err != nil {
    log.Fatalf("read key file: %s", err)
    }
    // Extract the PEM-encoded data block
    block, _ := pem.Decode(pemData)
    if block == nil {
    log.Fatalf("bad key data: %s", "not PEM-encoded")
    }
    if got, want := block.Type, "RSA PRIVATE KEY"; got != want {
    log.Fatalf("unknown key type %q, want %q", got, want)
    }
    if PKPW != "" {
    if decBlock, err := x509.DecryptPEMBlock(block, []byte(PKPW)); err != nil {
    log.Fatalf("error decrypting pem file: %s", err.Error())
    } else {
    block.Bytes = decBlock
    }
    }
    // Decode the RSA private key
    priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
    if err != nil {
    log.Fatalf("bad private key: %s", err)
    }
    // Decrypt the data
    out, err := rsa.DecryptPKCS1v15(rand.Reader, priv, in)
    if err != nil {
    log.Fatalf("decrypt: %s", err)
    }
    // Write data to output file
    fmt.Fprint(os.Stdout, string(out))
    }