Adds b64d

Author: tomnomnom

b64d/.gitignore

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+testfile
+b64d
+*.sw*

b64d/README.md

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+# b64d
+
+Find and decode base64-encoded strings in a file.
+
+## Usage
+
+```
+▶ b64d <filename>
+```
+
+## Install
+
+```
+▶ go get -u github.com/tomnomnom/hacks/b64d
+```

b64d/main.go

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+package main
+
+import (
+	"encoding/base64"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"regexp"
+	"strings"
+	"unicode"
+)
+
+var ASCIIChar = &unicode.RangeTable{
+	R16: []unicode.Range16{
+		{0x0020, 0x007F, 1},
+	},
+}
+
+func main() {
+	flag.Parse()
+
+	filename := flag.Arg(0)
+	if filename == "" {
+		fmt.Fprintln(os.Stderr, "usage: b64d <filename>")
+		return
+	}
+
+	f, err := os.Open(filename)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+		return
+	}
+
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+		return
+	}
+
+	content := string(b)
+
+	// TODO: deal with urlencoded bits
+	re := regexp.MustCompile("[^A-Za-z0-9+/][a-zA-Z0-9+/]+={0,2}")
+	matches := re.FindAllString(content, -1)
+
+	if matches == nil {
+		return
+	}
+
+	for _, m := range matches {
+
+		if len(m) < 7 {
+			continue
+		}
+
+		// match has one extra char at the beginning
+		if (len(m)-1)%4 != 0 {
+			continue
+		}
+		decb, _ := base64.StdEncoding.DecodeString(m[1:])
+		decoded := string(decb)
+		if decoded == "" {
+			continue
+		}
+
+		decoded = strings.Replace(decoded, "\n", " ", -1)
+
+		containsNonASCII := false
+		for _, r := range decoded {
+			if !unicode.Is(ASCIIChar, r) {
+				containsNonASCII = true
+				break
+			}
+		}
+		if containsNonASCII {
+			continue
+		}
+
+		fmt.Println(decoded)
+	}
+}