diff --git a/passgen/passgen.go b/passgen/passgen.go new file mode 100644 index 0000000..af19f55 --- /dev/null +++ b/passgen/passgen.go @@ -0,0 +1,62 @@ +// Package passgen generates random, unmemorable passwords. +// +// Example usage: +// +// p := passgen.New() // p is "6NX(W`GD]4:Tqk};Y@A-" +// +// Logic originally from dchest's uniuri library: +// https://github.com/dchest/uniuri +// +// Functions read from crypto/rand random source, and panic if they fail to +// read from it. +package passgen + +import "crypto/rand" + +// DefLen is the default password length returned. +const DefLen = 20 + +// DefChars is the default set of characters used in the password. +var DefChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*()- _=+,.?/:;{}[]`~") + +// New returns a random password of the default length with the default set of +// characters. +func New() string { + return NewLenChars(DefLen, DefChars) +} + +// NewLen returns a random password of the given length with the default set +// of characters. +func NewLen(length int) string { + return NewLenChars(length, DefChars) +} + +// NewLenChars returns a random password of the given length with the given +// set of characters. +func NewLenChars(length int, chars []byte) string { + if length == 0 { + return "" + } + clen := len(chars) + maxrb := 255 - (256 % clen) + b := make([]byte, length) + r := make([]byte, length+(length/4)) // storage for random bytes. + i := 0 + for { + if _, err := rand.Read(r); err != nil { + panic("passgen: error reading random bytes: " + err.Error()) + } + for _, rb := range r { + c := int(rb) + if c > maxrb { + // Skip this number to avoid modulo bias. + continue + } + b[i] = chars[c%clen] + i++ + if i == length { + return string(b) + } + } + } +}