Documentation
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Overview ¶
Package token generates and checks opaque bearer tokens.
A token has the shape "<prefix>_<body>": prefix is 2 to 12 characters from [a-z0-9] and body is 43 base62 characters drawn uniformly with crypto/rand, which carries 256 bits of entropy. Applications store only the SHA-256 Hash of a token and look it up by that digest.
The prefix tells token kinds apart. With an application prefix such as "app":
- API key: "app_"
- OAuth access token: "appat_"
- OAuth refresh token: "apprt_"
- session: "apps_"
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Check ¶
Check reports whether value has the given prefix and a well-formed body: the separator, exactly 43 base62 characters, nothing else. Use it before hashing so garbage never reaches the database.
func Hash ¶
Hash returns the SHA-256 digest of value. It is deterministic and unsalted: values carry 256 bits of entropy so neither brute force nor precomputation applies, and the digest is what the store looks up by.
func Prefix ¶
Prefix returns the part before the first "_", and false when value has no "_" or the prefix is empty.
func ValidPrefix ¶
ValidPrefix reports whether prefix matches ^[a-z0-9]{2,12}$. Packages that derive token prefixes from configuration validate them with this rule.
Types ¶
type Token ¶
Token is a freshly generated credential. Value is shown to the user once. Hash is what the application stores. Hint is the last four characters of Value, safe to show in lists.
func Generate ¶
Generate returns a token "<prefix>_<body>". body is 43 characters from the base62 alphabet [0-9A-Za-z], drawn uniformly with crypto/rand, so it holds 256 bits of entropy. prefix must match ^[a-z0-9]{2,12}$ and may itself contain no "_". Returns ez.EINVALID for a bad prefix, ez.EINTERNAL when the random source fails.
Source Files