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| 1 | +// SPDX-License-Identifier: AGPL-3.0-or-later |
| 2 | + |
| 3 | +package githttp |
| 4 | + |
| 5 | +import ( |
| 6 | + "context" |
| 7 | + "encoding/base64" |
| 8 | + "errors" |
| 9 | + "strings" |
| 10 | + "time" |
| 11 | + |
| 12 | + "github.com/tenseleyFlow/shithub/internal/auth/pat" |
| 13 | + "github.com/tenseleyFlow/shithub/internal/auth/password" |
| 14 | +) |
| 15 | + |
| 16 | +// resolvedAuth carries the resolved identity for a git-over-HTTPS |
| 17 | +// request. Anonymous = true is the "no Authorization header" case; |
| 18 | +// callers decide whether anonymous is allowed (yes for pulling a public |
| 19 | +// repo, no for everything else). |
| 20 | +type resolvedAuth struct { |
| 21 | + Anonymous bool |
| 22 | + UserID int64 |
| 23 | + Username string |
| 24 | + ViaPAT bool |
| 25 | +} |
| 26 | + |
| 27 | +// errBadCredentials is the catch-all for "creds were sent but didn't |
| 28 | +// resolve." We DON'T distinguish the failure reasons (wrong username, |
| 29 | +// wrong password, revoked PAT, etc.) so the response is identical to |
| 30 | +// "no creds at all" — preventing username probes via timing/messaging. |
| 31 | +var errBadCredentials = errors.New("githttp: bad credentials") |
| 32 | + |
| 33 | +// resolveBasicAuth parses the Authorization header and resolves it |
| 34 | +// against the DB. Three outcomes: |
| 35 | +// |
| 36 | +// Anonymous=true, err=nil — no credentials supplied |
| 37 | +// Anonymous=false, err=nil — credentials matched a real user |
| 38 | +// Anonymous=false, err!=nil — credentials present but invalid |
| 39 | +// |
| 40 | +// PAT path is preferred when the secret carries the canonical |
| 41 | +// `shithub_pat_` prefix; password path is the fallback. A failed PAT |
| 42 | +// lookup falls through to password — if a user happens to set their |
| 43 | +// account password to a string that starts with our PAT prefix, we |
| 44 | +// still try to authenticate them. |
| 45 | +func (h *Handlers) resolveBasicAuth(ctx context.Context, header string) (resolvedAuth, error) { |
| 46 | + if header == "" { |
| 47 | + return resolvedAuth{Anonymous: true}, nil |
| 48 | + } |
| 49 | + scheme, rest, ok := strings.Cut(header, " ") |
| 50 | + if !ok || !strings.EqualFold(scheme, "Basic") { |
| 51 | + return resolvedAuth{}, errBadCredentials |
| 52 | + } |
| 53 | + decoded, err := base64.StdEncoding.DecodeString(strings.TrimSpace(rest)) |
| 54 | + if err != nil { |
| 55 | + return resolvedAuth{}, errBadCredentials |
| 56 | + } |
| 57 | + user, secret, ok := strings.Cut(string(decoded), ":") |
| 58 | + if !ok { |
| 59 | + return resolvedAuth{}, errBadCredentials |
| 60 | + } |
| 61 | + |
| 62 | + if strings.HasPrefix(secret, pat.Prefix) { |
| 63 | + if got, err := h.resolveViaPAT(ctx, secret); err == nil { |
| 64 | + return got, nil |
| 65 | + } |
| 66 | + // Fall through — a non-matching PAT prefix could still be a |
| 67 | + // user-chosen password. |
| 68 | + } |
| 69 | + return h.resolveViaPassword(ctx, user, secret) |
| 70 | +} |
| 71 | + |
| 72 | +// resolveViaPAT looks up the token by its sha256 hash, checks |
| 73 | +// revoked/expired/suspended, and returns the owning user. Returns |
| 74 | +// errBadCredentials on any failure (no leak about which check failed). |
| 75 | +func (h *Handlers) resolveViaPAT(ctx context.Context, raw string) (resolvedAuth, error) { |
| 76 | + hash, err := pat.HashOf(raw) |
| 77 | + if err != nil { |
| 78 | + return resolvedAuth{}, errBadCredentials |
| 79 | + } |
| 80 | + row, err := h.uq.GetUserTokenByHash(ctx, h.d.Pool, hash) |
| 81 | + if err != nil { |
| 82 | + return resolvedAuth{}, errBadCredentials |
| 83 | + } |
| 84 | + if row.RevokedAt.Valid { |
| 85 | + return resolvedAuth{}, errBadCredentials |
| 86 | + } |
| 87 | + if row.ExpiresAt.Valid && time.Now().After(row.ExpiresAt.Time) { |
| 88 | + return resolvedAuth{}, errBadCredentials |
| 89 | + } |
| 90 | + user, err := h.uq.GetUserByID(ctx, h.d.Pool, row.UserID) |
| 91 | + if err != nil || user.SuspendedAt.Valid { |
| 92 | + return resolvedAuth{}, errBadCredentials |
| 93 | + } |
| 94 | + return resolvedAuth{ |
| 95 | + UserID: user.ID, Username: user.Username, ViaPAT: true, |
| 96 | + }, nil |
| 97 | +} |
| 98 | + |
| 99 | +// resolveViaPassword verifies the supplied secret against the user's |
| 100 | +// argon2id hash. The username supplied in the Basic header is taken at |
| 101 | +// face value here — git's credential prompt typically asks "Username |
| 102 | +// for shithub:" and the user types their shithub username. |
| 103 | +// |
| 104 | +// Constant-time discipline: when the username doesn't exist we still |
| 105 | +// run VerifyAgainstDummy so the response time is the same as a wrong |
| 106 | +// password. |
| 107 | +func (h *Handlers) resolveViaPassword(ctx context.Context, username, secret string) (resolvedAuth, error) { |
| 108 | + if username == "" { |
| 109 | + // No way to look up; still burn time on a dummy to avoid timing leaks. |
| 110 | + password.VerifyAgainstDummy(secret) |
| 111 | + return resolvedAuth{}, errBadCredentials |
| 112 | + } |
| 113 | + user, err := h.uq.GetUserByUsername(ctx, h.d.Pool, username) |
| 114 | + if err != nil { |
| 115 | + password.VerifyAgainstDummy(secret) |
| 116 | + return resolvedAuth{}, errBadCredentials |
| 117 | + } |
| 118 | + if user.SuspendedAt.Valid || user.DeletedAt.Valid { |
| 119 | + password.VerifyAgainstDummy(secret) |
| 120 | + return resolvedAuth{}, errBadCredentials |
| 121 | + } |
| 122 | + ok, err := password.Verify(secret, user.PasswordHash) |
| 123 | + if err != nil || !ok { |
| 124 | + return resolvedAuth{}, errBadCredentials |
| 125 | + } |
| 126 | + return resolvedAuth{ |
| 127 | + UserID: user.ID, Username: user.Username, ViaPAT: false, |
| 128 | + }, nil |
| 129 | +} |
| 130 | + |