feat: Authenticate the API with a bearer token as well as a cookie

One middleware, two ways to arrive at the same *Session, so every handler,
role guard, licence gate and audit call is untouched. The host guard
applies to both: a token carries an instance, and the tenant boundary must
not have a token-shaped hole in it.

The effective role is min(user, token) recomputed per request, so demoting
somebody demotes their tokens with them. A stale cookie beside a valid
bearer falls through rather than refusing a credential that would work.

server/internal/auth/middleware.go

@@ -1,8 +1,12 @@
 package auth
 
 import (
+	"errors"
+	"fmt"
 	"net/http"
+	"strings"
 
+	"gitea.hostxtra.co.uk/mrhid6/vantage/server/internal/services"
 	"github.com/gin-gonic/gin"
 )
 
@@ -48,17 +52,20 @@ func RequireRole(roles ...string) gin.HandlerFunc {
 	}
 }
 
+// Middleware authenticates a request by session cookie or by API token.
+//
+// Both paths end by putting a *Session in the context, which is why no handler,
+// role guard, licence gate or audit call needed changing: the token path is a
+// second way to arrive at the same value, not a second way through the API.
 func Middleware() gin.HandlerFunc {
 	return func(c *gin.Context) {
-		cookie, err := c.Request.Cookie(sessionCookieName)
-		if err != nil {
-			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "not authenticated"})
-			return
+		sess, ok := sessionFromCookie(c)
+		if !ok {
+			sess, ok = sessionFromToken(c)
 		}
-
-		sess, err := GetSession(c.Request.Context(), cookie.Value)
-		if err != nil {
-			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "session expired"})
+		if !ok {
+			// sessionFromCookie and sessionFromToken have already written the
+			// response describing which credential failed and why.
 			return
 		}
 
@@ -69,6 +76,8 @@ func Middleware() gin.HandlerFunc {
 
 		c.Set(ctxSessionKey, sess)
 
+		// The host guard applies to both credential kinds. A token carries an
+		// instance, and the tenant boundary must not have a token-shaped hole.
 		if hostInstance, ok := InstanceFromHost(c); ok && hostInstance.InstanceID != sess.InstanceID {
 			c.AbortWithStatusJSON(http.StatusForbidden, gin.H{"error": "instance host mismatch"})
 			return
@@ -77,3 +86,105 @@ func Middleware() gin.HandlerFunc {
 		c.Next()
 	}
 }
+
+// sessionFromCookie returns false without writing a response when there is no
+// cookie at all, so the token path gets its turn. It writes and aborts only
+// when a cookie was presented and was not usable.
+func sessionFromCookie(c *gin.Context) (*Session, bool) {
+	cookie, err := c.Request.Cookie(sessionCookieName)
+	if err != nil {
+		return nil, false
+	}
+	sess, err := GetSession(c.Request.Context(), cookie.Value)
+	if err != nil {
+		// A stale cookie plus a valid bearer token is a real combination —
+		// a browser tab left open beside a curl. Fall through rather than
+		// refusing a credential that would have worked.
+		if bearerToken(c) != "" {
+			return nil, false
+		}
+		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "session expired"})
+		return nil, false
+	}
+	return sess, true
+}
+
+func bearerToken(c *gin.Context) string {
+	const prefix = "Bearer "
+	h := c.GetHeader("Authorization")
+	if len(h) <= len(prefix) || !strings.EqualFold(h[:len(prefix)], prefix) {
+		return ""
+	}
+	return h[len(prefix):]
+}
+
+func sessionFromToken(c *gin.Context) (*Session, bool) {
+	raw := bearerToken(c)
+	if raw == "" {
+		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "not authenticated"})
+		return nil, false
+	}
+
+	tok, err := services.ResolveAPIToken(raw)
+	if errors.Is(err, services.ErrTokenExpired) {
+		// Recorded rather than only refused: an expired token still being
+		// presented is how a forgotten CI job becomes visible.
+		services.LogEvent(tok.InstanceID, "token.expired_use", tok.Name, "", "",
+			fmt.Sprintf("expired token '%s' was used", tok.Name))
+		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "token expired", "code": "token_expired"})
+		return nil, false
+	}
+	if err != nil {
+		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
+		return nil, false
+	}
+
+	user, err := services.GetUserInInstance(tok.InstanceID, tok.UserID)
+	if err != nil {
+		// The owner is gone. DeleteUser removes tokens, so this is the
+		// belt-and-braces path for a row deleted some other way.
+		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
+		return nil, false
+	}
+
+	services.TouchAPIToken(tok)
+
+	return &Session{
+		UserID:     tok.UserID,
+		InstanceID: tok.InstanceID,
+		// Recomputed per request, so demoting the person demotes the token.
+		Role:      services.LowerRole(user.Role, tok.Role),
+		Email:     user.Email,
+		Name:      user.Email,
+		TokenID:   tok.TokenID,
+		TokenName: tok.Name,
+		Scopes:    tok.Scopes,
+	}, true
+}
+
+// TokenID is empty for a cookie session and the token's ID for a token
+// request. It is what lets audit detail record which credential acted.
+func TokenID(c *gin.Context) string {
+	if s := GetSessionFromContext(c); s != nil {
+		return s.TokenID
+	}
+	return ""
+}
+
+func TokenName(c *gin.Context) string {
+	if s := GetSessionFromContext(c); s != nil {
+		return s.TokenName
+	}
+	return ""
+}
+
+func Scopes(c *gin.Context) []string {
+	if s := GetSessionFromContext(c); s != nil {
+		return s.Scopes
+	}
+	return nil
+}
+
+// IsToken reports whether this request authenticated with an API token rather
+// than a browser session.
+func IsToken(c *gin.Context) bool { return TokenID(c) != "" }

server/internal/auth/session.go

@@ -22,6 +22,14 @@ type Session struct {
 	Role       string `json:"role"`
 	Email      string `json:"email"`
 	Name       string `json:"name"`
+
+	// The three fields below are set only when the request authenticated with
+	// an API token. They are never persisted to Redis — a token authenticates
+	// per request and mints no session, so a revoked token stops working
+	// immediately rather than at the end of a session TTL.
+	TokenID   string   `json:"-"`
+	TokenName string   `json:"-"`
+	Scopes    []string `json:"-"`
 }
 
 var rdb *redis.Client