Add additional information to AuthErrors raised.

buffoonery.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "0.4.5"
+version       = "0.4.7"
 author        = "Jonathan Bernard"
 description   = "Jonathan's opinionated extensions and auth layer for Jester."
 license       = "MIT"

src/buffoonery.nim

@@ -1,5 +1,2 @@
-import buffoonery/apierror,
-       buffoonery/apiutils,
-       buffoonery/auth,
-       buffoonery/jsonutils
+import buffoonery/[apierror, apiutils, auth, jsonutils]
 export apierror, apiutils, auth, jsonutils

src/buffoonery/auth.nim

@@ -4,13 +4,14 @@ import std/httpclient except HttpHeaders
 
 import jwt_full, jwt_full/encoding
 
-import ./apiutils, ./jsonutils
+import ./[apiutils,jsonutils]
 
 const SUPPORTED_SIGNATURE_ALGORITHMS = @[ HS256, RS256 ]
 
 
 type
   AuthError* = object of CatchableError
+    additionalInfo*: Option[TableRef[string, JsonNode]]
 
   ApiAuthContext* = ref object
     appDomain*: string            ## Application domain for session cookies
@@ -28,6 +29,19 @@ type
     issuerKeys: TableRef[string, JwkSet]
 
 
+proc failAuth*[T](
+    reason: string,
+    additionalInfo: TableRef[string, T],
+    parentException: ref Exception = nil) =
+  ## Syntactic sugar to raise an AuthError. Reason will be the exception
+  ## message and should be considered an internal message.
+  let err = newException(AuthError, reason, parentException)
+  err.additionalInfo = some(newTable[string, JsonNode]())
+  for key, val in additionalInfo.pairs:
+    err.additionalInfo.get[key] = %val
+  raise err
+
+
 proc failAuth*(reason: string, parentException: ref Exception = nil) =
   ## Syntactic sugar to raise an AuthError. Reason will be the exception
   ## message and should be considered an internal message.
@@ -63,6 +77,7 @@ proc initApiAuthContext*(
 proc fetchJWKs(openIdConfigUrl: string): JwkSet {.gcsafe.} =
   ## Fetch signing keys for an OAuth issuer. `openIdConfigUrl` is expected to
   ## be a well-known URL (ISSUER_BASE/.well-known/openid-configuration)
+  var jwksKeysURI: string
   try:
     let http = newHttpClient()
 
@@ -70,14 +85,20 @@ proc fetchJWKs(openIdConfigUrl: string): JwkSet {.gcsafe.} =
     let metadata = parseJson(http.getContent(openIdConfigUrl))
 
     # Fetch the keys from the jwk_keys URI.
-    let jwksKeysURI = metadata.getOrFail("jwks_uri").getStr
+    jwksKeysURI = metadata.getOrFail("jwks_uri").getStr
     let jwksKeys = parseJson(http.getContent(jwksKeysURI))
 
     # Parse and load the keys provided.
     return initJwkSet(jwksKeys)
 
-  except:
-    failAuth("unable to fetch isser signing keys", getCurrentException())
+  except Exception:
+    #failAuth "unable to fetch isser signing keys"
+    failAuth(
+      reason = "unable to fetch isser signing keys",
+      additionalInfo = newTable[string, string]({
+        "openIdConfigUrl": openIdConfigUrl,
+        "jwksKeysURI": jwksKeysURI }),
+      parentException = getCurrentException())
 
 
 proc addSigningKeys*(ctx: ApiAuthContext, issuer: string, keySet: JwkSet): void =
@@ -100,8 +121,8 @@ proc findSigningKey*(ctx: ApiAuthContext, jwt: JWT, allowFetch = true): JWK {.gc
   ## [OpenID Connect standard discovery mechanism](https://openid.net/specs/openid-connect-discovery-1_0.html)
 
   try:
-    if jwt.claims.iss.isNone: failAuth "Missing 'iss' claim."
-    if jwt.header.kid.isNone: failAuth "Missing 'kid' header."
+    if jwt.claims.iss.isNone: failAuth "JWT is missing 'iss' claim."
+    if jwt.header.kid.isNone: failAuth "JWT is missing 'kid' header."
 
     if ctx.issuerKeys.isNil: ctx.issuerKeys = newTable[string, JwkSet]()
 
@@ -120,7 +141,11 @@ proc findSigningKey*(ctx: ApiAuthContext, jwt: JWT, allowFetch = true): JWK {.gc
         fetchJWKs(jwtIssuer & "/.well-known/openid-configuration")
       return ctx.findSigningKey(jwt, false)
 
-    failAuth "unable to find JWT signing key"
+    failAuth(
+      reason = "unable to find JWT signing key",
+      additionalInfo = newTable[string, string]({
+        "jwtIssuer": jwtIssuer,
+        "jwtKid": jwt.header.kid.get}))
 
   except:
     failAuth("unable to find JWT signing key", getCurrentException())
@@ -130,18 +155,21 @@ proc validateJWT*(ctx: ApiAuthContext, jwt: JWT) =
   ## Given a JWT, validate that it is a well-formed JWT, validate the issuer's
   ## signature on the token, and validate all the claims that it preesnts.
   try:
-    if jwt.claims.iss.isNone: failAuth "Missing 'iss' claim."
+    if jwt.claims.iss.isNone: failAuth "JWT is missing 'iss' claim."
     let jwtIssuer = jwt.claims.iss.get
 
     if not ctx.trustedIssuers.contains(jwtIssuer):
-      failAuth "JWT is issued by $# but we only trust $#" %
-        [jwtIssuer, $ctx.trustedIssuers]
+      failAuth(
+        reason = "We don't trust the JWT's issuer.",
+        additionalInfo = newTable[string, JsonNode]({
+          "issuer": %jwtIssuer,
+          "trustedIssuers": %ctx.trustedIssuers}))
 
-    if jwt.header.alg.isNone: failAuth "Missing 'alg' header property."
-    if jwt.claims.aud.isNone: failAuth "Missing 'aud' claim."
-    if jwt.claims.iss.isNone: failAuth "Missing 'iss' claim."
-    if jwt.claims.sub.isNone: failAuth "Missing 'sub' claim."
-    if jwt.claims.exp.isNone: failAuth "Missing or invalid 'exp' claim."
+    if jwt.header.alg.isNone: failAuth "JWT is missing 'alg' header property."
+    if jwt.claims.aud.isNone: failAuth "JWT is missing 'aud' claim."
+    if jwt.claims.iss.isNone: failAuth "JWT is missing 'iss' claim."
+    if jwt.claims.sub.isNone: failAuth "JWT is missing 'sub' claim."
+    if jwt.claims.exp.isNone: failAuth "JWT is missing or invalid 'exp' claim."
 
     if jwt.claims["aud"].get.kind == JString:
       # If the token is for a single audience, check that it is for us.
@@ -167,7 +195,7 @@ proc validateJWT*(ctx: ApiAuthContext, jwt: JWT) =
     failAuth(getCurrentExceptionMsg(), getCurrentException())
 
 
-proc extractValidJwt*(ctx: ApiAuthContext, req: Request): JWT =
+proc extractValidJwt*(ctx: ApiAuthContext, req: Request, validateCsrf = true): JWT =
   ## Extracts a valid JWT representing the user's authentication and
   ## authorization details, if present. If there are no valid credentials an
   ## exception is raised.
@@ -191,6 +219,12 @@ proc extractValidJwt*(ctx: ApiAuthContext, req: Request): JWT =
   ##
   ##   In the split-cookie mode we also check that the `csrfToken` claim in the
   ##   JWT payload matches the CSRF value passed via the `X-CSRF-TOKEN` header.
+  ##   This CSRF check can be disabled by setting `validateCsrf` to `false`.
+  ##   This option is proivded to support occasional use-cases where you want to
+  ##   be able to serve a request using cookie auth when the client can't set
+  ##   custom headers (e.g. a simple link from an <a> tag). Obviously, this is a
+  ##   security risk and should only be used with caution with a full
+  ##   understanding of the risk.
 
   try:
     if req.headers.contains("Authorization"):
@@ -214,12 +248,17 @@ proc extractValidJwt*(ctx: ApiAuthContext, req: Request): JWT =
 
       # Because this is a web session, check that the CSRF is present and
       # matches.
-      if not req.headers.contains("X-CSRF-TOKEN") or
-         not result.claims["csrfToken"].isSome:
-        failAuth "missing CSRF token"
+      if validateCsrf:
+        if not req.headers.contains("X-CSRF-TOKEN") or
+           not result.claims["csrfToken"].isSome:
+          failAuth "missing CSRF token"
 
-      if req.headers["X-CSRF-TOKEN"] != result.claims["csrfToken"].get.getStr(""):
-        failAuth "invalid CSRF token"
+        if req.headers["X-CSRF-TOKEN"] != result.claims["csrfToken"].get.getStr(""):
+          failAuth(
+            reason = "invalid CSRF token",
+            additionalInfo = newTable[string, string]({
+              "header": req.headers["X-CSRF-TOKEN"],
+              "jwt": result.claims["csrfToken"].get.getStr("")}))
 
     else: failAuth "no auth token, no Authorization or Cookie headers"