Make API auth contexts safe to copy across threads

README.md

@@ -19,6 +19,24 @@ packages repository]. The url is
 [nimble configuration]: https://github.com/nim-lang/nimble#configuration
 [JDB Software Nim packages]: https://git.jdb-software.com/jdb/nim-packages
 
+## Authentication contexts and threads
+
+`ApiAuthContext` is a value object. Assigning it copies its configuration and
+signing-key cache, so each worker can own a context and refresh keys independently.
+Copy it before handing it to a worker, and synchronize any access to a context
+that another thread may be modifying.
+
+Use a `var ApiAuthContext` for `addSigningKeys`, `findSigningKey`, `validateJWT`,
+and `extractValidJwt`: lookup and validation can fetch and cache issuer keys.
+`createSignedJWT`, `newApiAccessToken`, and `createSessionCookies` also accept
+immutable contexts. Existing callers using `let` for a context that validates
+tokens must switch to `var`; use `Option[ApiAuthContext]` instead of `nil` when
+absence needs to be represented.
+
+The cache stores keys directly in a `Table[string, JwkSet]`, using the value
+semantics provided by `jwt_full` 0.5.0 or later. Context copies own independent
+key caches, and key lookup and signing use the parsed keys directly.
+
 ## License
 
 Buffoonery is available under two licenses depending on usage.

buffoonery.nimble

@@ -1,8 +1,8 @@
 # Package
 
-version       = "0.4.11"
+version       = "0.5.0"
 author        = "Jonathan Bernard"
-description   = "Jonathan's opinionated extensions and auth layer for Jester."
+description   = "Jonathan's opinionated extensions and auth layer for Mummy."
 license       = "MIT"
 srcDir        = "src"
 
@@ -15,7 +15,7 @@ requires "nim >= 1.6.2"
 requires @["bcrypt", "mummy", "uuids", "webby"]
 
 # from https://git.jdb-software.com/jdb/nim-packages
-requires @["jwt_full >= 0.2.0"]
+requires @["jwt_full >= 0.5.0"]
 
 task unittest, "Runs the unit test suite.":
   exec "nim c -r test/runner"

src/buffoonery/apierror.nim

@@ -3,7 +3,8 @@ import std/[httpcore, json, options, strutils]
 type ApiError* = object of CatchableError
   respMsg*: string
   respCode*: HttpCode
-  respData*: Option[JsonNode]
+  respData*: Option[JsonNode] # Optional data to include in API response
+  logData*: Option[JsonNode]  # Optional data to include in server-side logs
 
 
 proc newApiError*(
@@ -11,11 +12,13 @@ proc newApiError*(
     respCode: HttpCode,
     respMsg: string,
     respData = none[JsonNode](),
+    logData = none[JsonNode](),
     msg = ""): ref ApiError =
   result = newException(ApiError, msg, parent)
   result.respCode = respCode
   result.respMsg = respMsg
   result.respData = respData
+  result.logData = logData
 
   if not parent.isNil:
     result.trace &= parent.trace
@@ -25,12 +28,14 @@ proc raiseApiError*(
     respCode: HttpCode,
     respMsg: string,
     respData = none[JsonNode](),
+    logData = none[JsonNode](),
     msg = "") =
   var apiError = newApiError(
     parent = nil,
     respCode = respCode,
     respMsg = respMsg,
     respData = respData,
+    logData = logData,
     msg = if msg.isEmptyOrWhitespace: respMsg
           else: msg)
   raise apiError
@@ -41,6 +46,7 @@ proc raiseApiError*(
     parent: ref Exception,
     respMsg: string = "",
     respData = none[JsonNode](),
+    logData = none[JsonNode](),
     msg = "") =
   var apiError = newApiError(
     parent = parent,
@@ -49,6 +55,7 @@ proc raiseApiError*(
       if respMsg.isEmptyOrWhitespace: parent.msg
       else: respMsg,
     respData = respData,
+    logData = logData,
     msg =
       if msg.isEmptyOrWhitespace: parent.msg
       else: msg)

src/buffoonery/auth.nim

@@ -13,7 +13,10 @@ type
   AuthError* = object of CatchableError
     additionalInfo*: Option[TableRef[string, JsonNode]]
 
-  ApiAuthContext* = ref object
+  ApiAuthContext* = object
+    ## An owned authentication configuration and signing-key cache. Copy before
+    ## handing to a worker; each worker's cache updates stay local to its copy.
+    ## Concurrent access to the same mutable context still needs synchronization.
     appDomain*: string            ## Application domain for session cookies
     cookiePrefix*: string         ## Prefix for the user and session cookies
     validAudiences*: seq[string]  ## Expected audience values for for `aud` JWT check
@@ -26,7 +29,7 @@ type
       ## must be provided either when the ApiAuthContext is initialized (see
       ## `initApiAuthContext` or via `addSigningKeys`
 
-    issuerKeys: TableRef[string, JwkSet]
+    issuerKeys: Table[string, JwkSet]
 
 
 proc failAuth*[T](
@@ -71,7 +74,7 @@ proc initApiAuthContext*(
     issuer: issuer,
     trustedIssuers: trustedIssuers,
     signingKid: signingKid,
-    issuerKeys: newTable[string, JwkSet]([(issuer, signingKeys)]))
+    issuerKeys: toTable([(issuer, signingKeys)]))
 
 
 proc fetchJWKs(openIdConfigUrl: string): JwkSet {.gcsafe.} =
@@ -101,17 +104,16 @@ proc fetchJWKs(openIdConfigUrl: string): JwkSet {.gcsafe.} =
       parentException = getCurrentException())
 
 
-proc addSigningKeys*(ctx: ApiAuthContext, issuer: string, keySet: JwkSet): void =
+proc addSigningKeys*(ctx: var ApiAuthContext, issuer: string, keySet: JwkSet): void =
   ## Manually add a set of signing keys associated with a given issuer.
   try:
     for k in keySet: validateSigningKey(k)
-    if ctx.issuerKeys.isNil: ctx.issuerKeys = newTable[string, JwkSet]()
     ctx.issuerKeys[issuer] = keySet
   except:
     raise getCurrentException()
 
 
-proc findSigningKey*(ctx: ApiAuthContext, jwt: JWT, allowFetch = true): JWK {.gcsafe.} =
+proc findSigningKey*(ctx: var ApiAuthContext, jwt: JWT, allowFetch = true): JWK {.gcsafe.} =
   ## Lookup the signing key for a given JWT. This method assumes that you trust
   ## the issuer named in the JWT.
   ##
@@ -124,8 +126,6 @@ proc findSigningKey*(ctx: ApiAuthContext, jwt: JWT, allowFetch = true): JWK {.gc
     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]()
-
     let jwtIssuer = jwt.claims.iss.get
 
     if ctx.issuerKeys.hasKey(jwtIssuer):
@@ -151,7 +151,7 @@ proc findSigningKey*(ctx: ApiAuthContext, jwt: JWT, allowFetch = true): JWK {.gc
     failAuth("unable to find JWT signing key", getCurrentException())
 
 
-proc validateJWT*(ctx: ApiAuthContext, jwt: JWT) =
+proc validateJWT*(ctx: var 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:
@@ -195,7 +195,7 @@ proc validateJWT*(ctx: ApiAuthContext, jwt: JWT) =
     failAuth(getCurrentExceptionMsg(), getCurrentException())
 
 
-proc extractValidJwt*(ctx: ApiAuthContext, req: Request, validateCsrf = true): JWT =
+proc extractValidJwt*(ctx: var 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.

test/config.nims

@@ -1,2 +1,3 @@
 switch("path", "../src")
 switch("verbosity", "0")
+switch("threads", "on")

test/tauth.nim

@@ -0,0 +1,131 @@
+import std/[json, options, unittest]
+import jwt_full
+import buffoonery/auth
+
+const testIssuer = "https://issuer.example"
+
+proc keyNode(kid = "original"): JsonNode =
+  %*{"kty": "oct", "alg": "HS256", "kid": kid,
+     "k": "c2VjcmV0", "metadata": {"labels": ["original"]}}
+
+proc newContext(): ApiAuthContext =
+  initApiAuthContext("example.com", "test", @[testIssuer], testIssuer,
+    @[testIssuer], "original", @[initJwk(keyNode())])
+
+proc tokenFor(kid = "original", issuer = testIssuer): JWT =
+  # Lookup only needs the header and issuer; signing is tested separately.
+  createSignedJwt(initJoseHeader(%*{"alg": "HS256", "kid": kid}),
+    initJwtClaims(%*{"iss": issuer}), initJwk(keyNode(kid)))
+
+when compileOption("threads"):
+  type WorkerInput = tuple[ctx: ApiAuthContext, ok: ptr bool]
+
+  proc useContext(input: WorkerInput) {.thread.} =
+    var ctx = input.ctx
+    try:
+      ctx.validAudiences[0] = "worker"
+      let key = ctx.findSigningKey(tokenFor(), false)
+      key["metadata"].get["labels"][0].str = "worker"
+      ctx.addSigningKeys(testIssuer, @[initJwk(keyNode("worker"))])
+      input.ok[] = ctx.findSigningKey(tokenFor("worker"), false).kid.get == "worker"
+    except CatchableError:
+      input.ok[] = false
+
+suite "auth context value semantics":
+  test "copies own their configuration and signing-key cache":
+    var original = newContext()
+    var copied = original
+    copied.appDomain[0] = 'E'
+    copied.validAudiences[0][0] = 'H'
+    copied.trustedIssuers.add "https://other.example"
+    copied.addSigningKeys(testIssuer, @[initJwk(keyNode("replacement"))])
+
+    check original.appDomain == "example.com"
+    check original.validAudiences == @[testIssuer]
+    check original.trustedIssuers == @[testIssuer]
+    check original.findSigningKey(tokenFor(), false).kid.get == "original"
+    check copied.findSigningKey(tokenFor("replacement"), false).kid.get == "replacement"
+    expect AuthError:
+      discard copied.findSigningKey(tokenFor(), false)
+    expect AuthError:
+      discard original.findSigningKey(tokenFor("replacement"), false)
+
+  test "constructor and added keys do not retain caller-owned JSON":
+    let node = keyNode()
+    var ctx = initApiAuthContext("example.com", "test", @[testIssuer],
+      testIssuer, @[testIssuer], "original", @[initJwk(node)])
+    node["metadata"]["labels"][0].str = "changed"
+    check ctx.findSigningKey(tokenFor(), false)["metadata"].get["labels"][0].getStr == "original"
+
+    let added = keyNode("added")
+    ctx.addSigningKeys(testIssuer, @[initJwk(added)])
+    added["metadata"]["labels"][0].str = "changed"
+    check ctx.findSigningKey(tokenFor("added"), false)["metadata"].get["labels"][0].getStr == "original"
+
+  test "returned key metadata is independent of both context copies":
+    var original = newContext()
+    var copied = original
+    let key = copied.findSigningKey(tokenFor(), false)
+    key["metadata"].get["labels"][0].str = "changed"
+    check original.findSigningKey(tokenFor(), false)["metadata"].get["labels"][0].getStr == "original"
+    check copied.findSigningKey(tokenFor(), false)["metadata"].get["labels"][0].getStr == "original"
+
+  test "default contexts accept keys and reject missing keys without fetching":
+    var ctx: ApiAuthContext
+    expect AuthError:
+      discard ctx.findSigningKey(tokenFor(), false)
+    ctx.addSigningKeys(testIssuer, @[initJwk(keyNode())])
+    check ctx.findSigningKey(tokenFor(), false).kid.get == "original"
+
+  test "invalid key updates leave the existing cache intact":
+    var ctx = newContext()
+    let invalid = keyNode("invalid")
+    invalid.delete("alg")
+    expect AuthError:
+      ctx.addSigningKeys(testIssuer, @[initJwk(invalid)])
+    check ctx.findSigningKey(tokenFor(), false).kid.get == "original"
+
+  test "immutable contexts can sign tokens that mutable copies validate":
+    let original = newContext()
+    let token = original.newApiAccessToken("user")
+    var copied = original
+    copied.validateJWT(token)
+    check token.claims.sub.get == "user"
+
+  test "cached keys preserve RSA and EC variants":
+    var ctx: ApiAuthContext
+    let nodes = @[
+      %*{"kty": "RSA", "alg": "RS256", "kid": "rsa-public",
+         "n": "AQAB", "e": "AQAB"},
+      %*{"kty": "RSA", "alg": "RS256", "kid": "rsa-private",
+         "n": "AQAB", "e": "AQAB", "d": "Ag", "p": "Aw", "q": "BQ",
+         "oth": [{"r": "Bw", "d": "Ag", "t": "Aw"}]},
+      %*{"kty": "EC", "alg": "ES256", "kid": "ec-public",
+         "crv": "P-256", "x": "AQ", "y": "Ag"},
+      %*{"kty": "EC", "alg": "ES256", "kid": "ec-private",
+         "crv": "P-256", "x": "AQ", "y": "Ag", "d": "Aw"}]
+    for node in nodes:
+      let key = initJwk(node)
+      ctx.addSigningKeys(testIssuer, @[key])
+      let restored = ctx.findSigningKey(tokenFor(key.kid.get), false)
+      check restored.keyKind == key.keyKind
+      for name, value in node.pairs:
+        check restored[name].get == value
+      case key.keyKind
+      of RsaPublic: check restored.rsaPub == key.rsaPub
+      of RsaPrivate: check restored.rsaPrv == key.rsaPrv
+      of EcPublic: check restored.ecPub == key.ecPub
+      of EcPrivate: check restored.ecPrv == key.ecPrv
+      of Octet: discard
+
+  when compileOption("threads"):
+    test "workers mutate independent context copies":
+      var original = newContext()
+      var workers: array[2, Thread[WorkerInput]]
+      var succeeded: array[2, bool]
+      for i in 0 ..< workers.len:
+        createThread(workers[i], useContext, (original, addr succeeded[i]))
+      joinThreads(workers)
+      check succeeded == [true, true]
+      check original.validAudiences == @[testIssuer]
+      check original.findSigningKey(tokenFor(), false)["metadata"].get["labels"][0].getStr == "original"