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Adds declared caveats to the discharge macaroon.
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// Copyright 2023 Canonical Ltd. | ||
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package jimm | ||
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import ( | ||
"context" | ||
"net/http" | ||
"strings" | ||
"time" | ||
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"github.com/go-macaroon-bakery/macaroon-bakery/v3/bakery" | ||
"github.com/go-macaroon-bakery/macaroon-bakery/v3/bakery/checkers" | ||
"github.com/go-macaroon-bakery/macaroon-bakery/v3/bakery/dbrootkeystore" | ||
"github.com/go-macaroon-bakery/macaroon-bakery/v3/httpbakery" | ||
jjmacaroon "github.com/juju/juju/core/macaroon" | ||
"github.com/juju/names/v4" | ||
"github.com/juju/zaputil/zapctx" | ||
"go.uber.org/zap" | ||
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"github.com/canonical/jimm/internal/db" | ||
"github.com/canonical/jimm/internal/dbmodel" | ||
"github.com/canonical/jimm/internal/errors" | ||
"github.com/canonical/jimm/internal/openfga" | ||
ofganames "github.com/canonical/jimm/internal/openfga/names" | ||
jimmnames "github.com/canonical/jimm/pkg/names" | ||
) | ||
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var defaultDischargeExpiry = 15 * time.Minute | ||
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func newMacaroonDischarger(p Params, db *db.Database, ofgaClient *openfga.OFGAClient) (*macaroonDischarger, error) { | ||
var kp bakery.KeyPair | ||
if p.PublicKey == "" || p.PrivateKey == "" { | ||
generatedKP, err := bakery.GenerateKey() | ||
if err != nil { | ||
return nil, errors.E(err, "failed to generate a bakery keypair") | ||
} | ||
kp = *generatedKP | ||
} else { | ||
if err := kp.Private.UnmarshalText([]byte(p.PrivateKey)); err != nil { | ||
return nil, errors.E(err, "cannot unmarshal private key") | ||
} | ||
if err := kp.Public.UnmarshalText([]byte(p.PublicKey)); err != nil { | ||
return nil, errors.E(err, "cannot unmarshal public key") | ||
} | ||
} | ||
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checker := checkers.New(jjmacaroon.MacaroonNamespace) | ||
b := bakery.New( | ||
bakery.BakeryParams{ | ||
Checker: checker, | ||
RootKeyStore: dbrootkeystore.NewRootKeys(100, nil).NewStore( | ||
db, | ||
dbrootkeystore.Policy{ | ||
ExpiryDuration: p.MacaroonExpiryDuration, | ||
}, | ||
), | ||
Key: &kp, | ||
Location: "jimm " + p.ControllerUUID, | ||
}, | ||
) | ||
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return &macaroonDischarger{ | ||
ofgaClient: ofgaClient, | ||
bakery: b, | ||
kp: kp, | ||
}, nil | ||
} | ||
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type macaroonDischarger struct { | ||
ofgaClient *openfga.OFGAClient | ||
bakery *bakery.Bakery | ||
kp bakery.KeyPair | ||
} | ||
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// thirdPartyCaveatCheckerFunction returns a function that | ||
// checks third party caveats addressed to this service. | ||
// Caveat format is: | ||
// | ||
// is-<relation name> <user tag> <resource tag> | ||
// | ||
// Examples of caveats are: | ||
// | ||
// is-reader <user tag> <offer tag containing uuid> | ||
// is-consumer <user tag> <offer tag containing uuid> | ||
// is-administrator <user tag> <offer tag containing uuid> | ||
// is-reader <user tag> <model tag containing uuid> | ||
// is-writer <user tag> <model tag containing uuid> | ||
// is-admininistrator <user tag> <model tag containing uuid> | ||
// is-admininistrator <user tag> <controller tag containing uuid> | ||
// | ||
// The discharged macaroon will contain a time-before first party caveat and | ||
// a declared caveat declaring relation to the required entity in form of: | ||
// | ||
// <relation> <entity tag> | ||
// | ||
// Example: | ||
// 1. if the third party caveat condition is: | ||
// is-reader <user tag> <offer tag containing uuid> | ||
// the declared caveat will contain | ||
// reader <offer tag> | ||
// 2. if the third party caveat condition is: | ||
// is-writer <user tag> <model tag containing uuid> | ||
// the declared caveat will contain | ||
// writer <model tag> | ||
func (md *macaroonDischarger) checkThirdPartyCaveat(ctx context.Context, req *http.Request, cavInfo *bakery.ThirdPartyCaveatInfo, _ *httpbakery.DischargeToken) ([]checkers.Caveat, error) { | ||
caveatTokens := strings.Split(string(cavInfo.Condition), " ") | ||
if len(caveatTokens) != 3 { | ||
zapctx.Error(ctx, "caveat token length incorrect", zap.Int("length", len(caveatTokens))) | ||
return nil, checkers.ErrCaveatNotRecognized | ||
} | ||
relationString := caveatTokens[0] | ||
userTagString := caveatTokens[1] | ||
objectTagString := caveatTokens[2] | ||
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if !strings.HasPrefix(relationString, "is-") { | ||
zapctx.Error(ctx, "caveat token relation string missing prefix") | ||
return nil, checkers.ErrCaveatNotRecognized | ||
} | ||
relationString = strings.TrimPrefix(relationString, "is-") | ||
relation, err := ofganames.ParseRelation(relationString) | ||
if err != nil { | ||
zapctx.Error(ctx, "caveat token relation invalid", zap.Error(err)) | ||
return nil, checkers.ErrCaveatNotRecognized | ||
} | ||
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userTag, err := names.ParseUserTag(userTagString) | ||
if err != nil { | ||
zapctx.Error(ctx, "failed to parse caveat user tag", zap.Error(err)) | ||
return nil, checkers.ErrCaveatNotRecognized | ||
} | ||
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objectTag, err := jimmnames.ParseTag(objectTagString) | ||
if err != nil { | ||
zapctx.Error(ctx, "failed to parse caveat object tag", zap.Error(err)) | ||
return nil, checkers.ErrCaveatNotRecognized | ||
} | ||
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user := openfga.NewUser( | ||
&dbmodel.User{ | ||
Username: userTag.Id(), | ||
}, | ||
md.ofgaClient, | ||
) | ||
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allowed, err := openfga.CheckRelation(ctx, user, objectTag, relation) | ||
if err != nil { | ||
zapctx.Error(ctx, "failed to check request caveat relation", zap.Error(err)) | ||
return nil, errors.E(err) | ||
} | ||
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if allowed { | ||
return []checkers.Caveat{ | ||
checkers.DeclaredCaveat(relationString, objectTagString), | ||
checkers.TimeBeforeCaveat(time.Now().Add(defaultDischargeExpiry)), | ||
}, nil | ||
} | ||
zapctx.Debug(ctx, "macaroon dishcharge denied", zap.String("user", user.Username), zap.String("object", objectTag.Id())) | ||
return nil, httpbakery.ErrPermissionDenied | ||
} |
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