diff options
Diffstat (limited to 'src/core/security/jwt_verifier.c')
| -rw-r--r-- | src/core/security/jwt_verifier.c | 830 |
1 files changed, 830 insertions, 0 deletions
diff --git a/src/core/security/jwt_verifier.c b/src/core/security/jwt_verifier.c new file mode 100644 index 0000000000..01007a1a84 --- /dev/null +++ b/src/core/security/jwt_verifier.c @@ -0,0 +1,830 @@ +/* + * + * Copyright 2015, Google Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimser. + * * Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following disclaimser + * in the documentation and/or other materials provided with the + * distribution. + * * Neither the name of Google Inc. nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + */ + +#include "src/core/security/jwt_verifier.h" + +#include <string.h> + +#include "src/core/httpcli/httpcli.h" +#include "src/core/security/base64.h" + +#include <grpc/support/alloc.h> +#include <grpc/support/log.h> +#include <grpc/support/string_util.h> +#include <grpc/support/sync.h> +#include <openssl/pem.h> + +/* --- Utils. --- */ + +const char *grpc_jwt_verifier_status_to_string( + grpc_jwt_verifier_status status) { + switch (status) { + case GRPC_JWT_VERIFIER_OK: + return "OK"; + case GRPC_JWT_VERIFIER_BAD_SIGNATURE: + return "BAD_SIGNATURE"; + case GRPC_JWT_VERIFIER_BAD_FORMAT: + return "BAD_FORMAT"; + case GRPC_JWT_VERIFIER_BAD_AUDIENCE: + return "BAD_AUDIENCE"; + case GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR: + return "KEY_RETRIEVAL_ERROR"; + case GRPC_JWT_VERIFIER_TIME_CONSTRAINT_FAILURE: + return "TIME_CONSTRAINT_FAILURE"; + case GRPC_JWT_VERIFIER_GENERIC_ERROR: + return "GENERIC_ERROR"; + default: + return "UNKNOWN"; + } +} + +static const EVP_MD *evp_md_from_alg(const char *alg) { + if (strcmp(alg, "RS256") == 0) { + return EVP_sha256(); + } else if (strcmp(alg, "RS384") == 0) { + return EVP_sha384(); + } else if (strcmp(alg, "RS512") == 0) { + return EVP_sha512(); + } else { + return NULL; + } +} + +static grpc_json *parse_json_part_from_jwt(const char *str, size_t len, + gpr_slice *buffer) { + grpc_json *json; + + *buffer = grpc_base64_decode_with_len(str, len, 1); + if (GPR_SLICE_IS_EMPTY(*buffer)) { + gpr_log(GPR_ERROR, "Invalid base64."); + return NULL; + } + json = grpc_json_parse_string_with_len((char *)GPR_SLICE_START_PTR(*buffer), + GPR_SLICE_LENGTH(*buffer)); + if (json == NULL) { + gpr_slice_unref(*buffer); + gpr_log(GPR_ERROR, "JSON parsing error."); + } + return json; +} + +static const char *validate_string_field(const grpc_json *json, + const char *key) { + if (json->type != GRPC_JSON_STRING) { + gpr_log(GPR_ERROR, "Invalid %s field [%s]", key, json->value); + return NULL; + } + return json->value; +} + +static gpr_timespec validate_time_field(const grpc_json *json, + const char *key) { + gpr_timespec result = gpr_time_0; + if (json->type != GRPC_JSON_NUMBER) { + gpr_log(GPR_ERROR, "Invalid %s field [%s]", key, json->value); + return result; + } + result.tv_sec = strtol(json->value, NULL, 10); + return result; +} + +/* --- JOSE header. see http://tools.ietf.org/html/rfc7515#section-4 --- */ + +typedef struct { + const char *alg; + const char *kid; + const char *typ; + /* TODO(jboeuf): Add others as needed (jku, jwk, x5u, x5c and so on...). */ + gpr_slice buffer; +} jose_header; + +static void jose_header_destroy(jose_header *h) { + gpr_slice_unref(h->buffer); + gpr_free(h); +} + +/* Takes ownership of json and buffer. */ +static jose_header *jose_header_from_json(grpc_json *json, gpr_slice buffer) { + grpc_json *cur; + jose_header *h = gpr_malloc(sizeof(jose_header)); + memset(h, 0, sizeof(jose_header)); + h->buffer = buffer; + for (cur = json->child; cur != NULL; cur = cur->next) { + if (strcmp(cur->key, "alg") == 0) { + /* We only support RSA-1.5 signatures for now. + Beware of this if we add HMAC support: + https://auth0.com/blog/2015/03/31/critical-vulnerabilities-in-json-web-token-libraries/ + */ + if (cur->type != GRPC_JSON_STRING || strncmp(cur->value, "RS", 2) || + evp_md_from_alg(cur->value) == NULL) { + gpr_log(GPR_ERROR, "Invalid alg field [%s]", cur->value); + goto error; + } + h->alg = cur->value; + } else if (strcmp(cur->key, "typ") == 0) { + h->typ = validate_string_field(cur, "typ"); + if (h->typ == NULL) goto error; + } else if (strcmp(cur->key, "kid") == 0) { + h->kid = validate_string_field(cur, "kid"); + if (h->kid == NULL) goto error; + } + } + if (h->alg == NULL) { + gpr_log(GPR_ERROR, "Missing alg field."); + goto error; + } + grpc_json_destroy(json); + h->buffer = buffer; + return h; + +error: + grpc_json_destroy(json); + jose_header_destroy(h); + return NULL; +} + +/* --- JWT claims. see http://tools.ietf.org/html/rfc7519#section-4.1 */ + +struct grpc_jwt_claims { + /* Well known properties already parsed. */ + const char *sub; + const char *iss; + const char *aud; + const char *jti; + gpr_timespec iat; + gpr_timespec exp; + gpr_timespec nbf; + + grpc_json *json; + gpr_slice buffer; +}; + + +void grpc_jwt_claims_destroy(grpc_jwt_claims *claims) { + grpc_json_destroy(claims->json); + gpr_slice_unref(claims->buffer); + gpr_free(claims); +} + +const grpc_json *grpc_jwt_claims_json(const grpc_jwt_claims *claims) { + if (claims == NULL) return NULL; + return claims->json; +} + +const char *grpc_jwt_claims_subject(const grpc_jwt_claims *claims) { + if (claims == NULL) return NULL; + return claims->sub; +} + +const char *grpc_jwt_claims_issuer(const grpc_jwt_claims *claims) { + if (claims == NULL) return NULL; + return claims->iss; +} + +const char *grpc_jwt_claims_id(const grpc_jwt_claims *claims) { + if (claims == NULL) return NULL; + return claims->jti; +} + +const char *grpc_jwt_claims_audience(const grpc_jwt_claims *claims) { + if (claims == NULL) return NULL; + return claims->aud; +} + +gpr_timespec grpc_jwt_claims_issued_at(const grpc_jwt_claims *claims) { + if (claims == NULL) return gpr_inf_past; + return claims->iat; +} + +gpr_timespec grpc_jwt_claims_expires_at(const grpc_jwt_claims *claims) { + if (claims == NULL) return gpr_inf_future; + return claims->exp; +} + +gpr_timespec grpc_jwt_claims_not_before(const grpc_jwt_claims *claims) { + if (claims == NULL) return gpr_inf_past; + return claims->nbf; +} + +/* Takes ownership of json and buffer even in case of failure. */ +grpc_jwt_claims *grpc_jwt_claims_from_json(grpc_json *json, gpr_slice buffer) { + grpc_json *cur; + grpc_jwt_claims *claims = gpr_malloc(sizeof(grpc_jwt_claims)); + memset(claims, 0, sizeof(grpc_jwt_claims)); + claims->json = json; + claims->buffer = buffer; + claims->iat = gpr_inf_past; + claims->nbf = gpr_inf_past; + claims->exp = gpr_inf_future; + + /* Per the spec, all fields are optional. */ + for (cur = json->child; cur != NULL; cur = cur->next) { + if (strcmp(cur->key, "sub") == 0) { + claims->sub = validate_string_field(cur, "sub"); + if (claims->sub == NULL) goto error; + } else if (strcmp(cur->key, "iss") == 0) { + claims->iss = validate_string_field(cur, "iss"); + if (claims->iss == NULL) goto error; + } else if (strcmp(cur->key, "aud") == 0) { + claims->aud = validate_string_field(cur, "aud"); + if (claims->aud == NULL) goto error; + } else if (strcmp(cur->key, "jti") == 0) { + claims->jti = validate_string_field(cur, "jti"); + if (claims->jti == NULL) goto error; + } else if (strcmp(cur->key, "iat") == 0) { + claims->iat = validate_time_field(cur, "iat"); + if (gpr_time_cmp(claims->iat, gpr_time_0) == 0) goto error; + } else if (strcmp(cur->key, "exp") == 0) { + claims->exp = validate_time_field(cur, "exp"); + if (gpr_time_cmp(claims->exp, gpr_time_0) == 0) goto error; + } else if (strcmp(cur->key, "nbf") == 0) { + claims->nbf = validate_time_field(cur, "nbf"); + if (gpr_time_cmp(claims->nbf, gpr_time_0) == 0) goto error; + } + } + return claims; + +error: + grpc_jwt_claims_destroy(claims); + return NULL; +} + +grpc_jwt_verifier_status grpc_jwt_claims_check(const grpc_jwt_claims *claims, + const char *audience) { + gpr_timespec skewed_now; + int audience_ok; + + GPR_ASSERT(claims != NULL); + + skewed_now = gpr_time_add(gpr_now(), grpc_jwt_verifier_clock_skew); + if (gpr_time_cmp(skewed_now, claims->nbf) < 0) { + gpr_log(GPR_ERROR, "JWT is not valid yet."); + return GRPC_JWT_VERIFIER_TIME_CONSTRAINT_FAILURE; + } + skewed_now = gpr_time_sub(gpr_now(), grpc_jwt_verifier_clock_skew); + if (gpr_time_cmp(skewed_now, claims->exp) > 0) { + gpr_log(GPR_ERROR, "JWT is expired."); + return GRPC_JWT_VERIFIER_TIME_CONSTRAINT_FAILURE; + } + + if (audience == NULL) { + audience_ok = claims->aud == NULL; + } else { + audience_ok = claims->aud != NULL && strcmp(audience, claims->aud) == 0; + } + if (!audience_ok) { + gpr_log(GPR_ERROR, "Audience mismatch: expected %s and found %s.", + audience == NULL ? "NULL" : audience, + claims->aud == NULL ? "NULL" : claims->aud); + return GRPC_JWT_VERIFIER_BAD_AUDIENCE; + } + return GRPC_JWT_VERIFIER_OK; +} + +/* --- verifier_cb_ctx object. --- */ + +typedef struct { + grpc_jwt_verifier *verifier; + grpc_pollset *pollset; + jose_header *header; + grpc_jwt_claims *claims; + char *audience; + gpr_slice signature; + gpr_slice signed_data; + void *user_data; + grpc_jwt_verification_done_cb user_cb; +} verifier_cb_ctx; + +/* Takes ownership of the header, claims and signature. */ +static verifier_cb_ctx *verifier_cb_ctx_create( + grpc_jwt_verifier *verifier, grpc_pollset *pollset, + jose_header * header, grpc_jwt_claims *claims, const char *audience, + gpr_slice signature, const char *signed_jwt, size_t signed_jwt_len, + void *user_data, grpc_jwt_verification_done_cb cb) { + verifier_cb_ctx *ctx = gpr_malloc(sizeof(verifier_cb_ctx)); + memset(ctx, 0, sizeof(verifier_cb_ctx)); + ctx->verifier = verifier; + ctx->pollset = pollset; + ctx->header = header; + ctx->audience = gpr_strdup(audience); + ctx->claims = claims; + ctx->signature = signature; + ctx->signed_data = gpr_slice_from_copied_buffer(signed_jwt, signed_jwt_len); + ctx->user_data = user_data; + ctx->user_cb = cb; + return ctx; +} + +void verifier_cb_ctx_destroy(verifier_cb_ctx *ctx) { + if (ctx->audience != NULL) gpr_free(ctx->audience); + if (ctx->claims != NULL) grpc_jwt_claims_destroy(ctx->claims); + gpr_slice_unref(ctx->signature); + gpr_slice_unref(ctx->signed_data); + jose_header_destroy(ctx->header); + /* TODO: see what to do with claims... */ + gpr_free(ctx); +} + +/* --- grpc_jwt_verifier object. --- */ + +/* Clock skew defaults to one minute. */ +gpr_timespec grpc_jwt_verifier_clock_skew = {60, 0}; + +/* Max delay defaults to one minute. */ +gpr_timespec grpc_jwt_verifier_max_delay = {60, 0}; + +typedef struct { + char *email_domain; + char *key_url_prefix; +} email_key_mapping; + +struct grpc_jwt_verifier { + email_key_mapping *mappings; + size_t num_mappings; /* Should be very few, linear search ok. */ + size_t allocated_mappings; + grpc_httpcli_context http_ctx; +}; + +static grpc_json *json_from_http(const grpc_httpcli_response *response) { + grpc_json *json = NULL; + + if (response == NULL) { + gpr_log(GPR_ERROR, "HTTP response is NULL."); + return NULL; + } + if (response->status != 200) { + gpr_log(GPR_ERROR, "Call to http server failed with error %d.", + response->status); + return NULL; + } + + json = grpc_json_parse_string_with_len(response->body, response->body_length); + if (json == NULL) { + gpr_log(GPR_ERROR, "Invalid JSON found in response."); + } + return json; +} + +static const grpc_json *find_property_by_name(const grpc_json *json, + const char *name) { + const grpc_json *cur; + for (cur = json->child; cur != NULL; cur = cur->next) { + if (strcmp(cur->key, name) == 0) return cur; + } + return NULL; +} + +static EVP_PKEY *extract_pkey_from_x509(const char *x509_str) { + X509 *x509 = NULL; + EVP_PKEY *result = NULL; + BIO *bio = BIO_new(BIO_s_mem()); + BIO_write(bio, x509_str, strlen(x509_str)); + x509 = PEM_read_bio_X509(bio, NULL, NULL, NULL); + if (x509 == NULL) { + gpr_log(GPR_ERROR, "Unable to parse x509 cert."); + goto end; + } + result = X509_get_pubkey(x509); + if (result == NULL) { + gpr_log(GPR_ERROR, "Cannot find public key in X509 cert."); + } + +end: + BIO_free(bio); + if (x509 != NULL) X509_free(x509); + return result; +} + +static BIGNUM *bignum_from_base64(const char *b64) { + BIGNUM *result = NULL; + gpr_slice bin; + + if (b64 == NULL) return NULL; + bin = grpc_base64_decode(b64, 1); + if (GPR_SLICE_IS_EMPTY(bin)) { + gpr_log(GPR_ERROR, "Invalid base64 for big num."); + return NULL; + } + result = BN_bin2bn(GPR_SLICE_START_PTR(bin), GPR_SLICE_LENGTH(bin), NULL); + gpr_slice_unref(bin); + return result; +} + +static EVP_PKEY *pkey_from_jwk(const grpc_json *json, const char *kty) { + const grpc_json *key_prop; + RSA *rsa = NULL; + EVP_PKEY *result = NULL; + + GPR_ASSERT(kty != NULL && json != NULL); + if (strcmp(kty, "RSA") != 0) { + gpr_log(GPR_ERROR, "Unsupported key type %s.", kty); + goto end; + } + rsa = RSA_new(); + if (rsa == NULL) { + gpr_log(GPR_ERROR, "Could not create rsa key."); + goto end; + } + for (key_prop = json->child; key_prop != NULL; key_prop = key_prop->next) { + if (strcmp(key_prop->key, "n") == 0) { + rsa->n = bignum_from_base64(validate_string_field(key_prop, "n")); + if (rsa->n == NULL) goto end; + } else if (strcmp(key_prop->key, "e") == 0) { + rsa->e = bignum_from_base64(validate_string_field(key_prop, "e")); + if (rsa->e == NULL) goto end; + } + } + if (rsa->e == NULL || rsa->n == NULL) { + gpr_log(GPR_ERROR, "Missing RSA public key field."); + goto end; + } + result = EVP_PKEY_new(); + EVP_PKEY_set1_RSA(result, rsa); /* uprefs rsa. */ + +end: + if (rsa != NULL) RSA_free(rsa); + return result; +} + +static EVP_PKEY *find_verification_key(const grpc_json *json, + const char *header_alg, + const char *header_kid) { + const grpc_json *jkey; + const grpc_json *jwk_keys; + /* Try to parse the json as a JWK set: + https://tools.ietf.org/html/rfc7517#section-5. */ + jwk_keys = find_property_by_name(json, "keys"); + if (jwk_keys == NULL) { + /* Use the google proprietary format which is: + { <kid1>: <x5091>, <kid2>: <x5092>, ... } */ + const grpc_json *cur = find_property_by_name(json, header_kid); + if (cur == NULL) return NULL; + return extract_pkey_from_x509(cur->value); + } + + if (jwk_keys->type != GRPC_JSON_ARRAY) { + gpr_log(GPR_ERROR, + "Unexpected value type of keys property in jwks key set."); + return NULL; + } + /* Key format is specified in: + https://tools.ietf.org/html/rfc7518#section-6. */ + for (jkey = jwk_keys->child; jkey != NULL; jkey = jkey->next) { + grpc_json *key_prop; + const char *alg = NULL; + const char *kid = NULL; + const char *kty = NULL; + + if (jkey->type != GRPC_JSON_OBJECT) continue; + for (key_prop = jkey->child; key_prop != NULL; key_prop = key_prop->next) { + if (strcmp(key_prop->key, "alg") == 0 && + key_prop->type == GRPC_JSON_STRING) { + alg = key_prop->value; + } else if (strcmp(key_prop->key, "kid") == 0 && + key_prop->type == GRPC_JSON_STRING) { + kid = key_prop->value; + } else if (strcmp(key_prop->key, "kty") == 0 && + key_prop->type == GRPC_JSON_STRING) { + kty = key_prop->value; + } + } + if (alg != NULL && kid != NULL && kty != NULL && + strcmp(kid, header_kid) == 0 && strcmp(alg, header_alg) == 0) { + return pkey_from_jwk(jkey, kty); + } + } + gpr_log(GPR_ERROR, + "Could not find matching key in key set for kid=%s and alg=%s", + header_kid, header_alg); + return NULL; +} + +static int verify_jwt_signature(EVP_PKEY *key, const char *alg, + gpr_slice signature, gpr_slice signed_data) { + EVP_MD_CTX *md_ctx = EVP_MD_CTX_create(); + const EVP_MD *md = evp_md_from_alg(alg); + int result = 0; + + GPR_ASSERT(md != NULL); /* Checked before. */ + if (md_ctx == NULL) { + gpr_log(GPR_ERROR, "Could not create EVP_MD_CTX."); + goto end; + } + if (EVP_DigestVerifyInit(md_ctx, NULL, md, NULL, key) != 1) { + gpr_log(GPR_ERROR, "EVP_DigestVerifyInit failed."); + goto end; + } + if (EVP_DigestVerifyUpdate(md_ctx, GPR_SLICE_START_PTR(signed_data), + GPR_SLICE_LENGTH(signed_data)) != 1) { + gpr_log(GPR_ERROR, "EVP_DigestVerifyUpdate failed."); + goto end; + } + if (EVP_DigestVerifyFinal(md_ctx, GPR_SLICE_START_PTR(signature), + GPR_SLICE_LENGTH(signature)) != 1) { + gpr_log(GPR_ERROR, "JWT signature verification failed."); + goto end; + } + result = 1; + +end: + if (md_ctx != NULL) EVP_MD_CTX_destroy(md_ctx); + return result; +} + +static void on_keys_retrieved(void *user_data, + const grpc_httpcli_response *response) { + grpc_json *json = json_from_http(response); + verifier_cb_ctx *ctx = (verifier_cb_ctx *)user_data; + EVP_PKEY *verification_key = NULL; + grpc_jwt_verifier_status status = GRPC_JWT_VERIFIER_GENERIC_ERROR; + grpc_jwt_claims *claims = NULL; + + if (json == NULL) { + status = GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR; + goto end; + } + verification_key = + find_verification_key(json, ctx->header->alg, ctx->header->kid); + if (verification_key == NULL) { + gpr_log(GPR_ERROR, "Could not find verification key with kid %s.", + ctx->header->kid); + status = GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR; + goto end; + } + + if (!verify_jwt_signature(verification_key, ctx->header->alg, ctx->signature, + ctx->signed_data)) { + status = GRPC_JWT_VERIFIER_BAD_SIGNATURE; + goto end; + } + + status = grpc_jwt_claims_check(ctx->claims, ctx->audience); + if (status == GRPC_JWT_VERIFIER_OK) { + /* Pass ownership. */ + claims = ctx->claims; + ctx->claims = NULL; + } + +end: + if (json != NULL) grpc_json_destroy(json); + if (verification_key != NULL) EVP_PKEY_free(verification_key); + ctx->user_cb(ctx->user_data, status, claims); + verifier_cb_ctx_destroy(ctx); +} + +static void on_openid_config_retrieved(void *user_data, + const grpc_httpcli_response *response) { + const grpc_json* cur; + grpc_json *json = json_from_http(response); + verifier_cb_ctx *ctx = (verifier_cb_ctx *)user_data; + grpc_httpcli_request req; + const char *jwks_uri; + + /* TODO(jboeuf): Cache the jwks_uri in order to avoid this hop next time.*/ + if (json == NULL) goto error; + cur = find_property_by_name(json, "jwks_uri"); + if (cur == NULL) { + gpr_log(GPR_ERROR, "Could not find jwks_uri in openid config."); + goto error; + } + jwks_uri = validate_string_field(cur, "jwks_uri"); + if (jwks_uri == NULL) goto error; + if (strstr(jwks_uri, "https://") != jwks_uri) { + gpr_log(GPR_ERROR, "Invalid non https jwks_uri: %s.", jwks_uri); + goto error; + } + jwks_uri += 8; + req.use_ssl = 1; + req.host = gpr_strdup(jwks_uri); + req.path = strchr(jwks_uri, '/'); + if (req.path == NULL) { + req.path = ""; + } else { + *(req.host + (req.path - jwks_uri)) = '\0'; + } + grpc_httpcli_get(&ctx->verifier->http_ctx, ctx->pollset, &req, + gpr_time_add(gpr_now(), grpc_jwt_verifier_max_delay), + on_keys_retrieved, ctx); + grpc_json_destroy(json); + gpr_free(req.host); + return; + +error: + if (json != NULL) grpc_json_destroy(json); + ctx->user_cb(ctx->user_data, GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR, NULL); + verifier_cb_ctx_destroy(ctx); +} + +static email_key_mapping *verifier_get_mapping( + grpc_jwt_verifier *v, const char *email_domain) { + size_t i; + if (v->mappings == NULL) return NULL; + for (i = 0; i < v->num_mappings; i++) { + if (strcmp(email_domain, v->mappings[i].email_domain) == 0) { + return &v->mappings[i]; + } + } + return NULL; +} + +static void verifier_put_mapping(grpc_jwt_verifier *v, const char *email_domain, + const char *key_url_prefix) { + email_key_mapping *mapping = verifier_get_mapping(v, email_domain); + GPR_ASSERT(v->num_mappings < v->allocated_mappings); + if (mapping != NULL) { + gpr_free(mapping->key_url_prefix); + mapping->key_url_prefix = gpr_strdup(key_url_prefix); + return; + } + v->mappings[v->num_mappings].email_domain = gpr_strdup(email_domain); + v->mappings[v->num_mappings].key_url_prefix = gpr_strdup(key_url_prefix); + v->num_mappings++; + GPR_ASSERT(v->num_mappings <= v->allocated_mappings); +} + +/* Takes ownership of ctx. */ +static void retrieve_key_and_verify(verifier_cb_ctx *ctx) { + const char *at_sign; + grpc_httpcli_response_cb http_cb; + char *path_prefix = NULL; + const char *iss; + grpc_httpcli_request req; + memset(&req, 0, sizeof(grpc_httpcli_request)); + req.use_ssl = 1; + + GPR_ASSERT(ctx != NULL && ctx->header != NULL && ctx->claims != NULL); + iss = ctx->claims->iss; + if (ctx->header->kid == NULL) { + gpr_log(GPR_ERROR, "Missing kid in jose header."); + goto error; + } + if (iss == NULL) { + gpr_log(GPR_ERROR, "Missing iss in claims."); + goto error; + } + + /* This code relies on: + https://openid.net/specs/openid-connect-discovery-1_0.html + Nobody seems to implement the account/email/webfinger part 2. of the spec + so we will rely instead on email/url mappings if we detect such an issuer. + Part 4, on the other hand is implemented by both google and salesforce. */ + + /* Very non-sophisticated way to detect an email address. Should be good + enough for now... */ + at_sign = strchr(iss, '@'); + if (at_sign != NULL) { + email_key_mapping *mapping; + const char *email_domain = at_sign + 1; + GPR_ASSERT(ctx->verifier != NULL); + mapping = verifier_get_mapping(ctx->verifier, email_domain); + if (mapping == NULL) { + gpr_log(GPR_ERROR, "Missing mapping for issuer email."); + goto error; + } + req.host = gpr_strdup(mapping->key_url_prefix); + path_prefix = strchr(req.host, '/'); + if (path_prefix == NULL) { + gpr_asprintf(&req.path, "/%s", iss); + } else { + *(path_prefix++) = '\0'; + gpr_asprintf(&req.path, "/%s/%s", path_prefix, iss); + } + http_cb = on_keys_retrieved; + } else { + req.host = gpr_strdup(strstr(iss, "https://") == iss ? iss + 8 : iss); + path_prefix = strchr(req.host, '/'); + if (path_prefix == NULL) { + req.path = gpr_strdup(GRPC_OPENID_CONFIG_URL_SUFFIX); + } else { + *(path_prefix++) = 0; + gpr_asprintf(&req.path, "/%s%s", path_prefix, + GRPC_OPENID_CONFIG_URL_SUFFIX); + } + http_cb = on_openid_config_retrieved; + } + + grpc_httpcli_get(&ctx->verifier->http_ctx, ctx->pollset, &req, + gpr_time_add(gpr_now(), grpc_jwt_verifier_max_delay), + http_cb, ctx); + gpr_free(req.host); + gpr_free(req.path); + return; + +error: + ctx->user_cb(ctx->user_data, GRPC_JWT_VERIFIER_KEY_RETRIEVAL_ERROR, NULL); + verifier_cb_ctx_destroy(ctx); +} + +void grpc_jwt_verifier_verify(grpc_jwt_verifier *verifier, + grpc_pollset *pollset, const char *jwt, + const char *audience, + grpc_jwt_verification_done_cb cb, + void *user_data) { + const char *dot = NULL; + grpc_json *json; + jose_header *header = NULL; + grpc_jwt_claims *claims = NULL; + gpr_slice header_buffer; + gpr_slice claims_buffer; + gpr_slice signature; + size_t signed_jwt_len; + const char *cur = jwt; + + GPR_ASSERT(verifier != NULL && jwt != NULL && audience != NULL && cb != NULL); + dot = strchr(cur, '.'); + if (dot == NULL) goto error; + json = parse_json_part_from_jwt(cur, dot - cur, &header_buffer); + if (json == NULL) goto error; + header = jose_header_from_json(json, header_buffer); + if (header == NULL) goto error; + + cur = dot + 1; + dot = strchr(cur, '.'); + if (dot == NULL) goto error; + json = parse_json_part_from_jwt(cur, dot - cur, &claims_buffer); + if (json == NULL) goto error; + claims = grpc_jwt_claims_from_json(json, claims_buffer); + if (claims == NULL) goto error; + + signed_jwt_len = (size_t)(dot - jwt); + cur = dot + 1; + signature = grpc_base64_decode(cur, 1); + if (GPR_SLICE_IS_EMPTY(signature)) goto error; + retrieve_key_and_verify( + verifier_cb_ctx_create(verifier, pollset, header, claims, audience, + signature, jwt, signed_jwt_len, user_data, cb)); + return; + +error: + if (header != NULL) jose_header_destroy(header); + if (claims != NULL) grpc_jwt_claims_destroy(claims); + cb(user_data, GRPC_JWT_VERIFIER_BAD_FORMAT, NULL); +} + +grpc_jwt_verifier *grpc_jwt_verifier_create( + const grpc_jwt_verifier_email_domain_key_url_mapping *mappings, + size_t num_mappings) { + grpc_jwt_verifier *v = gpr_malloc(sizeof(grpc_jwt_verifier)); + memset(v, 0, sizeof(grpc_jwt_verifier)); + grpc_httpcli_context_init(&v->http_ctx); + + /* We know at least of one mapping. */ + v->allocated_mappings = 1 + num_mappings; + v->mappings = gpr_malloc(v->allocated_mappings * sizeof(email_key_mapping)); + verifier_put_mapping(v, GRPC_GOOGLE_SERVICE_ACCOUNTS_EMAIL_DOMAIN, + GRPC_GOOGLE_SERVICE_ACCOUNTS_KEY_URL_PREFIX); + /* User-Provided mappings. */ + if (mappings != NULL) { + size_t i; + for (i = 0; i < num_mappings; i++) { + verifier_put_mapping(v, mappings[i].email_domain, + mappings[i].key_url_prefix); + } + } + return v; +} + +void grpc_jwt_verifier_destroy(grpc_jwt_verifier *v) { + size_t i; + if (v == NULL) return; + grpc_httpcli_context_destroy(&v->http_ctx); + if (v->mappings != NULL) { + for (i = 0; i < v->num_mappings; i++) { + gpr_free(v->mappings[i].email_domain); + gpr_free(v->mappings[i].key_url_prefix); + } + gpr_free(v->mappings); + } + gpr_free(v); +} + |