/* * libwebsockets - JSON Web Signature support * * Copyright (C) 2017 Andy Green * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation: * version 2.1 of the License. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, * MA 02110-1301 USA */ #include "core/private.h" /* * JSON Web Signature is defined in RFC7515 * * https://tools.ietf.org/html/rfc7515 * * It's basically a way to wrap some JSON with a JSON "header" describing the * crypto, and a signature, all in a BASE64 wrapper with elided terminating '='. * * The signature stays with the content, it serves a different purpose than eg * a TLS tunnel to transfer it. * * RFC7518 (JSON Web Algorithms) says for the "alg" names * * | HS256 | HMAC using SHA-256 | Required | * | HS384 | HMAC using SHA-384 | Optional | * | HS512 | HMAC using SHA-512 | Optional | * | RS256 | RSASSA-PKCS1-v1_5 using | Recommended | * | RS384 | RSASSA-PKCS1-v1_5 using | Optional | * | | SHA-384 | | * | RS512 | RSASSA-PKCS1-v1_5 using | Optional | * | | SHA-512 | | * | ES256 | ECDSA using P-256 and SHA-256 | Recommended+ | * | ES384 | ECDSA using P-384 and SHA-384 | Optional | * | ES512 | ECDSA using P-521 and SHA-512 | Optional | * * Boulder (FOSS ACME provider) supports RS256, ES256, ES384 and ES512 * currently. The "Recommended+" just means it is recommended but will likely * be "very recommended" soon. * * We support HS256/384/512 for symmetric crypto, but the choice for the * asymmetric crypto isn't as easy to make. * * Normally you'd choose the EC option but these are defined to use the * "NIST curves" (RFC7518 3.4) which are believed to be insecure. * * https://safecurves.cr.yp.to/ * * For that reason we implement RS256/384/512 for asymmetric. */ #if defined(LWS_WITH_SELFTESTS) static const char *test1 = "{\"typ\":\"JWT\",\r\n \"alg\":\"HS256\"}", *test1_enc = "eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9", *test2 = "{\"iss\":\"joe\",\r\n \"exp\":1300819380,\r\n" " \"http://example.com/is_root\":true}", *test2_enc = "eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQ" "ogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ", *key_jwk = "{\"kty\":\"oct\",\r\n" " \"k\":\"AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQ" "Lr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow\"}", *hash_enc = "dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk", /* the key from worked example in RFC7515 A-1, as a JWK */ *rfc7515_rsa_key = "{\"kty\":\"RSA\"," " \"n\":\"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx" "HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs" "D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH" "SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV" "MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8" "NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ\"," "\"e\":\"AQAB\"," "\"d\":\"Eq5xpGnNCivDflJsRQBXHx1hdR1k6Ulwe2JZD50LpXyWPEAeP88vLNO97I" "jlA7_GQ5sLKMgvfTeXZx9SE-7YwVol2NXOoAJe46sui395IW_GO-pWJ1O0" "BkTGoVEn2bKVRUCgu-GjBVaYLU6f3l9kJfFNS3E0QbVdxzubSu3Mkqzjkn" "439X0M_V51gfpRLI9JYanrC4D4qAdGcopV_0ZHHzQlBjudU2QvXt4ehNYT" "CBr6XCLQUShb1juUO1ZdiYoFaFQT5Tw8bGUl_x_jTj3ccPDVZFD9pIuhLh" "BOneufuBiB4cS98l2SR_RQyGWSeWjnczT0QU91p1DhOVRuOopznQ\"," "\"p\":\"4BzEEOtIpmVdVEZNCqS7baC4crd0pqnRH_5IB3jw3bcxGn6QLvnEtfdUdi" "YrqBdss1l58BQ3KhooKeQTa9AB0Hw_Py5PJdTJNPY8cQn7ouZ2KKDcmnPG" "BY5t7yLc1QlQ5xHdwW1VhvKn-nXqhJTBgIPgtldC-KDV5z-y2XDwGUc\"," "\"q\":\"uQPEfgmVtjL0Uyyx88GZFF1fOunH3-7cepKmtH4pxhtCoHqpWmT8YAmZxa" "ewHgHAjLYsp1ZSe7zFYHj7C6ul7TjeLQeZD_YwD66t62wDmpe_HlB-TnBA" "-njbglfIsRLtXlnDzQkv5dTltRJ11BKBBypeeF6689rjcJIDEz9RWdc\"," "\"dp\":\"BwKfV3Akq5_MFZDFZCnW-wzl-CCo83WoZvnLQwCTeDv8uzluRSnm71I3Q" "CLdhrqE2e9YkxvuxdBfpT_PI7Yz-FOKnu1R6HsJeDCjn12Sk3vmAktV2zb" "34MCdy7cpdTh_YVr7tss2u6vneTwrA86rZtu5Mbr1C1XsmvkxHQAdYo0\"," "\"dq\":\"h_96-mK1R_7glhsum81dZxjTnYynPbZpHziZjeeHcXYsXaaMwkOlODsWa" "7I9xXDoRwbKgB719rrmI2oKr6N3Do9U0ajaHF-NKJnwgjMd2w9cjz3_-ky" "NlxAr2v4IKhGNpmM5iIgOS1VZnOZ68m6_pbLBSp3nssTdlqvd0tIiTHU\"," "\"qi\":\"IYd7DHOhrWvxkwPQsRM2tOgrjbcrfvtQJipd-DlcxyVuuM9sQLdgjVk2o" "y26F0EmpScGLq2MowX7fhd_QJQ3ydy5cY7YIBi87w93IKLEdfnbJtoOPLU" "W0ITrJReOgo1cq9SbsxYawBgfp_gh6A5603k2-ZQwVK0JKSHuLFkuQ3U\"" "}", *rfc7515_rsa_a1 = /* the signed worked example in RFC7515 A-1 */ "eyJhbGciOiJSUzI1NiJ9" ".eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt" "cGxlLmNvbS9pc19yb290Ijp0cnVlfQ" ".cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7" "AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4" "BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K" "0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv" "hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB" "p0igcN_IoypGlUPQGe77Rw"; #endif LWS_VISIBLE int lws_jws_base64_enc(const char *in, size_t in_len, char *out, size_t out_max) { int n; n = lws_b64_encode_string_url(in, in_len, out, out_max - 1); if (n < 0) return n; /* too large for output buffer */ /* trim the terminal = */ while (n && out[n - 1] == '=') n--; out[n] = '\0'; return n; } LWS_VISIBLE int lws_jws_encode_section(const char *in, size_t in_len, int first, char **p, char *end) { int n, len = (end - *p) - 1; char *p_entry = *p; if (len < 3) return -1; if (!first) *(*p)++ = '.'; n = lws_jws_base64_enc(in, in_len, *p, len - 1); if (n < 0) return -1; *p += n; return (*p) - p_entry; } static int lws_jws_find_sig(const char *in, size_t len) { const char *p = in + len - 1; while (len--) if (*p == '.') return (p + 1) - in; else p--; lwsl_notice("%s failed\n", __func__); return -1; } static const char * const jhdr_tok[] = { "typ", "alg", }; enum enum_jhdr_tok { JHP_TYP, JHP_ALG }; struct cb_hdr_s { enum lws_genhash_types hash_type; enum lws_genhmac_types hmac_type; char alg[10]; int is_rsa:1; }; static signed char cb_hdr(struct lejp_ctx *ctx, char reason) { struct cb_hdr_s *s = (struct cb_hdr_s *)ctx->user; if (!(reason & LEJP_FLAG_CB_IS_VALUE) || !ctx->path_match) return 0; switch (ctx->path_match - 1) { case JHP_TYP: /* it is optional */ if (strcmp(ctx->buf, "JWT")) return -1; break; case JHP_ALG: lws_strncpy(s->alg, ctx->buf, sizeof(s->alg)); if (!strcmp(ctx->buf, "HS256")) { s->hmac_type = LWS_GENHMAC_TYPE_SHA256; break; } if (!strcmp(ctx->buf, "HS384")) { s->hmac_type = LWS_GENHMAC_TYPE_SHA384; break; } if (!strcmp(ctx->buf, "HS512")) { s->hmac_type = LWS_GENHMAC_TYPE_SHA512; break; } if (!strcmp(ctx->buf, "RS256")) { s->hash_type = LWS_GENHASH_TYPE_SHA256; s->is_rsa = 1; break; } if (!strcmp(ctx->buf, "RS384")) { s->hash_type = LWS_GENHASH_TYPE_SHA384; s->is_rsa = 1; break; } if (!strcmp(ctx->buf, "RS512")) { s->hash_type = LWS_GENHASH_TYPE_SHA512; s->is_rsa = 1; break; } return -1; } return 0; } LWS_VISIBLE int lws_jws_confirm_sig(const char *in, size_t len, struct lws_jwk *jwk) { int sig_pos = lws_jws_find_sig(in, len), pos = 0, n, m, h_len; uint8_t digest[LWS_GENHASH_LARGEST]; struct lws_genhash_ctx hash_ctx; struct lws_genrsa_ctx rsactx; struct lws_genhmac_ctx ctx; struct cb_hdr_s args; struct lejp_ctx jctx; char buf[2048]; /* 1) there has to be a signature */ if (sig_pos < 0) return -1; /* 2) find length of first, hdr, block */ while (in[pos] != '.' && pos < (int)len) pos++; if (pos == (int)len) return -1; /* 3) Decode the header block */ n = lws_b64_decode_string_len(in, pos, buf, sizeof(buf) - 1); if (n < 0) return -1; /* 4) Require either: * typ: JWT (if present) and alg: HS256/384/512 * typ: JWT (if present) and alg: RS256/384/512 */ args.alg[0] = '\0'; args.is_rsa = 0; lejp_construct(&jctx, cb_hdr, &args, jhdr_tok, ARRAY_SIZE(jhdr_tok)); m = (int)(signed char)lejp_parse(&jctx, (uint8_t *)buf, n); lejp_destruct(&jctx); if (m < 0) { lwsl_notice("parse got %d: alg %s\n", m, args.alg); return -1; } /* 5) decode the B64URL signature part into buf / m */ m = lws_b64_decode_string_len(in + sig_pos, len - sig_pos, buf, sizeof(buf) - 1); if (args.is_rsa) { /* RSASSA-PKCS1-v1_5 using SHA-256/384/512 */ /* 6(RSA): compute the hash of the payload into "digest" */ if (lws_genhash_init(&hash_ctx, args.hash_type)) return -1; if (lws_genhash_update(&hash_ctx, (uint8_t *)in, sig_pos - 1)) { lws_genhash_destroy(&hash_ctx, NULL); return -1; } if (lws_genhash_destroy(&hash_ctx, digest)) return -1; h_len = lws_genhash_size(args.hash_type); if (lws_genrsa_create(&rsactx, &jwk->el)) { lwsl_notice("%s: lws_genrsa_public_decrypt_create\n", __func__); return -1; } n = lws_genrsa_public_verify(&rsactx, digest, args.hash_type, (uint8_t *)buf, m); lws_genrsa_destroy(&rsactx); if (n < 0) { lwsl_notice("decrypt fail\n"); return -1; } return 0; } /* SHA256/384/512 HMAC */ h_len = lws_genhmac_size(args.hmac_type); if (m < 0 || m != h_len) return -1; /* 6) compute HMAC over payload */ if (lws_genhmac_init(&ctx, args.hmac_type, jwk->el.e[JWK_KEY_E].buf, jwk->el.e[JWK_KEY_E].len)) return -1; if (lws_genhmac_update(&ctx, (uint8_t *)in, sig_pos - 1)) { lws_genhmac_destroy(&ctx, NULL); return -1; } if (lws_genhmac_destroy(&ctx, digest)) return -1; /* 7) Compare the computed and decoded hashes */ if (memcmp(digest, buf, h_len)) { lwsl_notice("digest mismatch\n"); return -1; } return 0; } LWS_VISIBLE int lws_jws_sign_from_b64(const char *b64_hdr, size_t hdr_len, const char *b64_pay, size_t pay_len, char *b64_sig, size_t sig_len, enum lws_genhash_types hash_type, struct lws_jwk *jwk) { uint8_t digest[LWS_GENHASH_LARGEST]; struct lws_genhash_ctx hash_ctx; struct lws_genrsa_ctx rsactx; uint8_t *buf; int n; if (lws_genhash_init(&hash_ctx, hash_type)) return -1; if (b64_hdr) { if (lws_genhash_update(&hash_ctx, (uint8_t *)b64_hdr, hdr_len)) goto hash_fail; if (lws_genhash_update(&hash_ctx, (uint8_t *)".", 1)) goto hash_fail; } if (lws_genhash_update(&hash_ctx, (uint8_t *)b64_pay, pay_len)) goto hash_fail; if (lws_genhash_destroy(&hash_ctx, digest)) return -1; if (!strcmp(jwk->keytype, "RSA")) { if (lws_genrsa_create(&rsactx, &jwk->el)) { lwsl_notice("%s: lws_genrsa_public_decrypt_create\n", __func__); return -1; } n = jwk->el.e[JWK_KEY_N].len; buf = lws_malloc(n, "jws sign"); if (!buf) return -1; n = lws_genrsa_public_sign(&rsactx, digest, hash_type, buf, n); lws_genrsa_destroy(&rsactx); if (n < 0) { lws_free(buf); return -1; } n = lws_jws_base64_enc((char *)buf, n, b64_sig, sig_len); lws_free(buf); return n; } if (!strcmp(jwk->keytype, "oct")) return lws_jws_base64_enc((char *)digest, lws_genhash_size(hash_type), b64_sig, sig_len); /* unknown key type */ return -1; hash_fail: lws_genhash_destroy(&hash_ctx, NULL); return -1; } LWS_VISIBLE int lws_jws_create_packet(struct lws_jwk *jwk, const char *payload, size_t len, const char *nonce, char *out, size_t out_len) { char *buf, *start, *p, *end, *p1, *end1, *b64_hdr, *b64_pay; int n, b64_hdr_len, b64_pay_len; /* * This buffer is local to the function, the actual output * is prepared into vhd->buf. Only the plaintext protected header * (which contains the public key, 512 bytes for 4096b) goes in * here temporarily. */ n = LWS_PRE + 2048; buf = malloc(n); if (!buf) { lwsl_notice("%s: malloc %d failed\n", __func__, n); return -1; } p = start = buf + LWS_PRE; end = buf + n - LWS_PRE - 1; /* * temporary JWS protected header plaintext */ p += lws_snprintf(p, end - p, "{\"alg\":\"RS256\",\"jwk\":"); n = lws_jwk_export(jwk, 0, p, end - p); if (n < 0) { lwsl_notice("failed to export jwk\n"); goto bail; } p += n; p += lws_snprintf(p, end - p, ",\"nonce\":\"%s\"}", nonce); /* * prepare the signed outer JSON with all the parts in */ p1 = out; end1 = out + out_len - 1; p1 += lws_snprintf(p1, end1 - p1, "{\"protected\":\""); b64_hdr = p1; n = lws_jws_base64_enc(start, p - start, p1, end1 - p1); if (n < 0) { lwsl_notice("%s: failed to encode protected\n", __func__); goto bail; } b64_hdr_len = n; p1 += n; p1 += lws_snprintf(p1, end1 - p1, "\",\"payload\":\""); b64_pay = p1; n = lws_jws_base64_enc(payload, len, p1, end1 - p1); if (n < 0) { lwsl_notice("%s: failed to encode payload\n", __func__); goto bail; } b64_pay_len = n; p1 += n; p1 += lws_snprintf(p1, end1 - p1, "\",\"signature\":\""); /* * taking the b64 protected header and the b64 payload, sign them * and place the signature into the packet */ n = lws_jws_sign_from_b64(b64_hdr, b64_hdr_len, b64_pay, b64_pay_len, p1, end1 - p1, LWS_GENHASH_TYPE_SHA256, jwk); if (n < 0) { lwsl_notice("sig gen failed\n"); goto bail; } p1 += n; p1 += lws_snprintf(p1, end1 - p1, "\"}"); free(buf); return p1 - out; bail: free(buf); return -1; } #if defined(LWS_WITH_SELFTESTS) /* * These are the inputs and outputs from the worked example in RFC7515 * Appendix A.1. * * 1) has a fixed header + payload, and a fixed SHA256 HMAC key, and must give * a fixed BASE64URL result. * * 2) has a fixed header + payload and is signed with a key given in JWK format */ int lws_jws_selftest(void) { struct lws_genhmac_ctx ctx; struct lws_jwk jwk; char buf[2048], *p = buf, *end = buf + sizeof(buf) - 1, *enc_ptr, *p1; uint8_t digest[LWS_GENHASH_LARGEST]; int n; /* Test 1: SHA256 on RFC7515 worked example */ /* 1.1: decode the JWK oct key */ if (lws_jwk_import(&jwk, key_jwk, strlen(key_jwk)) < 0) { lwsl_notice("Failed to decode JWK test key\n"); return -1; } /* 1.2: create JWS known hdr + known payload */ n = lws_jws_encode_section(test1, strlen(test1), 1, &p, end); if (n < 0) goto bail; if (strcmp(buf, test1_enc)) goto bail; enc_ptr = p + 1; /* + 1 skips the . */ n = lws_jws_encode_section(test2, strlen(test2), 0, &p, end); if (n < 0) goto bail; if (strcmp(enc_ptr, test2_enc)) goto bail; /* 1.3: use HMAC SHA-256 with known key on the hdr . payload */ if (lws_genhmac_init(&ctx, LWS_GENHMAC_TYPE_SHA256, jwk.el.e[JWK_KEY_E].buf, jwk.el.e[JWK_KEY_E].len)) goto bail; if (lws_genhmac_update(&ctx, (uint8_t *)buf, p - buf)) goto bail_destroy_hmac; lws_genhmac_destroy(&ctx, digest); /* 1.4: append a base64 encode of the computed HMAC digest */ enc_ptr = p + 1; /* + 1 skips the . */ n = lws_jws_encode_section((const char *)digest, 32, 0, &p, end); if (n < 0) goto bail; if (strcmp(enc_ptr, hash_enc)) /* check against known B64URL hash */ goto bail; /* 1.5: Check we can agree the signature matches the payload */ if (lws_jws_confirm_sig(buf, p - buf, &jwk) < 0) { lwsl_notice("confirm sig failed\n"); goto bail; } lws_jwk_destroy(&jwk); /* finished with the key from the first test */ /* Test 2: RSA256 on RFC7515 worked example */ /* 2.1: turn the known JWK key for the RSA test into a lws_jwk */ if (lws_jwk_import(&jwk, rfc7515_rsa_key, strlen(rfc7515_rsa_key))) { lwsl_notice("Failed to read JWK key\n"); goto bail2; } /* 2.2: check the signature on the test packet from RFC7515 A-1 */ if (lws_jws_confirm_sig(rfc7515_rsa_a1, strlen(rfc7515_rsa_a1), &jwk) < 0) { lwsl_notice("confirm rsa sig failed\n"); goto bail; } /* 2.3: generate our own signature for a copy of the test packet */ memcpy(buf, rfc7515_rsa_a1, strlen(rfc7515_rsa_a1)); /* set p to second . */ p = strchr(buf + 1, '.'); p1 = strchr(p + 1, '.'); n = lws_jws_sign_from_b64(buf, p - buf, p + 1, p1 - (p + 1), p1 + 1, sizeof(buf) - (p1 - buf) - 1, LWS_GENHASH_TYPE_SHA256, &jwk); if (n < 0) goto bail; puts(buf); /* 2.4: confirm our signature can be verified */ if (lws_jws_confirm_sig(buf, (p1 + 1 + n) - buf, &jwk) < 0) { lwsl_notice("confirm rsa sig 2 failed\n"); goto bail; } lws_jwk_destroy(&jwk); /* end */ lwsl_notice("%s: selftest OK\n", __func__); return 0; bail_destroy_hmac: lws_genhmac_destroy(&ctx, NULL); bail: lws_jwk_destroy(&jwk); bail2: lwsl_err("%s: selftest failed ++++++++++++++++++++\n", __func__); return 1; } #endif