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Diffstat (limited to '')
| -rw-r--r-- | sk-usbhid.c | 1261 |
1 files changed, 1261 insertions, 0 deletions
diff --git a/sk-usbhid.c b/sk-usbhid.c new file mode 100644 index 0000000..007c596 --- /dev/null +++ b/sk-usbhid.c @@ -0,0 +1,1261 @@ +/* $OpenBSD: sk-usbhid.c,v 1.26 2020/09/09 03:08:01 djm Exp $ */ +/* + * Copyright (c) 2019 Markus Friedl + * Copyright (c) 2020 Pedro Martelletto + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +#include "includes.h" + +#ifdef ENABLE_SK_INTERNAL + +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <stdio.h> +#include <stddef.h> +#include <stdarg.h> +#ifdef HAVE_SHA2_H +#include <sha2.h> +#endif + +#ifdef WITH_OPENSSL +#include <openssl/opensslv.h> +#include <openssl/crypto.h> +#include <openssl/bn.h> +#include <openssl/ec.h> +#include <openssl/ecdsa.h> +#include <openssl/evp.h> +#endif /* WITH_OPENSSL */ + +#include <fido.h> +#include <fido/credman.h> + +/* backwards compat for libfido2 */ +#ifndef HAVE_FIDO_CRED_PROT +#define fido_cred_prot(x) (0) +#endif +#ifndef HAVE_FIDO_CRED_SET_PROT +#define fido_cred_set_prot(x, y) (FIDO_ERR_UNSUPPORTED_OPTION) +#endif +#ifndef HAVE_FIDO_DEV_SUPPORTS_CRED_PROT +#define fido_dev_supports_cred_prot(x) (0) +#endif +#ifndef HAVE_FIDO_DEV_GET_TOUCH_BEGIN +#define fido_dev_get_touch_begin(x) (FIDO_ERR_UNSUPPORTED_OPTION) +#endif +#ifndef HAVE_FIDO_DEV_GET_TOUCH_STATUS +#define fido_dev_get_touch_status(x, y, z) (FIDO_ERR_UNSUPPORTED_OPTION) +#endif +#ifndef FIDO_CRED_PROT_UV_REQUIRED +#define FIDO_CRED_PROT_UV_REQUIRED 0 +#endif +#ifndef FIDO_CRED_PROT_UV_OPTIONAL_WITH_ID +#define FIDO_CRED_PROT_UV_OPTIONAL_WITH_ID 0 +#endif + +#ifndef SK_STANDALONE +# include "log.h" +# include "xmalloc.h" +# include "misc.h" +/* + * If building as part of OpenSSH, then rename exported functions. + * This must be done before including sk-api.h. + */ +# define sk_api_version ssh_sk_api_version +# define sk_enroll ssh_sk_enroll +# define sk_sign ssh_sk_sign +# define sk_load_resident_keys ssh_sk_load_resident_keys +#endif /* !SK_STANDALONE */ + +#include "sk-api.h" + +/* #define SK_DEBUG 1 */ + +#ifdef SK_DEBUG +#define SSH_FIDO_INIT_ARG FIDO_DEBUG +#else +#define SSH_FIDO_INIT_ARG 0 +#endif + +#define MAX_FIDO_DEVICES 8 +#define FIDO_POLL_MS 50 +#define SELECT_MS 15000 +#define POLL_SLEEP_NS 200000000 + +/* Compatibility with OpenSSH 1.0.x */ +#if (OPENSSL_VERSION_NUMBER < 0x10100000L) +#define ECDSA_SIG_get0(sig, pr, ps) \ + do { \ + (*pr) = sig->r; \ + (*ps) = sig->s; \ + } while (0) +#endif + +struct sk_usbhid { + fido_dev_t *dev; + char *path; +}; + +/* Return the version of the middleware API */ +uint32_t sk_api_version(void); + +/* Enroll a U2F key (private key generation) */ +int sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len, + const char *application, uint8_t flags, const char *pin, + struct sk_option **options, struct sk_enroll_response **enroll_response); + +/* Sign a challenge */ +int sk_sign(uint32_t alg, const uint8_t *message, size_t message_len, + const char *application, const uint8_t *key_handle, size_t key_handle_len, + uint8_t flags, const char *pin, struct sk_option **options, + struct sk_sign_response **sign_response); + +/* Load resident keys */ +int sk_load_resident_keys(const char *pin, struct sk_option **options, + struct sk_resident_key ***rks, size_t *nrks); + +static void skdebug(const char *func, const char *fmt, ...) + __attribute__((__format__ (printf, 2, 3))); + +static void +skdebug(const char *func, const char *fmt, ...) +{ +#if !defined(SK_STANDALONE) + char *msg; + va_list ap; + + va_start(ap, fmt); + xvasprintf(&msg, fmt, ap); + va_end(ap); + debug("%s: %s", func, msg); + free(msg); +#elif defined(SK_DEBUG) + va_list ap; + + va_start(ap, fmt); + fprintf(stderr, "%s: ", func); + vfprintf(stderr, fmt, ap); + fputc('\n', stderr); + va_end(ap); +#else + (void)func; /* XXX */ + (void)fmt; /* XXX */ +#endif +} + +uint32_t +sk_api_version(void) +{ + return SSH_SK_VERSION_MAJOR; +} + +static struct sk_usbhid * +sk_open(const char *path) +{ + struct sk_usbhid *sk; + int r; + + if (path == NULL) { + skdebug(__func__, "path == NULL"); + return NULL; + } + if ((sk = calloc(1, sizeof(*sk))) == NULL) { + skdebug(__func__, "calloc sk failed"); + return NULL; + } + if ((sk->path = strdup(path)) == NULL) { + skdebug(__func__, "strdup path failed"); + free(sk); + return NULL; + } + if ((sk->dev = fido_dev_new()) == NULL) { + skdebug(__func__, "fido_dev_new failed"); + free(sk->path); + free(sk); + return NULL; + } + if ((r = fido_dev_open(sk->dev, sk->path)) != FIDO_OK) { + skdebug(__func__, "fido_dev_open %s failed: %s", sk->path, + fido_strerr(r)); + fido_dev_free(&sk->dev); + free(sk->path); + free(sk); + return NULL; + } + return sk; +} + +static void +sk_close(struct sk_usbhid *sk) +{ + if (sk == NULL) + return; + fido_dev_cancel(sk->dev); /* cancel any pending operation */ + fido_dev_close(sk->dev); + fido_dev_free(&sk->dev); + free(sk->path); + free(sk); +} + +static struct sk_usbhid ** +sk_openv(const fido_dev_info_t *devlist, size_t ndevs, size_t *nopen) +{ + const fido_dev_info_t *di; + struct sk_usbhid **skv; + size_t i; + + *nopen = 0; + if ((skv = calloc(ndevs, sizeof(*skv))) == NULL) { + skdebug(__func__, "calloc skv failed"); + return NULL; + } + for (i = 0; i < ndevs; i++) { + if ((di = fido_dev_info_ptr(devlist, i)) == NULL) + skdebug(__func__, "fido_dev_info_ptr failed"); + else if ((skv[*nopen] = sk_open(fido_dev_info_path(di))) == NULL) + skdebug(__func__, "sk_open failed"); + else + (*nopen)++; + } + if (*nopen == 0) { + for (i = 0; i < ndevs; i++) + sk_close(skv[i]); + free(skv); + skv = NULL; + } + + return skv; +} + +static void +sk_closev(struct sk_usbhid **skv, size_t nsk) +{ + size_t i; + + for (i = 0; i < nsk; i++) + sk_close(skv[i]); + free(skv); +} + +static int +sk_touch_begin(struct sk_usbhid **skv, size_t nsk) +{ + size_t i, ok = 0; + int r; + + for (i = 0; i < nsk; i++) + if ((r = fido_dev_get_touch_begin(skv[i]->dev)) != FIDO_OK) + skdebug(__func__, "fido_dev_get_touch_begin %s failed:" + " %s", skv[i]->path, fido_strerr(r)); + else + ok++; + + return ok ? 0 : -1; +} + +static int +sk_touch_poll(struct sk_usbhid **skv, size_t nsk, int *touch, size_t *idx) +{ + struct timespec ts_pause; + size_t npoll, i; + int r; + + ts_pause.tv_sec = 0; + ts_pause.tv_nsec = POLL_SLEEP_NS; + nanosleep(&ts_pause, NULL); + npoll = nsk; + for (i = 0; i < nsk; i++) { + if (skv[i] == NULL) + continue; /* device discarded */ + skdebug(__func__, "polling %s", skv[i]->path); + if ((r = fido_dev_get_touch_status(skv[i]->dev, touch, + FIDO_POLL_MS)) != FIDO_OK) { + skdebug(__func__, "fido_dev_get_touch_status %s: %s", + skv[i]->path, fido_strerr(r)); + sk_close(skv[i]); /* discard device */ + skv[i] = NULL; + if (--npoll == 0) { + skdebug(__func__, "no device left to poll"); + return -1; + } + } else if (*touch) { + *idx = i; + return 0; + } + } + *touch = 0; + return 0; +} + +/* Calculate SHA256(m) */ +static int +sha256_mem(const void *m, size_t mlen, u_char *d, size_t dlen) +{ +#ifdef WITH_OPENSSL + u_int mdlen; +#endif + + if (dlen != 32) + return -1; +#ifdef WITH_OPENSSL + mdlen = dlen; + if (!EVP_Digest(m, mlen, d, &mdlen, EVP_sha256(), NULL)) + return -1; +#else + SHA256Data(m, mlen, d); +#endif + return 0; +} + +/* Check if the specified key handle exists on a given sk. */ +static int +sk_try(const struct sk_usbhid *sk, const char *application, + const uint8_t *key_handle, size_t key_handle_len) +{ + fido_assert_t *assert = NULL; + /* generate an invalid signature on FIDO2 tokens */ + const char *data = ""; + uint8_t message[32]; + int r = FIDO_ERR_INTERNAL; + + if (sha256_mem(data, strlen(data), message, sizeof(message)) != 0) { + skdebug(__func__, "hash message failed"); + goto out; + } + if ((assert = fido_assert_new()) == NULL) { + skdebug(__func__, "fido_assert_new failed"); + goto out; + } + if ((r = fido_assert_set_clientdata_hash(assert, message, + sizeof(message))) != FIDO_OK) { + skdebug(__func__, "fido_assert_set_clientdata_hash: %s", + fido_strerr(r)); + goto out; + } + if ((r = fido_assert_set_rp(assert, application)) != FIDO_OK) { + skdebug(__func__, "fido_assert_set_rp: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_assert_allow_cred(assert, key_handle, + key_handle_len)) != FIDO_OK) { + skdebug(__func__, "fido_assert_allow_cred: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_assert_set_up(assert, FIDO_OPT_FALSE)) != FIDO_OK) { + skdebug(__func__, "fido_assert_up: %s", fido_strerr(r)); + goto out; + } + r = fido_dev_get_assert(sk->dev, assert, NULL); + skdebug(__func__, "fido_dev_get_assert: %s", fido_strerr(r)); + if (r == FIDO_ERR_USER_PRESENCE_REQUIRED) { + /* U2F tokens may return this */ + r = FIDO_OK; + } + out: + fido_assert_free(&assert); + + return r != FIDO_OK ? -1 : 0; +} + +static struct sk_usbhid * +sk_select_by_cred(const fido_dev_info_t *devlist, size_t ndevs, + const char *application, const uint8_t *key_handle, size_t key_handle_len) +{ + struct sk_usbhid **skv, *sk; + size_t skvcnt, i; + + if ((skv = sk_openv(devlist, ndevs, &skvcnt)) == NULL) { + skdebug(__func__, "sk_openv failed"); + return NULL; + } + if (skvcnt == 1) { + sk = skv[0]; + skv[0] = NULL; + goto out; + } + sk = NULL; + for (i = 0; i < skvcnt; i++) { + if (sk_try(skv[i], application, key_handle, + key_handle_len) == 0) { + sk = skv[i]; + skv[i] = NULL; + skdebug(__func__, "found key in %s", sk->path); + break; + } + } + out: + sk_closev(skv, skvcnt); + return sk; +} + +static struct sk_usbhid * +sk_select_by_touch(const fido_dev_info_t *devlist, size_t ndevs) +{ + struct sk_usbhid **skv, *sk; + struct timeval tv_start, tv_now, tv_delta; + size_t skvcnt, idx; + int touch, ms_remain; + + if ((skv = sk_openv(devlist, ndevs, &skvcnt)) == NULL) { + skdebug(__func__, "sk_openv failed"); + return NULL; + } + sk = NULL; + if (skvcnt < 2) { + if (skvcnt == 1) { + /* single candidate */ + sk = skv[0]; + skv[0] = NULL; + } + goto out; + } +#ifndef HAVE_FIDO_DEV_GET_TOUCH_STATUS + skdebug(__func__, "libfido2 version does not support a feature needed for multiple tokens. Please upgrade to >=1.5.0"); + goto out; +#endif + + if (sk_touch_begin(skv, skvcnt) == -1) { + skdebug(__func__, "sk_touch_begin failed"); + goto out; + } + monotime_tv(&tv_start); + do { + if (sk_touch_poll(skv, skvcnt, &touch, &idx) == -1) { + skdebug(__func__, "sk_touch_poll failed"); + goto out; + } + if (touch) { + sk = skv[idx]; + skv[idx] = NULL; + goto out; + } + monotime_tv(&tv_now); + timersub(&tv_now, &tv_start, &tv_delta); + ms_remain = SELECT_MS - tv_delta.tv_sec * 1000 - + tv_delta.tv_usec / 1000; + } while (ms_remain >= FIDO_POLL_MS); + skdebug(__func__, "timeout"); +out: + sk_closev(skv, skvcnt); + return sk; +} + +static struct sk_usbhid * +sk_probe(const char *application, const uint8_t *key_handle, + size_t key_handle_len) +{ + struct sk_usbhid *sk; + fido_dev_info_t *devlist; + size_t ndevs; + int r; + + if ((devlist = fido_dev_info_new(MAX_FIDO_DEVICES)) == NULL) { + skdebug(__func__, "fido_dev_info_new failed"); + return NULL; + } + if ((r = fido_dev_info_manifest(devlist, MAX_FIDO_DEVICES, + &ndevs)) != FIDO_OK) { + skdebug(__func__, "fido_dev_info_manifest failed: %s", + fido_strerr(r)); + fido_dev_info_free(&devlist, MAX_FIDO_DEVICES); + return NULL; + } + skdebug(__func__, "%zu device(s) detected", ndevs); + if (ndevs == 0) { + sk = NULL; + } else if (application != NULL && key_handle != NULL) { + skdebug(__func__, "selecting sk by cred"); + sk = sk_select_by_cred(devlist, ndevs, application, key_handle, + key_handle_len); + } else { + skdebug(__func__, "selecting sk by touch"); + sk = sk_select_by_touch(devlist, ndevs); + } + fido_dev_info_free(&devlist, MAX_FIDO_DEVICES); + return sk; +} + +#ifdef WITH_OPENSSL +/* + * The key returned via fido_cred_pubkey_ptr() is in affine coordinates, + * but the API expects a SEC1 octet string. + */ +static int +pack_public_key_ecdsa(const fido_cred_t *cred, + struct sk_enroll_response *response) +{ + const uint8_t *ptr; + BIGNUM *x = NULL, *y = NULL; + EC_POINT *q = NULL; + EC_GROUP *g = NULL; + int ret = -1; + + response->public_key = NULL; + response->public_key_len = 0; + + if ((x = BN_new()) == NULL || + (y = BN_new()) == NULL || + (g = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1)) == NULL || + (q = EC_POINT_new(g)) == NULL) { + skdebug(__func__, "libcrypto setup failed"); + goto out; + } + if ((ptr = fido_cred_pubkey_ptr(cred)) == NULL) { + skdebug(__func__, "fido_cred_pubkey_ptr failed"); + goto out; + } + if (fido_cred_pubkey_len(cred) != 64) { + skdebug(__func__, "bad fido_cred_pubkey_len %zu", + fido_cred_pubkey_len(cred)); + goto out; + } + + if (BN_bin2bn(ptr, 32, x) == NULL || + BN_bin2bn(ptr + 32, 32, y) == NULL) { + skdebug(__func__, "BN_bin2bn failed"); + goto out; + } + if (EC_POINT_set_affine_coordinates_GFp(g, q, x, y, NULL) != 1) { + skdebug(__func__, "EC_POINT_set_affine_coordinates_GFp failed"); + goto out; + } + response->public_key_len = EC_POINT_point2oct(g, q, + POINT_CONVERSION_UNCOMPRESSED, NULL, 0, NULL); + if (response->public_key_len == 0 || response->public_key_len > 2048) { + skdebug(__func__, "bad pubkey length %zu", + response->public_key_len); + goto out; + } + if ((response->public_key = malloc(response->public_key_len)) == NULL) { + skdebug(__func__, "malloc pubkey failed"); + goto out; + } + if (EC_POINT_point2oct(g, q, POINT_CONVERSION_UNCOMPRESSED, + response->public_key, response->public_key_len, NULL) == 0) { + skdebug(__func__, "EC_POINT_point2oct failed"); + goto out; + } + /* success */ + ret = 0; + out: + if (ret != 0 && response->public_key != NULL) { + memset(response->public_key, 0, response->public_key_len); + free(response->public_key); + response->public_key = NULL; + } + EC_POINT_free(q); + EC_GROUP_free(g); + BN_clear_free(x); + BN_clear_free(y); + return ret; +} +#endif /* WITH_OPENSSL */ + +static int +pack_public_key_ed25519(const fido_cred_t *cred, + struct sk_enroll_response *response) +{ + const uint8_t *ptr; + size_t len; + int ret = -1; + + response->public_key = NULL; + response->public_key_len = 0; + + if ((len = fido_cred_pubkey_len(cred)) != 32) { + skdebug(__func__, "bad fido_cred_pubkey_len len %zu", len); + goto out; + } + if ((ptr = fido_cred_pubkey_ptr(cred)) == NULL) { + skdebug(__func__, "fido_cred_pubkey_ptr failed"); + goto out; + } + response->public_key_len = len; + if ((response->public_key = malloc(response->public_key_len)) == NULL) { + skdebug(__func__, "malloc pubkey failed"); + goto out; + } + memcpy(response->public_key, ptr, len); + ret = 0; + out: + if (ret != 0) + free(response->public_key); + return ret; +} + +static int +pack_public_key(uint32_t alg, const fido_cred_t *cred, + struct sk_enroll_response *response) +{ + switch(alg) { +#ifdef WITH_OPENSSL + case SSH_SK_ECDSA: + return pack_public_key_ecdsa(cred, response); +#endif /* WITH_OPENSSL */ + case SSH_SK_ED25519: + return pack_public_key_ed25519(cred, response); + default: + return -1; + } +} + +static int +fidoerr_to_skerr(int fidoerr) +{ + switch (fidoerr) { + case FIDO_ERR_UNSUPPORTED_OPTION: + case FIDO_ERR_UNSUPPORTED_ALGORITHM: + return SSH_SK_ERR_UNSUPPORTED; + case FIDO_ERR_PIN_REQUIRED: + case FIDO_ERR_PIN_INVALID: + return SSH_SK_ERR_PIN_REQUIRED; + default: + return -1; + } +} + +static int +check_enroll_options(struct sk_option **options, char **devicep, + uint8_t *user_id, size_t user_id_len) +{ + size_t i; + + if (options == NULL) + return 0; + for (i = 0; options[i] != NULL; i++) { + if (strcmp(options[i]->name, "device") == 0) { + if ((*devicep = strdup(options[i]->value)) == NULL) { + skdebug(__func__, "strdup device failed"); + return -1; + } + skdebug(__func__, "requested device %s", *devicep); + } else if (strcmp(options[i]->name, "user") == 0) { + if (strlcpy(user_id, options[i]->value, user_id_len) >= + user_id_len) { + skdebug(__func__, "user too long"); + return -1; + } + skdebug(__func__, "requested user %s", + (char *)user_id); + } else { + skdebug(__func__, "requested unsupported option %s", + options[i]->name); + if (options[i]->required) { + skdebug(__func__, "unknown required option"); + return -1; + } + } + } + return 0; +} + +int +sk_enroll(uint32_t alg, const uint8_t *challenge, size_t challenge_len, + const char *application, uint8_t flags, const char *pin, + struct sk_option **options, struct sk_enroll_response **enroll_response) +{ + fido_cred_t *cred = NULL; + const uint8_t *ptr; + uint8_t user_id[32]; + struct sk_usbhid *sk = NULL; + struct sk_enroll_response *response = NULL; + size_t len; + int credprot; + int cose_alg; + int ret = SSH_SK_ERR_GENERAL; + int r; + char *device = NULL; + + fido_init(SSH_FIDO_INIT_ARG); + + if (enroll_response == NULL) { + skdebug(__func__, "enroll_response == NULL"); + goto out; + } + *enroll_response = NULL; + memset(user_id, 0, sizeof(user_id)); + if (check_enroll_options(options, &device, user_id, + sizeof(user_id)) != 0) + goto out; /* error already logged */ + + switch(alg) { +#ifdef WITH_OPENSSL + case SSH_SK_ECDSA: + cose_alg = COSE_ES256; + break; +#endif /* WITH_OPENSSL */ + case SSH_SK_ED25519: + cose_alg = COSE_EDDSA; + break; + default: + skdebug(__func__, "unsupported key type %d", alg); + goto out; + } + if (device != NULL) + sk = sk_open(device); + else + sk = sk_probe(NULL, NULL, 0); + if (sk == NULL) { + skdebug(__func__, "failed to find sk"); + goto out; + } + skdebug(__func__, "using device %s", sk->path); + if ((cred = fido_cred_new()) == NULL) { + skdebug(__func__, "fido_cred_new failed"); + goto out; + } + if ((r = fido_cred_set_type(cred, cose_alg)) != FIDO_OK) { + skdebug(__func__, "fido_cred_set_type: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_cred_set_clientdata_hash(cred, challenge, + challenge_len)) != FIDO_OK) { + skdebug(__func__, "fido_cred_set_clientdata_hash: %s", + fido_strerr(r)); + goto out; + } + if ((r = fido_cred_set_rk(cred, (flags & SSH_SK_RESIDENT_KEY) != 0 ? + FIDO_OPT_TRUE : FIDO_OPT_OMIT)) != FIDO_OK) { + skdebug(__func__, "fido_cred_set_rk: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_cred_set_user(cred, user_id, sizeof(user_id), + "openssh", "openssh", NULL)) != FIDO_OK) { + skdebug(__func__, "fido_cred_set_user: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_cred_set_rp(cred, application, NULL)) != FIDO_OK) { + skdebug(__func__, "fido_cred_set_rp: %s", fido_strerr(r)); + goto out; + } + if ((flags & (SSH_SK_RESIDENT_KEY|SSH_SK_USER_VERIFICATION_REQD)) != 0) { +#if !defined(HAVE_FIDO_DEV_SUPPORTS_CRED_PROT) || \ + !defined(HAVE_FIDO_CRED_SET_PROT) + skdebug(__func__, "libfido2 version does not support a feature required for this operation. Please upgrade to >=1.5.0"); + ret = SSH_SK_ERR_UNSUPPORTED; + goto out; + credprot = 0; (void)credprot; /* avoid warning */ +#endif + if (!fido_dev_supports_cred_prot(sk->dev)) { + skdebug(__func__, "%s does not support credprot, " + "refusing to create unprotected " + "resident/verify-required key", sk->path); + ret = SSH_SK_ERR_UNSUPPORTED; + goto out; + } + if ((flags & SSH_SK_USER_VERIFICATION_REQD)) + credprot = FIDO_CRED_PROT_UV_REQUIRED; + else + credprot = FIDO_CRED_PROT_UV_OPTIONAL_WITH_ID; + + if ((r = fido_cred_set_prot(cred, credprot)) != FIDO_OK) { + skdebug(__func__, "fido_cred_set_prot: %s", + fido_strerr(r)); + ret = fidoerr_to_skerr(r); + goto out; + } + } + if ((r = fido_dev_make_cred(sk->dev, cred, pin)) != FIDO_OK) { + skdebug(__func__, "fido_dev_make_cred: %s", fido_strerr(r)); + ret = fidoerr_to_skerr(r); + goto out; + } + if (fido_cred_x5c_ptr(cred) != NULL) { + if ((r = fido_cred_verify(cred)) != FIDO_OK) { + skdebug(__func__, "fido_cred_verify: %s", + fido_strerr(r)); + goto out; + } + } else { + skdebug(__func__, "self-attested credential"); + if ((r = fido_cred_verify_self(cred)) != FIDO_OK) { + skdebug(__func__, "fido_cred_verify_self: %s", + fido_strerr(r)); + goto out; + } + } + if ((response = calloc(1, sizeof(*response))) == NULL) { + skdebug(__func__, "calloc response failed"); + goto out; + } + if (pack_public_key(alg, cred, response) != 0) { + skdebug(__func__, "pack_public_key failed"); + goto out; + } + if ((ptr = fido_cred_id_ptr(cred)) != NULL) { + len = fido_cred_id_len(cred); + if ((response->key_handle = calloc(1, len)) == NULL) { + skdebug(__func__, "calloc key handle failed"); + goto out; + } + memcpy(response->key_handle, ptr, len); + response->key_handle_len = len; + } + if ((ptr = fido_cred_sig_ptr(cred)) != NULL) { + len = fido_cred_sig_len(cred); + if ((response->signature = calloc(1, len)) == NULL) { + skdebug(__func__, "calloc signature failed"); + goto out; + } + memcpy(response->signature, ptr, len); + response->signature_len = len; + } + if ((ptr = fido_cred_x5c_ptr(cred)) != NULL) { + len = fido_cred_x5c_len(cred); + debug3("%s: attestation cert len=%zu", __func__, len); + if ((response->attestation_cert = calloc(1, len)) == NULL) { + skdebug(__func__, "calloc attestation cert failed"); + goto out; + } + memcpy(response->attestation_cert, ptr, len); + response->attestation_cert_len = len; + } + if ((ptr = fido_cred_authdata_ptr(cred)) != NULL) { + len = fido_cred_authdata_len(cred); + debug3("%s: authdata len=%zu", __func__, len); + if ((response->authdata = calloc(1, len)) == NULL) { + skdebug(__func__, "calloc authdata failed"); + goto out; + } + memcpy(response->authdata, ptr, len); + response->authdata_len = len; + } + *enroll_response = response; + response = NULL; + ret = 0; + out: + free(device); + if (response != NULL) { + free(response->public_key); + free(response->key_handle); + free(response->signature); + free(response->attestation_cert); + free(response->authdata); + free(response); + } + sk_close(sk); + fido_cred_free(&cred); + return ret; +} + +#ifdef WITH_OPENSSL +static int +pack_sig_ecdsa(fido_assert_t *assert, struct sk_sign_response *response) +{ + ECDSA_SIG *sig = NULL; + const BIGNUM *sig_r, *sig_s; + const unsigned char *cp; + size_t sig_len; + int ret = -1; + + cp = fido_assert_sig_ptr(assert, 0); + sig_len = fido_assert_sig_len(assert, 0); + if ((sig = d2i_ECDSA_SIG(NULL, &cp, sig_len)) == NULL) { + skdebug(__func__, "d2i_ECDSA_SIG failed"); + goto out; + } + ECDSA_SIG_get0(sig, &sig_r, &sig_s); + response->sig_r_len = BN_num_bytes(sig_r); + response->sig_s_len = BN_num_bytes(sig_s); + if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL || + (response->sig_s = calloc(1, response->sig_s_len)) == NULL) { + skdebug(__func__, "calloc signature failed"); + goto out; + } + BN_bn2bin(sig_r, response->sig_r); + BN_bn2bin(sig_s, response->sig_s); + ret = 0; + out: + ECDSA_SIG_free(sig); + if (ret != 0) { + free(response->sig_r); + free(response->sig_s); + response->sig_r = NULL; + response->sig_s = NULL; + } + return ret; +} +#endif /* WITH_OPENSSL */ + +static int +pack_sig_ed25519(fido_assert_t *assert, struct sk_sign_response *response) +{ + const unsigned char *ptr; + size_t len; + int ret = -1; + + ptr = fido_assert_sig_ptr(assert, 0); + len = fido_assert_sig_len(assert, 0); + if (len != 64) { + skdebug(__func__, "bad length %zu", len); + goto out; + } + response->sig_r_len = len; + if ((response->sig_r = calloc(1, response->sig_r_len)) == NULL) { + skdebug(__func__, "calloc signature failed"); + goto out; + } + memcpy(response->sig_r, ptr, len); + ret = 0; + out: + if (ret != 0) { + free(response->sig_r); + response->sig_r = NULL; + } + return ret; +} + +static int +pack_sig(uint32_t alg, fido_assert_t *assert, + struct sk_sign_response *response) +{ + switch(alg) { +#ifdef WITH_OPENSSL + case SSH_SK_ECDSA: + return pack_sig_ecdsa(assert, response); +#endif /* WITH_OPENSSL */ + case SSH_SK_ED25519: + return pack_sig_ed25519(assert, response); + default: + return -1; + } +} + +/* Checks sk_options for sk_sign() and sk_load_resident_keys() */ +static int +check_sign_load_resident_options(struct sk_option **options, char **devicep) +{ + size_t i; + + if (options == NULL) + return 0; + for (i = 0; options[i] != NULL; i++) { + if (strcmp(options[i]->name, "device") == 0) { + if ((*devicep = strdup(options[i]->value)) == NULL) { + skdebug(__func__, "strdup device failed"); + return -1; + } + skdebug(__func__, "requested device %s", *devicep); + } else { + skdebug(__func__, "requested unsupported option %s", + options[i]->name); + if (options[i]->required) { + skdebug(__func__, "unknown required option"); + return -1; + } + } + } + return 0; +} + +int +sk_sign(uint32_t alg, const uint8_t *data, size_t datalen, + const char *application, + const uint8_t *key_handle, size_t key_handle_len, + uint8_t flags, const char *pin, struct sk_option **options, + struct sk_sign_response **sign_response) +{ + fido_assert_t *assert = NULL; + char *device = NULL; + struct sk_usbhid *sk = NULL; + struct sk_sign_response *response = NULL; + uint8_t message[32]; + int ret = SSH_SK_ERR_GENERAL; + int r; + + fido_init(SSH_FIDO_INIT_ARG); + + if (sign_response == NULL) { + skdebug(__func__, "sign_response == NULL"); + goto out; + } + *sign_response = NULL; + if (check_sign_load_resident_options(options, &device) != 0) + goto out; /* error already logged */ + /* hash data to be signed before it goes to the security key */ + if ((r = sha256_mem(data, datalen, message, sizeof(message))) != 0) { + skdebug(__func__, "hash message failed"); + goto out; + } + if (device != NULL) + sk = sk_open(device); + else if (pin != NULL || (flags & SSH_SK_USER_VERIFICATION_REQD)) + sk = sk_probe(NULL, NULL, 0); + else + sk = sk_probe(application, key_handle, key_handle_len); + if (sk == NULL) { + skdebug(__func__, "failed to find sk"); + goto out; + } + if ((assert = fido_assert_new()) == NULL) { + skdebug(__func__, "fido_assert_new failed"); + goto out; + } + if ((r = fido_assert_set_clientdata_hash(assert, message, + sizeof(message))) != FIDO_OK) { + skdebug(__func__, "fido_assert_set_clientdata_hash: %s", + fido_strerr(r)); + goto out; + } + if ((r = fido_assert_set_rp(assert, application)) != FIDO_OK) { + skdebug(__func__, "fido_assert_set_rp: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_assert_allow_cred(assert, key_handle, + key_handle_len)) != FIDO_OK) { + skdebug(__func__, "fido_assert_allow_cred: %s", fido_strerr(r)); + goto out; + } + if ((r = fido_assert_set_up(assert, + (flags & SSH_SK_USER_PRESENCE_REQD) ? + FIDO_OPT_TRUE : FIDO_OPT_FALSE)) != FIDO_OK) { + skdebug(__func__, "fido_assert_set_up: %s", fido_strerr(r)); + goto out; + } + if (pin == NULL && (flags & SSH_SK_USER_VERIFICATION_REQD) && + (r = fido_assert_set_uv(assert, FIDO_OPT_TRUE)) != FIDO_OK) { + skdebug(__func__, "fido_assert_set_uv: %s", fido_strerr(r)); + ret = FIDO_ERR_PIN_REQUIRED; + goto out; + } + if ((r = fido_dev_get_assert(sk->dev, assert, pin)) != FIDO_OK) { + skdebug(__func__, "fido_dev_get_assert: %s", fido_strerr(r)); + ret = fidoerr_to_skerr(r); + goto out; + } + if ((response = calloc(1, sizeof(*response))) == NULL) { + skdebug(__func__, "calloc response failed"); + goto out; + } + response->flags = fido_assert_flags(assert, 0); + response->counter = fido_assert_sigcount(assert, 0); + if (pack_sig(alg, assert, response) != 0) { + skdebug(__func__, "pack_sig failed"); + goto out; + } + *sign_response = response; + response = NULL; + ret = 0; + out: + explicit_bzero(message, sizeof(message)); + free(device); + if (response != NULL) { + free(response->sig_r); + free(response->sig_s); + free(response); + } + sk_close(sk); + fido_assert_free(&assert); + return ret; +} + +static int +read_rks(struct sk_usbhid *sk, const char *pin, + struct sk_resident_key ***rksp, size_t *nrksp) +{ + int ret = SSH_SK_ERR_GENERAL, r = -1; + fido_credman_metadata_t *metadata = NULL; + fido_credman_rp_t *rp = NULL; + fido_credman_rk_t *rk = NULL; + size_t i, j, nrp, nrk; + const fido_cred_t *cred; + struct sk_resident_key *srk = NULL, **tmp; + + if (pin == NULL) { + skdebug(__func__, "no PIN specified"); + ret = SSH_SK_ERR_PIN_REQUIRED; + goto out; + } + if ((metadata = fido_credman_metadata_new()) == NULL) { + skdebug(__func__, "alloc failed"); + goto out; + } + + if ((r = fido_credman_get_dev_metadata(sk->dev, metadata, pin)) != 0) { + if (r == FIDO_ERR_INVALID_COMMAND) { + skdebug(__func__, "device %s does not support " + "resident keys", sk->path); + ret = 0; + goto out; + } + skdebug(__func__, "get metadata for %s failed: %s", + sk->path, fido_strerr(r)); + ret = fidoerr_to_skerr(r); + goto out; + } + skdebug(__func__, "existing %llu, remaining %llu", + (unsigned long long)fido_credman_rk_existing(metadata), + (unsigned long long)fido_credman_rk_remaining(metadata)); + if ((rp = fido_credman_rp_new()) == NULL) { + skdebug(__func__, "alloc rp failed"); + goto out; + } + if ((r = fido_credman_get_dev_rp(sk->dev, rp, pin)) != 0) { + skdebug(__func__, "get RPs for %s failed: %s", + sk->path, fido_strerr(r)); + goto out; + } + nrp = fido_credman_rp_count(rp); + skdebug(__func__, "Device %s has resident keys for %zu RPs", + sk->path, nrp); + + /* Iterate over RP IDs that have resident keys */ + for (i = 0; i < nrp; i++) { + skdebug(__func__, "rp %zu: name=\"%s\" id=\"%s\" hashlen=%zu", + i, fido_credman_rp_name(rp, i), fido_credman_rp_id(rp, i), + fido_credman_rp_id_hash_len(rp, i)); + + /* Skip non-SSH RP IDs */ + if (strncasecmp(fido_credman_rp_id(rp, i), "ssh:", 4) != 0) + continue; + + fido_credman_rk_free(&rk); + if ((rk = fido_credman_rk_new()) == NULL) { + skdebug(__func__, "alloc rk failed"); + goto out; + } + if ((r = fido_credman_get_dev_rk(sk->dev, + fido_credman_rp_id(rp, i), rk, pin)) != 0) { + skdebug(__func__, "get RKs for %s slot %zu failed: %s", + sk->path, i, fido_strerr(r)); + goto out; + } + nrk = fido_credman_rk_count(rk); + skdebug(__func__, "RP \"%s\" has %zu resident keys", + fido_credman_rp_id(rp, i), nrk); + + /* Iterate over resident keys for this RP ID */ + for (j = 0; j < nrk; j++) { + if ((cred = fido_credman_rk(rk, j)) == NULL) { + skdebug(__func__, "no RK in slot %zu", j); + continue; + } + skdebug(__func__, "Device %s RP \"%s\" slot %zu: " + "type %d flags 0x%02x prot 0x%02x", sk->path, + fido_credman_rp_id(rp, i), j, fido_cred_type(cred), + fido_cred_flags(cred), fido_cred_prot(cred)); + + /* build response entry */ + if ((srk = calloc(1, sizeof(*srk))) == NULL || + (srk->key.key_handle = calloc(1, + fido_cred_id_len(cred))) == NULL || + (srk->application = strdup(fido_credman_rp_id(rp, + i))) == NULL) { + skdebug(__func__, "alloc sk_resident_key"); + goto out; + } + + srk->key.key_handle_len = fido_cred_id_len(cred); + memcpy(srk->key.key_handle, fido_cred_id_ptr(cred), + srk->key.key_handle_len); + + switch (fido_cred_type(cred)) { + case COSE_ES256: + srk->alg = SSH_SK_ECDSA; + break; + case COSE_EDDSA: + srk->alg = SSH_SK_ED25519; + break; + default: + skdebug(__func__, "unsupported key type %d", + fido_cred_type(cred)); + goto out; /* XXX free rk and continue */ + } + + if (fido_cred_prot(cred) == FIDO_CRED_PROT_UV_REQUIRED) + srk->flags |= SSH_SK_USER_VERIFICATION_REQD; + + if ((r = pack_public_key(srk->alg, cred, + &srk->key)) != 0) { + skdebug(__func__, "pack public key failed"); + goto out; + } + /* append */ + if ((tmp = recallocarray(*rksp, *nrksp, (*nrksp) + 1, + sizeof(**rksp))) == NULL) { + skdebug(__func__, "alloc rksp"); + goto out; + } + *rksp = tmp; + (*rksp)[(*nrksp)++] = srk; + srk = NULL; + } + } + /* Success */ + ret = 0; + out: + if (srk != NULL) { + free(srk->application); + freezero(srk->key.public_key, srk->key.public_key_len); + freezero(srk->key.key_handle, srk->key.key_handle_len); + freezero(srk, sizeof(*srk)); + } + fido_credman_rp_free(&rp); + fido_credman_rk_free(&rk); + fido_credman_metadata_free(&metadata); + return ret; +} + +int +sk_load_resident_keys(const char *pin, struct sk_option **options, + struct sk_resident_key ***rksp, size_t *nrksp) +{ + int ret = SSH_SK_ERR_GENERAL, r = -1; + size_t i, nrks = 0; + struct sk_resident_key **rks = NULL; + struct sk_usbhid *sk = NULL; + char *device = NULL; + + *rksp = NULL; + *nrksp = 0; + + fido_init(SSH_FIDO_INIT_ARG); + + if (check_sign_load_resident_options(options, &device) != 0) + goto out; /* error already logged */ + if (device != NULL) + sk = sk_open(device); + else + sk = sk_probe(NULL, NULL, 0); + if (sk == NULL) { + skdebug(__func__, "failed to find sk"); + goto out; + } + skdebug(__func__, "trying %s", sk->path); + if ((r = read_rks(sk, pin, &rks, &nrks)) != 0) { + skdebug(__func__, "read_rks failed for %s", sk->path); + ret = r; + goto out; + } + /* success, unless we have no keys but a specific error */ + if (nrks > 0 || ret == SSH_SK_ERR_GENERAL) + ret = 0; + *rksp = rks; + *nrksp = nrks; + rks = NULL; + nrks = 0; + out: + sk_close(sk); + for (i = 0; i < nrks; i++) { + free(rks[i]->application); + freezero(rks[i]->key.public_key, rks[i]->key.public_key_len); + freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len); + freezero(rks[i], sizeof(*rks[i])); + } + free(rks); + return ret; +} + +#endif /* ENABLE_SK_INTERNAL */ |