upstream: resident keys support in SK API

Adds a sk_load_resident_keys() function to the security key
API that accepts a security key provider and a PIN and returns
a list of keys.

Implement support for this in the usbhid middleware.

feedback and ok markus@

OpenBSD-Commit-ID: 67e984e4e87f4999ce447a6178c4249a9174eff0

1 files changed, 232 insertions, 6 deletions

diff --git a/sk-usbhid.c b/sk-usbhid.c
index 61b52bbb9..fa4424483 100644
--- a/sk-usbhid.c
+++ b/sk-usbhid.c
@@ -34,6 +34,7 @@
 #endif /* WITH_OPENSSL */
 
 #include <fido.h>
+#include <fido/credman.h>
 
 #ifndef SK_STANDALONE
 #include "log.h"
@@ -84,11 +85,19 @@ struct sk_sign_response {
         size_t sig_s_len;
 };
 
+struct sk_resident_key {
+        uint8_t alg;
+        size_t slot;
+        char *application;
+        struct sk_enroll_response key;
+};
+
 /* If building as part of OpenSSH, then rename exported functions */
 #if !defined(SK_STANDALONE)
-#define sk_api_version  ssh_sk_api_version
-#define sk_enroll       ssh_sk_enroll
-#define sk_sign         ssh_sk_sign
+#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
 
 /* Return the version of the middleware API */
@@ -104,6 +113,10 @@ int sk_sign(int 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, struct sk_sign_response **sign_response);
 
+/* Load resident keys */
+int sk_load_resident_keys(const char *pin,
+    struct sk_resident_key ***rks, size_t *nrks);
+
 static void skdebug(const char *func, const char *fmt, ...)
     __attribute__((__format__ (printf, 2, 3)));
 
@@ -281,7 +294,8 @@ find_device(const uint8_t *message, size_t message_len, const char *application,
  * but the API expects a SEC1 octet string.
  */
 static int
-pack_public_key_ecdsa(fido_cred_t *cred, struct sk_enroll_response *response)
+pack_public_key_ecdsa(const fido_cred_t *cred,
+    struct sk_enroll_response *response)
 {
         const uint8_t *ptr;
         BIGNUM *x = NULL, *y = NULL;
@@ -351,7 +365,8 @@ pack_public_key_ecdsa(fido_cred_t *cred, struct sk_enroll_response *response)
 #endif /* WITH_OPENSSL */
 
 static int
-pack_public_key_ed25519(fido_cred_t *cred, struct sk_enroll_response *response)
+pack_public_key_ed25519(const fido_cred_t *cred,
+    struct sk_enroll_response *response)
 {
         const uint8_t *ptr;
         size_t len;
@@ -382,7 +397,8 @@ pack_public_key_ed25519(fido_cred_t *cred, struct sk_enroll_response *response)
 }
 
 static int
-pack_public_key(int alg, fido_cred_t *cred, struct sk_enroll_response *response)
+pack_public_key(int alg, const fido_cred_t *cred,
+    struct sk_enroll_response *response)
 {
         switch(alg) {
 #ifdef WITH_OPENSSL
@@ -715,4 +731,214 @@ sk_sign(int alg, const uint8_t *message, size_t message_len,
         }
         return ret;
 }
+
+static int
+read_rks(const char *devpath, const char *pin,
+    struct sk_resident_key ***rksp, size_t *nrksp)
+{
+        int r = -1;
+        fido_dev_t *dev = NULL;
+        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 ((dev = fido_dev_new()) == NULL) {
+                skdebug(__func__, "fido_dev_new failed");
+                return -1;
+        }
+        if ((r = fido_dev_open(dev, devpath)) != FIDO_OK) {
+                skdebug(__func__, "fido_dev_open %s failed: %s",
+                    devpath, fido_strerr(r));
+                fido_dev_free(&dev);
+                return -1;
+        }
+        if ((metadata = fido_credman_metadata_new()) == NULL) {
+                r = -1;
+                skdebug(__func__, "alloc failed");
+                goto out;
+        }
+
+        if ((r = fido_credman_get_dev_metadata(dev, metadata, pin)) != 0) {
+                if (r == FIDO_ERR_INVALID_COMMAND) {
+                        skdebug(__func__, "device %s does not support "
+                            "resident keys", devpath);
+                        r = 0;
+                        goto out;
+                }
+                skdebug(__func__, "get metadata for %s failed: %s",
+                    devpath, fido_strerr(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) {
+                r = -1;
+                skdebug(__func__, "alloc rp failed");
+                goto out;
+        }
+        if ((r = fido_credman_get_dev_rp(dev, rp, pin)) != 0) {
+                skdebug(__func__, "get RPs for %s failed: %s",
+                    devpath, fido_strerr(r));
+                goto out;
+        }
+        nrp = fido_credman_rp_count(rp);
+        skdebug(__func__, "Device %s has resident keys for %zu RPs",
+            devpath, 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) {
+                        r = -1;
+                        skdebug(__func__, "alloc rk failed");
+                        goto out;
+                }
+                if ((r = fido_credman_get_dev_rk(dev, fido_credman_rp_id(rp, i),
+                    rk, pin)) != 0) {
+                        skdebug(__func__, "get RKs for %s slot %zu failed: %s",
+                            devpath, 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", devpath, fido_credman_rp_id(rp, i), j,
+                            fido_cred_type(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) {
+                                r = -1;
+                                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 = SK_ECDSA;
+                                break;
+                        case COSE_EDDSA:
+                                srk->alg = SK_ED25519;
+                                break;
+                        default:
+                                skdebug(__func__, "unsupported key type %d",
+                                    fido_cred_type(cred));
+                                goto out;
+                        }
+
+                        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) {
+                                r = -1;
+                                skdebug(__func__, "alloc rksp");
+                                goto out;
+                        }
+                        *rksp = tmp;
+                        (*rksp)[(*nrksp)++] = srk;
+                        srk = NULL;
+                }
+        }
+        /* Success */
+        r = 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_dev_close(dev);
+        fido_dev_free(&dev);
+        fido_credman_metadata_free(&metadata);
+        return r;
+}
+
+int
+sk_load_resident_keys(const char *pin,
+    struct sk_resident_key ***rksp, size_t *nrksp)
+{
+        int r = -1;
+        fido_dev_info_t *devlist = NULL;
+        size_t i, ndev = 0, nrks = 0;
+        const fido_dev_info_t *di;
+        struct sk_resident_key **rks = NULL;
+        *rksp = NULL;
+        *nrksp = 0;
+
+        if ((devlist = fido_dev_info_new(MAX_FIDO_DEVICES)) == NULL) {
+                skdebug(__func__, "fido_dev_info_new failed");
+                goto out;
+        }
+        if ((r = fido_dev_info_manifest(devlist,
+            MAX_FIDO_DEVICES, &ndev)) != FIDO_OK) {
+                skdebug(__func__, "fido_dev_info_manifest failed: %s",
+                    fido_strerr(r));
+                goto out;
+        }
+        for (i = 0; i < ndev; i++) {
+                if ((di = fido_dev_info_ptr(devlist, i)) == NULL) {
+                        skdebug(__func__, "no dev info at %zu", i);
+                        continue;
+                }
+                skdebug(__func__, "trying %s", fido_dev_info_path(di));
+                if ((r = read_rks(fido_dev_info_path(di), pin,
+                    &rks, &nrks)) != 0) {
+                        skdebug(__func__, "read_rks failed for %s",
+                            fido_dev_info_path(di));
+                        continue;
+                }
+        }
+        /* success */
+        r = 0;
+        *rksp = rks;
+        *nrksp = nrks;
+        rks = NULL;
+        nrks = 0;
+ out:
+        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);
+        fido_dev_info_free(&devlist, MAX_FIDO_DEVICES);
+        return r;
+}
+
 #endif /* ENABLE_SK_INTERNAL */