/* $OpenBSD: sshsig.c,v 1.38 2025/02/18 08:02:48 djm Exp $ */
/*
 * Copyright (c) 2019 Google LLC
 *
 * 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"

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

#include "authfd.h"
#include "authfile.h"
#include "log.h"
#include "misc.h"
#include "sshbuf.h"
#include "sshsig.h"
#include "ssherr.h"
#include "sshkey.h"
#include "match.h"
#include "digest.h"

#define SIG_VERSION             0x01
#define MAGIC_PREAMBLE          "SSHSIG"
#define MAGIC_PREAMBLE_LEN      (sizeof(MAGIC_PREAMBLE) - 1)
#define BEGIN_SIGNATURE         "-----BEGIN SSH SIGNATURE-----"
#define END_SIGNATURE           "-----END SSH SIGNATURE-----"
#define RSA_SIGN_ALG            "rsa-sha2-512"
#define RSA_SIGN_ALLOWED        "rsa-sha2-512,rsa-sha2-256"
#define HASHALG_DEFAULT         "sha512"
#define HASHALG_ALLOWED         "sha256,sha512"

int
sshsig_armor(const struct sshbuf *blob, struct sshbuf **out)
{
        struct sshbuf *buf = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;

        *out = NULL;

        if ((buf = sshbuf_new()) == NULL) {
                error_f("sshbuf_new failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }

        if ((r = sshbuf_putf(buf, "%s\n", BEGIN_SIGNATURE)) != 0) {
                error_fr(r, "sshbuf_putf");
                goto out;
        }

        if ((r = sshbuf_dtob64(blob, buf, 1)) != 0) {
                error_fr(r, "base64 encode signature");
                goto out;
        }

        if ((r = sshbuf_put(buf, END_SIGNATURE,
            sizeof(END_SIGNATURE)-1)) != 0 ||
            (r = sshbuf_put_u8(buf, '\n')) != 0) {
                error_fr(r, "sshbuf_put");
                goto out;
        }
        /* success */
        *out = buf;
        buf = NULL; /* transferred */
        r = 0;
 out:
        sshbuf_free(buf);
        return r;
}

int
sshsig_dearmor(struct sshbuf *sig, struct sshbuf **out)
{
        int r;
        size_t eoffset = 0;
        struct sshbuf *buf = NULL;
        struct sshbuf *sbuf = NULL;
        char *b64 = NULL;

        if ((sbuf = sshbuf_fromb(sig)) == NULL) {
                error_f("sshbuf_fromb failed");
                return SSH_ERR_ALLOC_FAIL;
        }

        /* Expect and consume preamble + lf/crlf */
        if ((r = sshbuf_cmp(sbuf, 0,
            BEGIN_SIGNATURE, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
                error("Couldn't parse signature: missing header");
                goto done;
        }
        if ((r = sshbuf_consume(sbuf, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
                error_fr(r, "consume");
                goto done;
        }
        if ((r = sshbuf_cmp(sbuf, 0, "\r\n", 2)) == 0)
                eoffset = 2;
        else if ((r = sshbuf_cmp(sbuf, 0, "\n", 1)) == 0)
                eoffset = 1;
        else {
                r = SSH_ERR_INVALID_FORMAT;
                error_f("no header eol");
                goto done;
        }
        if ((r = sshbuf_consume(sbuf, eoffset)) != 0) {
                error_fr(r, "consume eol");
                goto done;
        }
        /* Find and consume lf + suffix (any prior cr would be ignored) */
        if ((r = sshbuf_find(sbuf, 0, "\n" END_SIGNATURE,
            sizeof(END_SIGNATURE), &eoffset)) != 0) {
                error("Couldn't parse signature: missing footer");
                goto done;
        }
        if ((r = sshbuf_consume_end(sbuf, sshbuf_len(sbuf)-eoffset)) != 0) {
                error_fr(r, "consume");
                goto done;
        }

        if ((b64 = sshbuf_dup_string(sbuf)) == NULL) {
                error_f("sshbuf_dup_string failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto done;
        }

        if ((buf = sshbuf_new()) == NULL) {
                error_f("sshbuf_new() failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto done;
        }

        if ((r = sshbuf_b64tod(buf, b64)) != 0) {
                error_fr(r, "decode base64");
                goto done;
        }

        /* success */
        *out = buf;
        r = 0;
        buf = NULL; /* transferred */
done:
        sshbuf_free(buf);
        sshbuf_free(sbuf);
        free(b64);
        return r;
}

static int
sshsig_wrap_sign(struct sshkey *key, const char *hashalg,
    const char *sk_provider, const char *sk_pin, const struct sshbuf *h_message,
    const char *sig_namespace, struct sshbuf **out,
    sshsig_signer *signer, void *signer_ctx)
{
        int r;
        size_t slen = 0;
        u_char *sig = NULL;
        struct sshbuf *blob = NULL;
        struct sshbuf *tosign = NULL;
        const char *sign_alg = NULL;

        if ((tosign = sshbuf_new()) == NULL ||
            (blob = sshbuf_new()) == NULL) {
                error_f("sshbuf_new failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto done;
        }

        if ((r = sshbuf_put(tosign, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
            (r = sshbuf_put_cstring(tosign, sig_namespace)) != 0 ||
            (r = sshbuf_put_string(tosign, NULL, 0)) != 0 || /* reserved */
            (r = sshbuf_put_cstring(tosign, hashalg)) != 0 ||
            (r = sshbuf_put_stringb(tosign, h_message)) != 0) {
                error_fr(r, "assemble message to sign");
                goto done;
        }

        /* If using RSA keys then default to a good signature algorithm */
        if (sshkey_type_plain(key->type) == KEY_RSA) {
                sign_alg = RSA_SIGN_ALG;
                if (strcmp(hashalg, "sha256") == 0)
                        sign_alg = "rsa-sha2-256";
                else if (strcmp(hashalg, "sha512") == 0)
                        sign_alg = "rsa-sha2-512";
        }

        if (signer != NULL) {
                if ((r = signer(key, &sig, &slen,
                    sshbuf_ptr(tosign), sshbuf_len(tosign),
                    sign_alg, sk_provider, sk_pin, 0, signer_ctx)) != 0) {
                        error_r(r, "Couldn't sign message (signer)");
                        goto done;
                }
        } else {
                if ((r = sshkey_sign(key, &sig, &slen,
                    sshbuf_ptr(tosign), sshbuf_len(tosign),
                    sign_alg, sk_provider, sk_pin, 0)) != 0) {
                        error_r(r, "Couldn't sign message");
                        goto done;
                }
        }

        if ((r = sshbuf_put(blob, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
            (r = sshbuf_put_u32(blob, SIG_VERSION)) != 0 ||
            (r = sshkey_puts(key, blob)) != 0 ||
            (r = sshbuf_put_cstring(blob, sig_namespace)) != 0 ||
            (r = sshbuf_put_string(blob, NULL, 0)) != 0 || /* reserved */
            (r = sshbuf_put_cstring(blob, hashalg)) != 0 ||
            (r = sshbuf_put_string(blob, sig, slen)) != 0) {
                error_fr(r, "assemble signature object");
                goto done;
        }

        if (out != NULL) {
                *out = blob;
                blob = NULL;
        }
        r = 0;
done:
        free(sig);
        sshbuf_free(blob);
        sshbuf_free(tosign);
        return r;
}

/* Check preamble and version. */
static int
sshsig_parse_preamble(struct sshbuf *buf)
{
        int r = SSH_ERR_INTERNAL_ERROR;
        uint32_t sversion;

        if ((r = sshbuf_cmp(buf, 0, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
            (r = sshbuf_consume(buf, (sizeof(MAGIC_PREAMBLE)-1))) != 0 ||
            (r = sshbuf_get_u32(buf, &sversion)) != 0) {
                error("Couldn't verify signature: invalid format");
                return r;
        }

        if (sversion > SIG_VERSION) {
                error("Signature version %lu is larger than supported "
                    "version %u", (unsigned long)sversion, SIG_VERSION);
                return SSH_ERR_INVALID_FORMAT;
        }
        return 0;
}

static int
sshsig_check_hashalg(const char *hashalg)
{
        if (hashalg == NULL ||
            match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
                return 0;
        error_f("unsupported hash algorithm \"%.100s\"", hashalg);
        return SSH_ERR_SIGN_ALG_UNSUPPORTED;
}

static int
sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
{
        struct sshbuf *buf = NULL;
        char *hashalg = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;

        if (hashalgp != NULL)
                *hashalgp = NULL;
        if ((buf = sshbuf_fromb(signature)) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        if ((r = sshsig_parse_preamble(buf)) != 0)
                goto done;
        if ((r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
            (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
            (r = sshbuf_get_string(buf, NULL, NULL)) != 0 ||
            (r = sshbuf_get_cstring(buf, &hashalg, NULL)) != 0 ||
            (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0) {
                error_fr(r, "parse signature object");
                goto done;
        }

        /* success */
        r = 0;
        *hashalgp = hashalg;
        hashalg = NULL;
 done:
        free(hashalg);
        sshbuf_free(buf);
        return r;
}

static int
sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
    const struct sshbuf *h_message, const char *expect_namespace,
    struct sshkey **sign_keyp, struct sshkey_sig_details **sig_details)
{
        int r = SSH_ERR_INTERNAL_ERROR;
        struct sshbuf *buf = NULL, *toverify = NULL;
        struct sshkey *key = NULL;
        const u_char *sig;
        char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL;
        size_t siglen;

        debug_f("verify message length %zu", sshbuf_len(h_message));
        if (sig_details != NULL)
                *sig_details = NULL;
        if (sign_keyp != NULL)
                *sign_keyp = NULL;

        if ((toverify = sshbuf_new()) == NULL) {
                error_f("sshbuf_new failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto done;
        }
        if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE,
            MAGIC_PREAMBLE_LEN)) != 0 ||
            (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 ||
            (r = sshbuf_put_string(toverify, NULL, 0)) != 0 || /* reserved */
            (r = sshbuf_put_cstring(toverify, hashalg)) != 0 ||
            (r = sshbuf_put_stringb(toverify, h_message)) != 0) {
                error_fr(r, "assemble message to verify");
                goto done;
        }

        if ((r = sshsig_parse_preamble(signature)) != 0)
                goto done;

        if ((r = sshkey_froms(signature, &key)) != 0 ||
            (r = sshbuf_get_cstring(signature, &got_namespace, NULL)) != 0 ||
            (r = sshbuf_get_string(signature, NULL, NULL)) != 0 ||
            (r = sshbuf_get_cstring(signature, &sig_hashalg, NULL)) != 0 ||
            (r = sshbuf_get_string_direct(signature, &sig, &siglen)) != 0) {
                error_fr(r, "parse signature object");
                goto done;
        }

        if (sshbuf_len(signature) != 0) {
                error("Signature contains trailing data");
                r = SSH_ERR_INVALID_FORMAT;
                goto done;
        }

        if (strcmp(expect_namespace, got_namespace) != 0) {
                error("Couldn't verify signature: namespace does not match");
                debug_f("expected namespace \"%s\" received \"%s\"",
                    expect_namespace, got_namespace);
                r = SSH_ERR_SIGNATURE_INVALID;
                goto done;
        }
        if (strcmp(hashalg, sig_hashalg) != 0) {
                error("Couldn't verify signature: hash algorithm mismatch");
                debug_f("expected algorithm \"%s\" received \"%s\"",
                    hashalg, sig_hashalg);
                r = SSH_ERR_SIGNATURE_INVALID;
                goto done;
        }
        /* Ensure that RSA keys use an acceptable signature algorithm */
        if (sshkey_type_plain(key->type) == KEY_RSA) {
                if ((r = sshkey_get_sigtype(sig, siglen, &sigtype)) != 0) {
                        error_r(r, "Couldn't verify signature: unable to get "
                            "signature type");
                        goto done;
                }
                if (match_pattern_list(sigtype, RSA_SIGN_ALLOWED, 0) != 1) {
                        error("Couldn't verify signature: unsupported RSA "
                            "signature algorithm %s", sigtype);
                        r = SSH_ERR_SIGN_ALG_UNSUPPORTED;
                        goto done;
                }
        }
        if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify),
            sshbuf_len(toverify), NULL, 0, sig_details)) != 0) {
                error_r(r, "Signature verification failed");
                goto done;
        }

        /* success */
        r = 0;
        if (sign_keyp != NULL) {
                *sign_keyp = key;
                key = NULL; /* transferred */
        }
done:
        free(got_namespace);
        free(sigtype);
        free(sig_hashalg);
        sshbuf_free(buf);
        sshbuf_free(toverify);
        sshkey_free(key);
        return r;
}

static int
hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp)
{
        char *hex, hash[SSH_DIGEST_MAX_LENGTH];
        int alg, r = SSH_ERR_INTERNAL_ERROR;
        struct sshbuf *b = NULL;

        *bp = NULL;
        memset(hash, 0, sizeof(hash));

        if ((r = sshsig_check_hashalg(hashalg)) != 0)
                return r;
        if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
                error_f("can't look up hash algorithm %s", hashalg);
                return SSH_ERR_INTERNAL_ERROR;
        }
        if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
                error_fr(r, "ssh_digest_buffer");
                return r;
        }
        if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
                debug3_f("final hash: %s", hex);
                freezero(hex, strlen(hex));
        }
        if ((b = sshbuf_new()) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
                error_fr(r, "sshbuf_put");
                goto out;
        }
        *bp = b;
        b = NULL; /* transferred */
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        explicit_bzero(hash, sizeof(hash));
        return r;
}

int
sshsig_signb(struct sshkey *key, const char *hashalg,
    const char *sk_provider, const char *sk_pin,
    const struct sshbuf *message, const char *sig_namespace,
    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
{
        struct sshbuf *b = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;

        if (hashalg == NULL)
                hashalg = HASHALG_DEFAULT;
        if (out != NULL)
                *out = NULL;
        if ((r = hash_buffer(message, hashalg, &b)) != 0) {
                error_fr(r, "hash buffer");
                goto out;
        }
        if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b,
            sig_namespace, out, signer, signer_ctx)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        return r;
}

int
sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
    const char *expect_namespace, struct sshkey **sign_keyp,
    struct sshkey_sig_details **sig_details)
{
        struct sshbuf *b = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;
        char *hashalg = NULL;

        if (sig_details != NULL)
                *sig_details = NULL;
        if (sign_keyp != NULL)
                *sign_keyp = NULL;
        if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
                return r;
        debug_f("signature made with hash \"%s\"", hashalg);
        if ((r = hash_buffer(message, hashalg, &b)) != 0) {
                error_fr(r, "hash buffer");
                goto out;
        }
        if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
            sign_keyp, sig_details)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        free(hashalg);
        return r;
}

static int
hash_file(int fd, const char *hashalg, struct sshbuf **bp)
{
        char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH];
        ssize_t n, total = 0;
        struct ssh_digest_ctx *ctx = NULL;
        int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR;
        struct sshbuf *b = NULL;

        *bp = NULL;
        memset(hash, 0, sizeof(hash));

        if ((r = sshsig_check_hashalg(hashalg)) != 0)
                return r;
        if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
                error_f("can't look up hash algorithm %s", hashalg);
                return SSH_ERR_INTERNAL_ERROR;
        }
        if ((ctx = ssh_digest_start(alg)) == NULL) {
                error_f("ssh_digest_start failed");
                return SSH_ERR_INTERNAL_ERROR;
        }
        for (;;) {
                if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) {
                        if (errno == EINTR || errno == EAGAIN)
                                continue;
                        oerrno = errno;
                        error_f("read: %s", strerror(errno));
                        errno = oerrno;
                        r = SSH_ERR_SYSTEM_ERROR;
                        goto out;
                } else if (n == 0) {
                        debug2_f("hashed %zu bytes", total);
                        break; /* EOF */
                }
                total += (size_t)n;
                if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
                        error_fr(r, "ssh_digest_update");
                        goto out;
                }
        }
        if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
                error_fr(r, "ssh_digest_final");
                goto out;
        }
        if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
                debug3_f("final hash: %s", hex);
                freezero(hex, strlen(hex));
        }
        if ((b = sshbuf_new()) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
                error_fr(r, "sshbuf_put");
                goto out;
        }
        *bp = b;
        b = NULL; /* transferred */
        /* success */
        r = 0;
 out:
        oerrno = errno;
        sshbuf_free(b);
        ssh_digest_free(ctx);
        explicit_bzero(hash, sizeof(hash));
        errno = oerrno;
        return r;
}

int
sshsig_sign_fd(struct sshkey *key, const char *hashalg,
    const char *sk_provider, const char *sk_pin,
    int fd, const char *sig_namespace, struct sshbuf **out,
    sshsig_signer *signer, void *signer_ctx)
{
        struct sshbuf *b = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;

        if (hashalg == NULL)
                hashalg = HASHALG_DEFAULT;
        if (out != NULL)
                *out = NULL;
        if ((r = hash_file(fd, hashalg, &b)) != 0) {
                error_fr(r, "hash_file");
                return r;
        }
        if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b,
            sig_namespace, out, signer, signer_ctx)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        return r;
}

int
sshsig_verify_fd(struct sshbuf *signature, int fd,
    const char *expect_namespace, struct sshkey **sign_keyp,
    struct sshkey_sig_details **sig_details)
{
        struct sshbuf *b = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;
        char *hashalg = NULL;

        if (sig_details != NULL)
                *sig_details = NULL;
        if (sign_keyp != NULL)
                *sign_keyp = NULL;
        if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
                return r;
        debug_f("signature made with hash \"%s\"", hashalg);
        if ((r = hash_file(fd, hashalg, &b)) != 0) {
                error_fr(r, "hash_file");
                goto out;
        }
        if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
            sign_keyp, sig_details)) != 0)
                goto out;
        /* success */
        r = 0;
 out:
        sshbuf_free(b);
        free(hashalg);
        return r;
}

struct sshsigopt {
        int ca;
        char *namespaces;
        uint64_t valid_after, valid_before;
};

struct sshsigopt *
sshsigopt_parse(const char *opts, const char *path, u_long linenum,
    const char **errstrp)
{
        struct sshsigopt *ret;
        int r;
        char *opt;
        const char *errstr = NULL;

        if ((ret = calloc(1, sizeof(*ret))) == NULL)
                return NULL;
        if (opts == NULL || *opts == '\0')
                return ret; /* Empty options yields empty options :) */

        while (*opts && *opts != ' ' && *opts != '\t') {
                /* flag options */
                if ((r = opt_flag("cert-authority", 0, &opts)) != -1) {
                        ret->ca = 1;
                } else if (opt_match(&opts, "namespaces")) {
                        if (ret->namespaces != NULL) {
                                errstr = "multiple \"namespaces\" clauses";
                                goto fail;
                        }
                        ret->namespaces = opt_dequote(&opts, &errstr);
                        if (ret->namespaces == NULL)
                                goto fail;
                } else if (opt_match(&opts, "valid-after")) {
                        if (ret->valid_after != 0) {
                                errstr = "multiple \"valid-after\" clauses";
                                goto fail;
                        }
                        if ((opt = opt_dequote(&opts, &errstr)) == NULL)
                                goto fail;
                        if (parse_absolute_time(opt, &ret->valid_after) != 0 ||
                            ret->valid_after == 0) {
                                free(opt);
                                errstr = "invalid \"valid-after\" time";
                                goto fail;
                        }
                        free(opt);
                } else if (opt_match(&opts, "valid-before")) {
                        if (ret->valid_before != 0) {
                                errstr = "multiple \"valid-before\" clauses";
                                goto fail;
                        }
                        if ((opt = opt_dequote(&opts, &errstr)) == NULL)
                                goto fail;
                        if (parse_absolute_time(opt, &ret->valid_before) != 0 ||
                            ret->valid_before == 0) {
                                free(opt);
                                errstr = "invalid \"valid-before\" time";
                                goto fail;
                        }
                        free(opt);
                }
                /*
                 * Skip the comma, and move to the next option
                 * (or break out if there are no more).
                 */
                if (*opts == '\0' || *opts == ' ' || *opts == '\t')
                        break;          /* End of options. */
                /* Anything other than a comma is an unknown option */
                if (*opts != ',') {
                        errstr = "unknown key option";
                        goto fail;
                }
                opts++;
                if (*opts == '\0') {
                        errstr = "unexpected end-of-options";
                        goto fail;
                }
        }
        /* final consistency check */
        if (ret->valid_after != 0 && ret->valid_before != 0 &&
            ret->valid_before <= ret->valid_after) {
                errstr = "\"valid-before\" time is before \"valid-after\"";
                goto fail;
        }
        /* success */
        return ret;
 fail:
        if (errstrp != NULL)
                *errstrp = errstr;
        sshsigopt_free(ret);
        return NULL;
}

void
sshsigopt_free(struct sshsigopt *opts)
{
        if (opts == NULL)
                return;
        free(opts->namespaces);
        free(opts);
}

static int
parse_principals_key_and_options(const char *path, u_long linenum, char *line,
    const char *required_principal, char **principalsp, struct sshkey **keyp,
    struct sshsigopt **sigoptsp)
{
        char *opts = NULL, *tmp, *cp, *principals = NULL;
        const char *reason = NULL;
        struct sshsigopt *sigopts = NULL;
        struct sshkey *key = NULL;
        int r = SSH_ERR_INTERNAL_ERROR;

        if (principalsp != NULL)
                *principalsp = NULL;
        if (sigoptsp != NULL)
                *sigoptsp = NULL;
        if (keyp != NULL)
                *keyp = NULL;

        cp = line;
        cp = cp + strspn(cp, " \t\n\r"); /* skip leading whitespace */
        if (*cp == '#' || *cp == '\0')
                return SSH_ERR_KEY_NOT_FOUND; /* blank or all-comment line */

        /* format: identity[,identity...] [option[,option...]] key */
        if ((tmp = strdelimw(&cp)) == NULL || cp == NULL) {
                error("%s:%lu: invalid line", path, linenum);
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        if ((principals = strdup(tmp)) == NULL) {
                error_f("strdup failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        /*
         * Bail out early if we're looking for a particular principal and this
         * line does not list it.
         */
        if (required_principal != NULL) {
                if (match_pattern_list(required_principal,
                    principals, 0) != 1) {
                        /* principal didn't match */
                        r = SSH_ERR_KEY_NOT_FOUND;
                        goto out;
                }
                debug_f("%s:%lu: matched principal \"%s\"",
                    path, linenum, required_principal);
        }

        if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
                error_f("sshkey_new failed");
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        if (sshkey_read(key, &cp) != 0) {
                /* no key? Check for options */
                opts = cp;
                if (sshkey_advance_past_options(&cp) != 0) {
                        error("%s:%lu: invalid options", path, linenum);
                        r = SSH_ERR_INVALID_FORMAT;
                        goto out;
                }
                if (cp == NULL || *cp == '\0') {
                        error("%s:%lu: missing key", path, linenum);
                        r = SSH_ERR_INVALID_FORMAT;
                        goto out;
                }
                *cp++ = '\0';
                skip_space(&cp);
                if (sshkey_read(key, &cp) != 0) {
                        error("%s:%lu: invalid key", path, linenum);
                        r = SSH_ERR_INVALID_FORMAT;
                        goto out;
                }
        }
        debug3("%s:%lu: options %s", path, linenum, opts == NULL ? "" : opts);
        if ((sigopts = sshsigopt_parse(opts, path, linenum, &reason)) == NULL) {
                error("%s:%lu: bad options: %s", path, linenum, reason);
                r = SSH_ERR_INVALID_FORMAT;
                goto out;
        }
        /* success */
        if (principalsp != NULL) {
                *principalsp = principals;
                principals = NULL; /* transferred */
        }
        if (sigoptsp != NULL) {
                *sigoptsp = sigopts;
                sigopts = NULL; /* transferred */
        }
        if (keyp != NULL) {
                *keyp = key;
                key = NULL; /* transferred */
        }
        r = 0;
 out:
        free(principals);
        sshsigopt_free(sigopts);
        sshkey_free(key);
        return r;
}

static int
cert_filter_principals(const char *path, u_long linenum,
    char **principalsp, const struct sshkey *cert, uint64_t verify_time)
{
        char *cp, *oprincipals, *principals;
        const char *reason;
        struct sshbuf *nprincipals;
        int r = SSH_ERR_INTERNAL_ERROR, success = 0;
        u_int i;

        oprincipals = principals = *principalsp;
        *principalsp = NULL;

        if ((nprincipals = sshbuf_new()) == NULL) {
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }

        while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') {
                /* Check certificate validity */
                if ((r = sshkey_cert_check_authority(cert, 0, 1, 0,
                    verify_time, NULL, &reason)) != 0) {
                        debug("%s:%lu: principal \"%s\" not authorized: %s",
                            path, linenum, cp, reason);
                        continue;
                }
                /* Return all matching principal names from the cert */
                for (i = 0; i < cert->cert->nprincipals; i++) {
                        if (match_pattern(cert->cert->principals[i], cp)) {
                                if ((r = sshbuf_putf(nprincipals, "%s%s",
                                        sshbuf_len(nprincipals) != 0 ? "," : "",
                                                cert->cert->principals[i])) != 0) {
                                        error_f("buffer error");
                                        goto out;
                                }
                        }
                }
        }
        if (sshbuf_len(nprincipals) == 0) {
                error("%s:%lu: no valid principals found", path, linenum);
                r = SSH_ERR_KEY_CERT_INVALID;
                goto out;
        }
        if ((principals = sshbuf_dup_string(nprincipals)) == NULL) {
                error_f("buffer error");
                r = SSH_ERR_ALLOC_FAIL;
                goto out;
        }
        /* success */
        success = 1;
        *principalsp = principals;
 out:
        sshbuf_free(nprincipals);
        free(oprincipals);
        return success ? 0 : r;
}

static int
check_allowed_keys_line(const char *path, u_long linenum, char *line,
    const struct sshkey *sign_key, const char *principal,
    const char *sig_namespace, uint64_t verify_time, char **principalsp)
{
        struct sshkey *found_key = NULL;
        char *principals = NULL;
        int r, success = 0;
        const char *reason = NULL;
        struct sshsigopt *sigopts = NULL;
        char tvalid[64], tverify[64];

        if (principalsp != NULL)
                *principalsp = NULL;

        /* Parse the line */
        if ((r = parse_principals_key_and_options(path, linenum, line,
            principal, &principals, &found_key, &sigopts)) != 0) {
                /* error already logged */
                goto done;
        }

        if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
                /* Exact match of key */
                debug("%s:%lu: matched key", path, linenum);
        } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
            sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
                if (principal) {
                        /* Match certificate CA key with specified principal */
                        if ((r = sshkey_cert_check_authority(sign_key, 0, 1, 0,
                            verify_time, principal, &reason)) != 0) {
                                error("%s:%lu: certificate not authorized: %s",
                                    path, linenum, reason);
                                goto done;
                        }
                        debug("%s:%lu: matched certificate CA key",
                            path, linenum);
                } else {
                        /* No principal specified - find all matching ones */
                        if ((r = cert_filter_principals(path, linenum,
                            &principals, sign_key, verify_time)) != 0) {
                                /* error already displayed */
                                debug_r(r, "%s:%lu: cert_filter_principals",
                                    path, linenum);
                                goto done;
                        }
                        debug("%s:%lu: matched certificate CA key",
                            path, linenum);
                }
        } else {
                /* Didn't match key */
                goto done;
        }

        /* Check whether options preclude the use of this key */
        if (sigopts->namespaces != NULL && sig_namespace != NULL &&
            match_pattern_list(sig_namespace, sigopts->namespaces, 0) != 1) {
                error("%s:%lu: key is not permitted for use in signature "
                    "namespace \"%s\"", path, linenum, sig_namespace);
                goto done;
        }

        /* check key time validity */
        format_absolute_time((uint64_t)verify_time, tverify, sizeof(tverify));
        if (sigopts->valid_after != 0 &&
            (uint64_t)verify_time < sigopts->valid_after) {
                format_absolute_time(sigopts->valid_after,
                    tvalid, sizeof(tvalid));
                error("%s:%lu: key is not yet valid: "
                    "verify time %s < valid-after %s", path, linenum,
                    tverify, tvalid);
                goto done;
        }
        if (sigopts->valid_before != 0 &&
            (uint64_t)verify_time > sigopts->valid_before) {
                format_absolute_time(sigopts->valid_before,
                    tvalid, sizeof(tvalid));
                error("%s:%lu: key has expired: "
                    "verify time %s > valid-before %s", path, linenum,
                    tverify, tvalid);
                goto done;
        }
        success = 1;

 done:
        if (success && principalsp != NULL) {
                *principalsp = principals;
                principals = NULL; /* transferred */
        }
        free(principals);
        sshkey_free(found_key);
        sshsigopt_free(sigopts);
        return success ? 0 : SSH_ERR_KEY_NOT_FOUND;
}

int
sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key,
    const char *principal, const char *sig_namespace, uint64_t verify_time)
{
        FILE *f = NULL;
        char *line = NULL;
        size_t linesize = 0;
        u_long linenum = 0;
        int r = SSH_ERR_KEY_NOT_FOUND, oerrno;

        /* Check key and principal against file */
        if ((f = fopen(path, "r")) == NULL) {
                oerrno = errno;
                error("Unable to open allowed keys file \"%s\": %s",
                    path, strerror(errno));
                errno = oerrno;
                return SSH_ERR_SYSTEM_ERROR;
        }

        while (getline(&line, &linesize, f) != -1) {
                linenum++;
                r = check_allowed_keys_line(path, linenum, line, sign_key,
                    principal, sig_namespace, verify_time, NULL);
                free(line);
                line = NULL;
                linesize = 0;
                if (r == SSH_ERR_KEY_NOT_FOUND)
                        continue;
                else if (r == 0) {
                        /* success */
                        fclose(f);
                        return 0;
                } else
                        break;
        }
        /* Either we hit an error parsing or we simply didn't find the key */
        fclose(f);
        free(line);
        return r;
}

int
sshsig_find_principals(const char *path, const struct sshkey *sign_key,
    uint64_t verify_time, char **principals)
{
        FILE *f = NULL;
        char *line = NULL;
        size_t linesize = 0;
        u_long linenum = 0;
        int r = SSH_ERR_KEY_NOT_FOUND, oerrno;

        if ((f = fopen(path, "r")) == NULL) {
                oerrno = errno;
                error("Unable to open allowed keys file \"%s\": %s",
                    path, strerror(errno));
                errno = oerrno;
                return SSH_ERR_SYSTEM_ERROR;
        }

        while (getline(&line, &linesize, f) != -1) {
                linenum++;
                r = check_allowed_keys_line(path, linenum, line,
                    sign_key, NULL, NULL, verify_time, principals);
                free(line);
                line = NULL;
                linesize = 0;
                if (r == SSH_ERR_KEY_NOT_FOUND)
                        continue;
                else if (r == 0) {
                        /* success */
                        fclose(f);
                        return 0;
                } else
                        break;
        }
        free(line);
        /* Either we hit an error parsing or we simply didn't find the key */
        if (ferror(f) != 0) {
                oerrno = errno;
                fclose(f);
                error("Unable to read allowed keys file \"%s\": %s",
                    path, strerror(errno));
                errno = oerrno;
                return SSH_ERR_SYSTEM_ERROR;
        }
        fclose(f);
        return r;
}

int
sshsig_match_principals(const char *path, const char *principal,
    char ***principalsp, size_t *nprincipalsp)
{
        FILE *f = NULL;
        char *found, *line = NULL, **principals = NULL, **tmp;
        size_t i, nprincipals = 0, linesize = 0;
        u_long linenum = 0;
        int oerrno = 0, r, ret = 0;

        if (principalsp != NULL)
                *principalsp = NULL;
        if (nprincipalsp != NULL)
                *nprincipalsp = 0;

        /* Check key and principal against file */
        if ((f = fopen(path, "r")) == NULL) {
                oerrno = errno;
                error("Unable to open allowed keys file \"%s\": %s",
                    path, strerror(errno));
                errno = oerrno;
                return SSH_ERR_SYSTEM_ERROR;
        }

        while (getline(&line, &linesize, f) != -1) {
                linenum++;
                /* Parse the line */
                if ((r = parse_principals_key_and_options(path, linenum, line,
                    principal, &found, NULL, NULL)) != 0) {
                        if (r == SSH_ERR_KEY_NOT_FOUND)
                                continue;
                        ret = r;
                        oerrno = errno;
                        break; /* unexpected error */
                }
                if ((tmp = recallocarray(principals, nprincipals,
                    nprincipals + 1, sizeof(*principals))) == NULL) {
                        ret = SSH_ERR_ALLOC_FAIL;
                        free(found);
                        break;
                }
                principals = tmp;
                principals[nprincipals++] = found; /* transferred */
                free(line);
                line = NULL;
                linesize = 0;
        }
        fclose(f);

        if (ret == 0) {
                if (nprincipals == 0)
                        ret = SSH_ERR_KEY_NOT_FOUND;
                if (nprincipalsp != 0)
                        *nprincipalsp = nprincipals;
                if (principalsp != NULL) {
                        *principalsp = principals;
                        principals = NULL; /* transferred */
                        nprincipals = 0;
                }
        }

        for (i = 0; i < nprincipals; i++)
                free(principals[i]);
        free(principals);

        errno = oerrno;
        return ret;
}

int
sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey)
{
        struct sshkey *pk = NULL;
        int r = SSH_ERR_SIGNATURE_INVALID;

        if (pubkey == NULL)
                return SSH_ERR_INTERNAL_ERROR;
        if ((r = sshsig_parse_preamble(signature)) != 0)
                return r;
        if ((r = sshkey_froms(signature, &pk)) != 0)
                return r;

        *pubkey = pk;
        pk = NULL;
        return 0;
}