Add FFC param/key generation

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10909)

4 files changed, 1064 insertions, 1 deletions

diff --git a/crypto/ffc/build.info b/crypto/ffc/build.info
index 154d3c2510..d3314c30d1 100644
--- a/crypto/ffc/build.info
+++ b/crypto/ffc/build.info
@@ -1,6 +1,6 @@
 LIBS=../../libcrypto
 
-$COMMON=ffc_params.c
+$COMMON=ffc_params.c ffc_params_generate.c ffc_key_generate.c
 
 SOURCE[../../libcrypto]=$COMMON
 SOURCE[../../providers/libfips.a]=$COMMON
diff --git a/crypto/ffc/ffc_key_generate.c b/crypto/ffc/ffc_key_generate.c
new file mode 100644
index 0000000000..186245cc87
--- /dev/null
+++ b/crypto/ffc/ffc_key_generate.c
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include "internal/ffc.h"
+
+/*
+ * SP800-56Ar3 5.6.1.1.4 Key pair generation by testing candidates.
+ * Generates a private key in the interval [1, min(2 ^ N - 1, q - 1)].
+ *
+ * ctx must be set up with a libctx (for fips mode).
+ * params contains the FFC domain parameters p, q and g (for DH or DSA).
+ * N is the maximum bit length of the generated private key,
+ * s is the security strength.
+ * priv_key is the returned private key,
+ */
+int ffc_generate_private_key(BN_CTX *ctx, const FFC_PARAMS *params,
+                             int N, int s, BIGNUM *priv)
+{
+#ifdef FIPS_MODE
+    int ret = 0;
+    BIGNUM *m, *two_powN = NULL;
+
+    /* Step (2) : check range of N */
+    if (N < 2 * s || N > BN_num_bits(params->q))
+        return 0;
+
+    two_powN = BN_new();
+    /* 2^N */
+    if (two_powN == NULL || !BN_lshift(two_powN, BN_value_one(), N))
+        goto err;
+
+    /* Step (5) : M = min(2 ^ N, q) */
+    m = (BN_cmp(two_powN, params->q) > 0) ? params->q : two_powN;
+    do {
+        /* Steps (3, 4 & 7) :  c + 1 = 1 + random[0..2^N - 1] */
+        if (!BN_priv_rand_range_ex(priv, two_powN, ctx)
+            || !BN_add_word(priv, 1))
+            goto err;
+        /* Step (6) : loop if c > M - 2 (i.e. c + 1 >= M) */
+        if (BN_cmp(priv, m) < 0)
+            break;
+    } while (1);
+
+    ret = 1;
+err:
+    BN_free(two_powN);
+    return ret;
+#else
+    do {
+        if (!BN_priv_rand_range_ex(priv, params->q, ctx))
+            return 0;
+    } while (BN_is_zero(priv) || BN_is_one(priv));
+    return 1;
+#endif /* FIPS_MODE */
+}
diff --git a/crypto/ffc/ffc_params.c b/crypto/ffc/ffc_params.c
index 838ace3827..0c9d1a5d39 100644
--- a/crypto/ffc/ffc_params.c
+++ b/crypto/ffc/ffc_params.c
@@ -17,6 +17,7 @@ void ffc_params_init(FFC_PARAMS *params)
 {
     memset(params, 0, sizeof(FFC_PARAMS));
     params->pcounter = -1;
+    params->gindex = FFC_UNVERIFIABLE_GINDEX;
 }
 
 void ffc_params_cleanup(FFC_PARAMS *params)
diff --git a/crypto/ffc/ffc_params_generate.c b/crypto/ffc/ffc_params_generate.c
new file mode 100644
index 0000000000..c32c33e8b8
--- /dev/null
+++ b/crypto/ffc/ffc_params_generate.c
@@ -0,0 +1,1001 @@
+/*
+ * Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+/*
+ * For the prime check..
+ * FIPS 186-4 Section C.3 Table C.1
+ * Returns the minimum number of Miller Rabin iterations for a L,N pair
+ * (where L = len(p), N = len(q))
+ *   L   N                Min
+ * 1024  160              40
+ * 2048  224              56
+ * 2048  256              56
+ * 3072  256              64
+ *
+ * BN_check_prime() uses:
+ *  64 iterations for L <= 2048 OR
+ * 128 iterations for L > 2048
+ * So this satisfies the requirement.
+ */
+
+#include <string.h> /* memset */
+#include <openssl/sha.h> /* SHA_DIGEST_LENGTH */
+#include <openssl/rand.h>
+#include "crypto/bn.h"
+#include "internal/ffc.h"
+
+/*
+ * Verify that the passed in L, N pair for DH or DSA is valid.
+ * Returns 0 if invalid, otherwise it returns the security strength.
+ */
+static int ffc_validate_LN(size_t L, size_t N, int type)
+{
+    if (type == FFC_PARAM_TYPE_DH) {
+        /* Valid DH L,N parameters from SP800-56Ar3 5.5.1 Table 1 */
+        if (L == 2048 && (N == 224 || N == 256))
+            return 112;
+    } else if (type == FFC_PARAM_TYPE_DSA) {
+        /* Valid DSA L,N parameters from FIPS 186-4 Section 4.2 */
+        if (L == 1024 && N == 160)
+            return 80;
+        if (L == 2048 && (N == 224 || N == 256))
+            return 112;
+        if (L == 2048 && N == 256)
+            return 112;
+        if (L == 3072 && N == 256)
+            return 128;
+    }
+    return 0;
+}
+
+/* FIPS186-4 A.2.1 Unverifiable Generation of Generator g */
+static int generate_unverifiable_g(BN_CTX *ctx, BN_MONT_CTX *mont, BIGNUM *g,
+                                   BIGNUM *hbn, const BIGNUM *p,
+                                   const BIGNUM *e,const BIGNUM *pm1,
+                                   int *hret)
+{
+    int h = 2;
+
+    /* Step (2): choose h (where 1 < h)*/
+    if (!BN_set_word(hbn, h))
+        return 0;
+
+    for (;;) {
+        /* Step (3): g = h^e % p */
+        if (!BN_mod_exp_mont(g, hbn, e, p, ctx, mont))
+            return 0;
+        /* Step (4): Finish if g > 1 */
+        if (BN_cmp(g, BN_value_one()) > 0)
+            break;
+
+        /* Step (2) Choose any h in the range 1 < h < (p-1) */
+        if (!BN_add_word(hbn, 1) || BN_cmp(hbn, pm1) >= 0)
+            return 0;
+        ++h;
+    }
+    *hret = h;
+    return 1;
+}
+
+/*
+ * FIPS186-4 A.2 Generation of canonical generator g.
+ *
+ * It requires the following values as input:
+ *   'evpmd' digest, 'p' prime, 'e' cofactor, gindex and seed.
+ * tmp is a passed in temporary BIGNUM.
+ * mont is used in a BN_mod_exp_mont() with a modulus of p.
+ * Returns a value in g.
+ */
+static int generate_canonical_g(BN_CTX *ctx, BN_MONT_CTX *mont,
+                                const EVP_MD *evpmd, BIGNUM *g, BIGNUM *tmp,
+                                const BIGNUM *p, const BIGNUM *e,
+                                int gindex, unsigned char *seed, size_t seedlen)
+{
+    int ret = 0;
+    int counter = 1;
+    unsigned char md[EVP_MAX_MD_SIZE];
+    EVP_MD_CTX *mctx = NULL;
+    int mdsize;
+
+    mctx = EVP_MD_CTX_new();
+    if (mctx == NULL)
+        goto err;
+
+    mdsize = EVP_MD_size(evpmd);
+    if (mdsize <= 0)
+        goto err;
+   /*
+    * A.2.3 Step (4) & (5)
+    * A.2.4 Step (6) & (7)
+    * counter = 0; counter += 1
+    */
+    for (counter = 1; counter <= 0xFFFF; ++counter) {
+        /*
+         * A.2.3 Step (7) & (8) & (9)
+         * A.2.4 Step (9) & (10) & (11)
+         * W = Hash(seed || "ggen" || index || counter)
+         * g = W^e % p
+         */
+        static const unsigned char ggen[4] = { 0x67, 0x67, 0x65, 0x6e };
+
+        md[0] = (unsigned char)(gindex & 0xff);
+        md[1] = (unsigned char)((counter >> 8) & 0xff);
+        md[2] = (unsigned char)(counter & 0xff);
+        if (!EVP_DigestInit_ex(mctx, evpmd, NULL)
+                || !EVP_DigestUpdate(mctx, seed, seedlen)
+                || !EVP_DigestUpdate(mctx, ggen, sizeof(ggen))
+                || !EVP_DigestUpdate(mctx, md, 3)
+                || !EVP_DigestFinal_ex(mctx, md, NULL)
+                || (BN_bin2bn(md, mdsize, tmp) == NULL)
+                || !BN_mod_exp_mont(g, tmp, e, p, ctx, mont))
+                    return 0;
+        /*
+         * A.2.3 Step (10)
+         * A.2.4 Step (12)
+         * Found a value for g if (g >= 2)
+         */
+        if (BN_cmp(g, BN_value_one()) > 0) {
+            ret = 1;
+            break; /* found g */
+        }
+    }
+err:
+    EVP_MD_CTX_free(mctx);
+    return ret;
+}
+
+/* Generation of p is the same for FIPS 186-4 & FIPS 186-2 */
+static int generate_p(BN_CTX *ctx, const EVP_MD *evpmd, int max_counter, int n,
+                      unsigned char *buf, size_t buf_len, const BIGNUM *q,
+                      BIGNUM *p, int L, BN_GENCB *cb, int *counter,
+                      int *res)
+{
+    int ret = -1;
+    int i, j, k, r;
+    unsigned char md[EVP_MAX_MD_SIZE];
+    int mdsize;
+    BIGNUM *W, *X, *tmp, *c, *test;
+
+    BN_CTX_start(ctx);
+    W = BN_CTX_get(ctx);
+    X = BN_CTX_get(ctx);
+    c = BN_CTX_get(ctx);
+    test = BN_CTX_get(ctx);
+    tmp = BN_CTX_get(ctx);
+    if (tmp == NULL)
+        goto err;
+
+    if (!BN_lshift(test, BN_value_one(), L - 1))
+        goto err;
+
+    mdsize = EVP_MD_size(evpmd);
+    if (mdsize <= 0)
+        goto err;
+
+    /* A.1.1.2 Step (10) AND
+     * A.1.1.2 Step (12)
+     * offset = 1 (this is handled below)
+     */
+    /*
+     * A.1.1.2 Step (11) AND
+     * A.1.1.3 Step (13)
+     */
+    for (i = 0; i <= max_counter; i++) {
+        if ((i != 0) && !BN_GENCB_call(cb, 0, i))
+            goto err;
+
+        BN_zero(W);
+        /* seed_tmp buffer contains "seed + offset - 1" */
+        for (j = 0; j <= n; j++) {
+            /* obtain "seed + offset + j" by incrementing by 1: */
+            for (k = (int)buf_len - 1; k >= 0; k--) {
+                buf[k]++;
+                if (buf[k] != 0)
+                    break;
+            }
+            /*
+             * A.1.1.2 Step (11.1) AND
+             * A.1.1.3 Step (13.1)
+             * tmp = V(j) = Hash((seed + offset + j) % 2^seedlen)
+             */
+            if (!EVP_Digest(buf, buf_len, md, NULL, evpmd, NULL)
+                    || (BN_bin2bn(md, mdsize, tmp) == NULL)
+                    /*
+                     * A.1.1.2 Step (11.2)
+                     * A.1.1.3 Step (13.2)
+                     * W += V(j) * 2^(outlen * j)
+                     */
+                    || !BN_lshift(tmp, tmp, (mdsize << 3) * j)
+                    || !BN_add(W, W, tmp))
+                goto err;
+        }
+
+        /*
+         * A.1.1.2 Step (11.3) AND
+         * A.1.1.3 Step (13.3)
+         * X = W + 2^(L-1) where W < 2^(L-1)
+         */
+        if (!BN_mask_bits(W, L - 1)
+                || !BN_copy(X, W)
+                || !BN_add(X, X, test)
+                /*
+                 * A.1.1.2 Step (11.4) AND
+                 * A.1.1.3 Step (13.4)
+                 * c = X mod 2q
+                 */
+                || !BN_lshift1(tmp, q)
+                || !BN_mod(c, X, tmp, ctx)
+                /*
+                 * A.1.1.2 Step (11.5) AND
+                 * A.1.1.3 Step (13.5)
+                 * p = X - (c - 1)
+                 */
+                || !BN_sub(tmp, c, BN_value_one())
+                || !BN_sub(p, X, tmp))
+            goto err;
+
+        /*
+         * A.1.1.2 Step (11.6) AND
+         * A.1.1.3 Step (13.6)
+         * if (p < 2 ^ (L-1)) continue
+         * This makes sure the top bit is set.
+         */
+        if (BN_cmp(p, test) >= 0) {
+            /*
+             * A.1.1.2 Step (11.7) AND
+             * A.1.1.3 Step (13.7)
+             * Test if p is prime
+             * (This also makes sure the bottom bit is set)
+             */
+            r = BN_check_prime(p, ctx, cb);
+            /* A.1.1.2 Step (11.8) : Return if p is prime */
+            if (r > 0) {
+                *counter = i;
+                ret = 1;   /* return success */
+                goto err;
+            }
+            if (r != 0)
+                goto err;
+        }
+        /* Step (11.9) : offset = offset + n + 1 is done auto-magically */
+    }
+    /* No prime P found */
+    ret = 0;
+    *res |= FFC_CHECK_P_NOT_PRIME;
+err:
+    BN_CTX_end(ctx);
+    return ret;
+}
+
+static int generate_q_fips186_4(BN_CTX *ctx, BIGNUM *q, const EVP_MD *evpmd,
+                                int qsize, unsigned char *seed, size_t seedlen,
+                                int generate_seed, int *retm, int *res,
+                                BN_GENCB *cb)
+{
+    int ret = 0, r;
+    int m = *retm;
+    unsigned char md[EVP_MAX_MD_SIZE];
+    int mdsize = EVP_MD_size(evpmd);
+    unsigned char *pmd;
+    OPENSSL_CTX *libctx = bn_get_lib_ctx(ctx);
+
+    /* find q */
+    for (;;) {
+        if(!BN_GENCB_call(cb, 0, m++))
+            goto err;
+
+        /* A.1.1.2 Step (5) : generate seed with size seed_len */
+        if (generate_seed
+                && RAND_bytes_ex(libctx, seed, (int)seedlen) < 0)
+            goto err;
+        /*
+         * A.1.1.2 Step (6) AND
+         * A.1.1.3 Step (7)
+         * U = Hash(seed) % (2^(N-1))
+         */
+        if (!EVP_Digest(seed, seedlen, md, NULL, evpmd, NULL))
+            goto err;
+        /* Take least significant bits of md */
+        if (mdsize > qsize)
+            pmd = md + mdsize - qsize;
+        else
+            pmd = md;
+        if (mdsize < qsize)
+            memset(md + mdsize, 0, qsize - mdsize);
+
+        /*
+         * A.1.1.2 Step (7) AND
+         * A.1.1.3 Step (8)
+         * q = U + 2^(N-1) + (1 - U %2) (This sets top and bottom bits)
+         */
+        pmd[0] |= 0x80;
+        pmd[qsize-1] |= 0x01;
+        if (!BN_bin2bn(pmd, qsize, q))
+            goto err;
+
+        /*
+         * A.1.1.2 Step (8) AND
+         * A.1.1.3 Step (9)
+         * Test if q is prime
+         */
+        r = BN_check_prime(q, ctx, cb);
+        if (r > 0) {
+            ret = 1;
+            goto err;
+        }
+        /*
+         * A.1.1.3 Step (9) : If the provided seed didn't produce a prime q
+         * return an error.
+         */
+        if (!generate_seed) {
+            *res |= FFC_CHECK_Q_NOT_PRIME;
+            goto err;
+        }
+        if (r != 0)
+            goto err;
+        /* A.1.1.2 Step (9) : if q is not prime, try another q */
+    }
+err:
+    *retm = m;
+    return ret;
+}
+
+static int generate_q_fips186_2(BN_CTX *ctx, BIGNUM *q, const EVP_MD *evpmd,
+                                unsigned char *buf, unsigned char *seed,
+                                size_t qsize, int generate_seed, int *retm,
+                                int *res, BN_GENCB *cb)
+{
+    unsigned char buf2[EVP_MAX_MD_SIZE];
+    unsigned char md[EVP_MAX_MD_SIZE];
+    int i, r, ret = 0, m = *retm;
+    OPENSSL_CTX *libctx = bn_get_lib_ctx(ctx);
+
+    /* find q */
+    for (;;) {
+        /* step 1 */
+        if (!BN_GENCB_call(cb, 0, m++))
+            goto err;
+
+        if (generate_seed && RAND_bytes_ex(libctx, seed, (int)qsize) <= 0)
+            goto err;
+
+        memcpy(buf, seed, qsize);
+        memcpy(buf2, seed, qsize);
+
+        /* precompute "SEED + 1" for step 7: */
+        for (i = (int)qsize - 1; i >= 0; i--) {
+            buf[i]++;
+            if (buf[i] != 0)
+                break;
+        }
+
+        /* step 2 */
+        if (!EVP_Digest(seed, qsize, md, NULL, evpmd, NULL))
+            goto err;
+        if (!EVP_Digest(buf, qsize, buf2, NULL, evpmd, NULL))
+            goto err;
+        for (i = 0; i < (int)qsize; i++)
+            md[i] ^= buf2[i];
+
+        /* step 3 */
+        md[0] |= 0x80;
+        md[qsize - 1] |= 0x01;
+        if (!BN_bin2bn(md, (int)qsize, q))
+            goto err;
+
+        /* step 4 */
+        r = BN_check_prime(q, ctx, cb);
+        if (r > 0) {
+            /* Found a prime */
+            ret = 1;
+            goto err;
+        }
+        if (r != 0)
+            goto err; /* Exit if error */
+        /* Try another iteration if it wasnt prime - was in old code.. */
+        generate_seed = 1;
+    }
+err:
+    *retm = m;
+    return ret;
+}
+
+static EVP_MD *fetch_default_md(OPENSSL_CTX *libctx, size_t N)
+{
+    char *name = NULL;
+
+    if (N == 160)
+        name = "SHA1";
+    else if (N == 224)
+        name = "SHA-224";
+    else if (N == 256)
+        name = "SHA-256";
+
+    return name !=  NULL ?  EVP_MD_fetch(libctx, name, "") : NULL;
+}
+
+/*
+ * FIPS 186-4 FFC parameter generation (as defined in Appendix A).
+ * The same code is used for validation (when validate_flags != 0)
+ *
+ * The primes p & q are generated/validated using:
+ *   A.1.1.2 Generation of probable primes p & q using approved hash.
+ *   A.1.1.3 Validation of generated probable primes
+ *
+ * Generator 'g' has 2 types in FIPS 186-4:
+ *   (1) A.2.1 unverifiable generation of generator g.
+ *       A.2.2 Assurance of the validity of unverifiable generator g.
+ *   (2) A.2.3 Verifiable Canonical Generation of the generator g.
+ *       A.2.4 Validation for Canonical Generation of the generator g.
+ *
+ * Notes:
+ * (1) is only a partial validation of g, The validation of (2) requires
+ * the seed and index used during generation as input.
+ *
+ * params: used to pass in values for generation and validation.
+ *  For generation of p & q:
+ *   - This is skipped if p & q are passed in.
+ *   - If the seed is passed in then generation of p & q uses this seed (and if
+ *     this fails an error will occur).
+ *   - Otherwise the seed is generated, and values of p & q are generated and
+ *     the value of seed and counter are optionally returned.
+ *  For the generation of g (after the generation of p, q):
+ *   - If the seed has been generated or passed in and a valid gindex is passed
+ *     in then canonical generation of g is used otherwise unverifiable
+ *     generation of g is chosen.
+ *  For validation of p & q:
+ *   - p, q, and the seed and counter used for generation must be passed in.
+ *  For validation of g:
+ *   - For a partial validation : p, q and g are required.
+ *   - For a canonical validation : the gindex and seed used for generation are
+ *     also required.
+ * type: The key type - FFC_PARAM_TYPE_DSA or FFC_PARAM_TYPE_DH.
+ * L: is the size of the prime p in bits (e.g 2048)
+ * N: is the size of the prime q in bits (e.g 256)
+ * evpmd: is the digest to use, If this value is NULL, then the digest is chosen
+ *        using the value of N.
+ * validate_flags:
+ *  or generation: FFC_PARAMS_GENERATE.
+ *  For validation one of:
+ *   -FFC_PARAMS_VALIDATE_PQ
+ *   -FFC_PARAMS_VALIDATE_G
+ *   -FFC_PARAMS_VALIDATE_ALL
+ * res: A returned failure reason (One of FFC_CHECK_XXXX),
+ *      or 0 for general failures.
+ * cb: A callback (can be NULL) that is called during different phases
+ *
+ * Returns:
+ *   - FFC_PARAMS_RET_STATUS_FAILED: if there was an error, or validation failed.
+ *   - FFC_PARAMS_RET_STATUS_SUCCESS if the generation or validation succeeded.
+ *   - FFC_PARAMS_RET_STATUS_UNVERIFIABLE_G if the validation of G succeeded,
+ *     but G is unverifiable.
+ */
+int ffc_param_FIPS186_4_gen_verify(OPENSSL_CTX *libctx, FFC_PARAMS *params,
+                                   int type, size_t L, size_t N,
+                                   const EVP_MD *evpmd, int validate_flags,
+                                   int *res, BN_GENCB *cb)
+{
+    int ok = FFC_PARAMS_RET_STATUS_FAILED;
+    unsigned char *seed = NULL, *seed_tmp = NULL;
+    int mdsize, counter = 0, pcounter = 0, r = 0;
+    size_t seedlen = 0;
+    BIGNUM *tmp, *pm1, *e, *test;
+    BIGNUM *g = NULL, *q = NULL, *p = NULL;
+    BN_MONT_CTX *mont = NULL;
+    int n = 0, m = 0, qsize = N >> 3;
+    int canonical_g = 0, hret = -1;
+    BN_CTX *ctx = NULL;
+    EVP_MD_CTX *mctx = NULL;
+    int generate = (validate_flags == 0);
+    EVP_MD *evpmd_fetch = NULL;
+
+    *res = 0;
+
+    /*
+     * A.1.1.2 Step (1) AND
+     * A.1.1.3 Step (3)
+     * Check that the L,N pair is an acceptable pair.
+     */
+    if (L <= N || !ffc_validate_LN(L, N, type)) {
+        *res = FFC_CHECK_BAD_LN_PAIR;
+        goto err;
+    }
+
+    mctx = EVP_MD_CTX_new();
+    if (mctx == NULL)
+        goto err;
+
+    if (evpmd == NULL) {
+        evpmd_fetch = fetch_default_md(libctx, N);
+        evpmd = evpmd_fetch;
+    }
+
+    mdsize = EVP_MD_size(evpmd);
+    if (mdsize <= 0)
+        goto err;
+
+    if ((ctx = BN_CTX_new_ex(libctx)) == NULL)
+        goto err;
+
+    BN_CTX_start(ctx);
+    g = BN_CTX_get(ctx);
+    pm1 = BN_CTX_get(ctx);
+    e = BN_CTX_get(ctx);
+    test = BN_CTX_get(ctx);
+    tmp = BN_CTX_get(ctx);
+    if (tmp == NULL)
+        goto err;
+
+    seedlen = params->seedlen;
+    if (seedlen == 0)
+        seedlen = (size_t)mdsize;
+    /* If the seed was passed in - use this value as the seed */
+    if (params->seed != NULL)
+        seed = params->seed;
+
+    if (generate) {
+        /* For generation: p & q must both be NULL or NON-NULL */
+        if ((params->p == NULL) != (params->q == NULL)) {
+            *res = FFC_CHECK_INVALID_PQ;
+            goto err;
+        }
+    } else {
+        /* Validation of p,q requires seed and counter to be valid */
+        if ((validate_flags & FFC_PARAMS_VALIDATE_PQ) != 0) {
+            if (seed == NULL || params->pcounter < 0) {
+                *res = FFC_CHECK_MISSING_SEED_OR_COUNTER;
+                goto err;
+            }
+        }
+        if ((validate_flags & FFC_PARAMS_VALIDATE_G) != 0) {
+            /* validation of g also requires g to be set */
+            if (params->g == NULL) {
+                *res = FFC_CHECK_INVALID_G;
+                goto err;
+            }
+        }
+    }
+
+    /*
+     * If p & q are passed in and
+     *   validate_flags = 0 then skip the generation of PQ.
+     *   validate_flags = VALIDATE_G then also skip the validation of PQ.
+     */
+    if (params->p != NULL && ((validate_flags & FFC_PARAMS_VALIDATE_PQ) == 0)) {
+        /* p and q already exists so only generate g */
+        p = params->p;
+        q = params->q;
+        goto g_only;
+        /* otherwise fall thru to validate p & q */
+    }
+
+    /* p & q will be used for generation and validation */
+    p = BN_CTX_get(ctx);
+    q = BN_CTX_get(ctx);
+    if (q == NULL)
+        goto err;
+
+    /*
+     * A.1.1.2 Step (2) AND
+     * A.1.1.3 Step (6)
+     * Return invalid if seedlen  < N
+     */
+    if ((seedlen * 8) < N) {
+        *res = FFC_CHECK_INVALID_SEED_SIZE;
+        goto err;
+    }
+
+    seed_tmp = OPENSSL_malloc(seedlen);
+    if (seed_tmp == NULL)
+        goto err;
+
+    if (seed == NULL) {
+        /* Validation requires the seed to be supplied */
+        if (validate_flags) {
+            *res = FFC_CHECK_MISSING_SEED_OR_COUNTER;
+            goto err;
+        }
+        /* if the seed is not supplied then alloc a seed buffer */
+        seed = OPENSSL_malloc(seedlen);
+        if (seed == NULL)
+            goto err;
+    }
+
+    /* A.1.1.2 Step (11): max loop count = 4L - 1 */
+    counter = 4 * L - 1;
+    /* Validation requires the counter to be supplied */
+    if (validate_flags) {
+        /* A.1.1.3 Step (4) : if (counter > (4L -1)) return INVALID */
+        if (params->pcounter > counter) {
+            *res = FFC_CHECK_INVALID_COUNTER;
+            goto err;
+        }
+        counter = params->pcounter;
+    }
+
+    /*
+     * A.1.1.2 Step (3) AND
+     * A.1.1.3 Step (10)
+     * n = floor(L / hash_outlen) - 1
+     */
+    n = (L - 1 ) / (mdsize << 3);
+
+    /* Calculate 2^(L-1): Used in step A.1.1.2 Step (11.3) */
+    if (!BN_lshift(test, BN_value_one(), L - 1))
+        goto err;
+
+    for (;;) {
+        if (!generate_q_fips186_4(ctx, q, evpmd, qsize, seed, seedlen,
+                                  seed != params->seed, &m, res, cb))
+            goto err;
+        /* A.1.1.3 Step (9): Verify that q matches the expected value */
+        if (validate_flags && (BN_cmp(q, params->q) != 0)) {
+            *res = FFC_CHECK_Q_MISMATCH;
+            goto err;
+        }
+        if(!BN_GENCB_call(cb, 2, 0))
+            goto err;
+        if(!BN_GENCB_call(cb, 3, 0))
+            goto err;
+
+        memcpy(seed_tmp, seed, seedlen);
+        r = generate_p(ctx, evpmd, counter, n, seed_tmp, seedlen, q, p, L, cb,
+                       &pcounter, res);
+        if (r > 0)
+            break; /* found p */
+        if (r < 0)
+            goto err;
+        /*
+         * A.1.1.3 Step (14):
+         * If we get here we failed to get a p for the given seed. If the
+         * seed is not random then it needs to fail (as it will always fail).
+         */
+        if (seed == params->seed) {
+            *res = FFC_CHECK_P_NOT_PRIME;
+            goto err;
+        }
+    }
+    if(!BN_GENCB_call(cb, 2, 1))
+        goto err;
+    /*
+     * Gets here if we found p.
+     * A.1.1.3 Step (14): return error if i != counter OR computed_p != known_p.
+     */
+    if (validate_flags && (pcounter != counter || (BN_cmp(p, params->p) != 0)))
+        goto err;
+
+    /* If validating p & q only then skip the g validation test */
+    if ((validate_flags & FFC_PARAMS_VALIDATE_ALL) == FFC_PARAMS_VALIDATE_PQ)
+        goto pass;
+g_only:
+    if ((mont = BN_MONT_CTX_new()) == NULL)
+        goto err;
+    if (!BN_MONT_CTX_set(mont, p, ctx))
+        goto err;
+
+    if (((validate_flags & FFC_PARAMS_VALIDATE_G) != 0)
+        && !ffc_params_validate_unverifiable_g(ctx, mont, p, q, params->g,
+                                               tmp, res))
+        goto err;
+
+    /*
+     * A.2.1 Step (1) AND
+     * A.2.3 Step (3) AND
+     * A.2.4 Step (5)
+     * e = (p - 1) / q (i.e- Cofactor 'e' is given by p = q * e + 1)
+     */
+    if (!(BN_sub(pm1, p, BN_value_one()) && BN_div(e, NULL, pm1, q, ctx)))
+        goto err;
+
+    /* Canonical g requires a seed and index to be set */
+    if ((seed != NULL) && (params->gindex != FFC_UNVERIFIABLE_GINDEX)) {
+        canonical_g = 1;
+        if (!generate_canonical_g(ctx, mont, evpmd, g, tmp, p, e,
+                                  params->gindex, seed, seedlen)) {
+            *res = FFC_CHECK_INVALID_G;
+            goto err;
+        }
+        /* A.2.4 Step (13): Return valid if computed_g == g */
+        if (validate_flags && BN_cmp(g, params->g) != 0) {
+            *res = FFC_CHECK_G_MISMATCH;
+            goto err;
+        }
+    } else if (generate) {
+        if (!generate_unverifiable_g(ctx, mont, g, tmp, p, e, pm1, &hret))
+            goto err;
+    }
+
+    if (!BN_GENCB_call(cb, 3, 1))
+        goto err;
+
+    if (generate) {
+        if (p != params->p) {
+            BN_free(params->p);
+            params->p = BN_dup(p);
+        }
+        if (q != params->q) {
+            BN_free(params->q);
+            params->q = BN_dup(q);
+        }
+        if (g != params->g) {
+            BN_free(params->g);
+            params->g = BN_dup(g);
+        }
+        if (params->p == NULL || params->q == NULL || params->g == NULL)
+            goto err;
+        if (!ffc_params_set_validate_params(params, seed, seedlen, pcounter))
+            goto err;
+        params->h = hret;
+    }
+pass:
+    if ((validate_flags & FFC_PARAMS_VALIDATE_G) != 0 && (canonical_g == 0))
+        /* Return for the case where g is partially valid */
+        ok = FFC_PARAMS_RET_STATUS_UNVERIFIABLE_G;
+    else
+        ok = FFC_PARAMS_RET_STATUS_SUCCESS;
+err:
+    if (seed != params->seed)
+        OPENSSL_free(seed);
+    OPENSSL_free(seed_tmp);
+    if (ctx)
+        BN_CTX_end(ctx);
+    BN_CTX_free(ctx);
+    BN_MONT_CTX_free(mont);
+    EVP_MD_free(evpmd_fetch);
+    EVP_MD_CTX_free(mctx);
+    return ok;
+}
+
+int ffc_param_FIPS186_2_gen_verify(OPENSSL_CTX *libctx, FFC_PARAMS *params,
+                                   int type, size_t L, size_t N,
+                                   const EVP_MD *evpmd, int validate_flags,
+                                   int *res, BN_GENCB *cb)
+{
+    int ok = FFC_PARAMS_RET_STATUS_FAILED;
+    unsigned char seed[SHA256_DIGEST_LENGTH];
+    unsigned char buf[SHA256_DIGEST_LENGTH];
+    BIGNUM *r0, *test, *tmp, *g = NULL, *q = NULL, *p = NULL;
+    BN_MONT_CTX *mont = NULL;
+    size_t qsize = N >> 3;
+    int n = 0, m = 0;
+    int counter = 0, pcounter = 0, use_random_seed;
+    int rv;
+    BN_CTX *ctx = NULL;
+    int hret = -1;
+    int generate = (validate_flags == 0);
+    unsigned char *seed_in = params->seed;
+    size_t seed_len = params->seedlen;
+    EVP_MD *evpmd_fetch = NULL;
+
+    *res = 0;
+#ifdef FIPS_MODE
+    /*
+     * FIPS 186-4 states that validation can only be done for this pair.
+     * (Even though the original spec allowed L = 512 + 64*j (j = 0.. 8))
+     */
+    if (L != 1024 || N != 160) {
+        *res = FFC_CHECK_BAD_LN_PAIR;
+        return FFC_PARAMS_RET_STATUS_FAILED;
+    }
+#endif
+    if (qsize != SHA_DIGEST_LENGTH
+        && qsize != SHA224_DIGEST_LENGTH
+        && qsize != SHA256_DIGEST_LENGTH) {
+        /* invalid q size */
+        *res = FFC_CHECK_INVALID_Q_VALUE;
+        return FFC_PARAMS_RET_STATUS_FAILED;
+    }
+
+    if (evpmd == NULL) {
+        evpmd_fetch = fetch_default_md(libctx, qsize * 8);
+        evpmd = evpmd_fetch;
+    } else {
+        rv = EVP_MD_size(evpmd);
+        if (rv <= 0)
+            return 0;
+        qsize = (size_t)rv;
+    }
+
+    if (L < 512)
+        L = 512;
+
+    L = (L + 63) / 64 * 64;
+
+    if (seed_in != NULL) {
+        if (seed_len < qsize) {
+            *res = FFC_CHECK_INVALID_SEED_SIZE;
+            return 0;
+        }
+        if (seed_len > qsize) {
+            /* Only consume as much seed as is expected. */
+            seed_len = qsize;
+        }
+        memcpy(seed, seed_in, seed_len);
+    }
+
+    ctx = BN_CTX_new_ex(libctx);
+    if (ctx == NULL)
+        goto err;
+
+    BN_CTX_start(ctx);
+
+    r0 = BN_CTX_get(ctx);
+    g = BN_CTX_get(ctx);
+    q = BN_CTX_get(ctx);
+    p = BN_CTX_get(ctx);
+    tmp = BN_CTX_get(ctx);
+    test = BN_CTX_get(ctx);
+    if (test == NULL)
+        goto err;
+
+    if (!BN_lshift(test, BN_value_one(), L - 1))
+        goto err;
+
+    if (generate) {
+        /* For generation: p & q must both be NULL or NON-NULL */
+        if ((params->p != NULL) != (params->q != NULL)) {
+            *res = FFC_CHECK_INVALID_PQ;
+            goto err;
+        }
+    } else {
+        if ((validate_flags & FFC_PARAMS_VALIDATE_PQ) != 0) {
+            /* Validation of p,q requires seed and counter to be valid */
+            if (seed_in == NULL || params->pcounter < 0) {
+                *res = FFC_CHECK_MISSING_SEED_OR_COUNTER;
+                goto err;
+            }
+        }
+        if ((validate_flags & FFC_PARAMS_VALIDATE_G) != 0) {
+            /* validation of g also requires g to be set */
+            if (params->g == NULL) {
+                *res = FFC_CHECK_INVALID_G;
+                goto err;
+            }
+        }
+    }
+
+    if (params->p != NULL && ((validate_flags & FFC_PARAMS_VALIDATE_PQ) == 0)) {
+        /* p and q already exists so only generate g */
+        p = params->p;
+        q = params->q;
+        goto g_only;
+        /* otherwise fall thru to validate p and q */
+    }
+
+    use_random_seed = (seed_in == NULL);
+    for (;;) {
+        if (!generate_q_fips186_2(ctx, q, evpmd, buf, seed, qsize,
+                                  use_random_seed, &m, res, cb))
+            goto err;
+
+        if (!BN_GENCB_call(cb, 2, 0))
+            goto err;
+        if (!BN_GENCB_call(cb, 3, 0))
+            goto err;
+
+        /* step 6 */
+        n = (L - 1) / 160;
+        counter = 4 * L - 1; /* Was 4096 */
+        /* Validation requires the counter to be supplied */
+        if (validate_flags) {
+            if (params->pcounter > counter) {
+                *res = FFC_CHECK_INVALID_COUNTER;
+                goto err;
+            }
+            counter = params->pcounter;
+        }
+
+        rv = generate_p(ctx, evpmd, counter, n, buf, qsize, q, p, L, cb,
+                        &pcounter, res);
+        if (rv > 0)
+            break; /* found it */
+        if (rv == -1)
+            goto err;
+        /* This is what the old code did - probably not a good idea! */
+        use_random_seed = 1;
+    }
+
+    if (!BN_GENCB_call(cb, 2, 1))
+        goto err;
+
+    if (validate_flags) {
+        if (pcounter != counter) {
+            *res = FFC_CHECK_COUNTER_MISMATCH;
+            goto err;
+        }
+        if (BN_cmp(p, params->p) != 0) {
+            *res = FFC_CHECK_P_MISMATCH;
+            goto err;
+        }
+    }
+    /* If validating p & q only then skip the g validation test */
+    if ((validate_flags & FFC_PARAMS_VALIDATE_ALL) == FFC_PARAMS_VALIDATE_PQ)
+        goto pass;
+g_only:
+    if ((mont = BN_MONT_CTX_new()) == NULL)
+        goto err;
+    if (!BN_MONT_CTX_set(mont, p, ctx))
+        goto err;
+
+    if (generate) {
+        /* We now need to generate g */
+        /* set test = p - 1 */
+        if (!BN_sub(test, p, BN_value_one()))
+            goto err;
+        /* Set r0 = (p - 1) / q */
+        if (!BN_div(r0, NULL, test, q, ctx))
+            goto err;
+        if (!generate_unverifiable_g(ctx, mont, g, tmp, p, r0, test, &hret))
+            goto err;
+    } else if (((validate_flags & FFC_PARAMS_VALIDATE_G) != 0)
+               && !ffc_params_validate_unverifiable_g(ctx, mont, p, q,
+                                                      params->g, tmp, res)) {
+        goto err;
+    }
+
+    if (!BN_GENCB_call(cb, 3, 1))
+        goto err;
+
+    if (generate) {
+        if (p != params->p) {
+            BN_free(params->p);
+            params->p = BN_dup(p);
+        }
+        if (q != params->q) {
+            BN_free(params->q);
+            params->q = BN_dup(q);
+        }
+        if (g != params->g) {
+            BN_free(params->g);
+            params->g = BN_dup(g);
+        }
+        if (params->p == NULL || params->q == NULL || params->g == NULL)
+            goto err;
+        if (!ffc_params_set_validate_params(params, seed, qsize, pcounter))
+            goto err;
+        params->h = hret;
+    }
+pass:
+    if ((validate_flags & FFC_PARAMS_VALIDATE_G) != 0)
+        ok = FFC_PARAMS_RET_STATUS_UNVERIFIABLE_G;
+    else
+        ok = FFC_PARAMS_RET_STATUS_SUCCESS;
+err:
+    if (ctx != NULL)
+        BN_CTX_end(ctx);
+    BN_CTX_free(ctx);
+    EVP_MD_free(evpmd_fetch);
+    BN_MONT_CTX_free(mont);
+    return ok;
+}
+
+int ffc_params_FIPS186_4_generate(OPENSSL_CTX *libctx, FFC_PARAMS *params,
+                                  int type, size_t L, size_t N,
+                                  const EVP_MD *evpmd, int *res, BN_GENCB *cb)
+{
+    return ffc_param_FIPS186_4_gen_verify(libctx, params, type, L, N, evpmd, 0,
+                                          res, cb);
+}
+
+/* This should no longer be used in FIPS mode */
+int ffc_params_FIPS186_2_generate(OPENSSL_CTX *libctx, FFC_PARAMS *params,
+                                  int type, size_t L, size_t N,
+                                  const EVP_MD *evpmd, int *res, BN_GENCB *cb)
+{
+    return ffc_param_FIPS186_2_gen_verify(libctx, params, type, L, N, evpmd,
+                                          0, res, cb);
+}
+
+/* TODO(3.0) - Add this in another PR -  just add a stub for now */
+int ffc_params_validate_unverifiable_g(BN_CTX *ctx, BN_MONT_CTX *mont,
+                                       const BIGNUM *p, const BIGNUM *q,
+                                       const BIGNUM *g, BIGNUM *tmp, int *ret)
+{
+    return 1;
+}