OpenSSL 1.1.1-pre2

crypto/rsa/rsa_gen.c

@@ -19,7 +19,7 @@
 #include <openssl/bn.h>
 #include "rsa_locl.h"
 
-static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
+static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
                               BN_GENCB *cb);
 
 /*
@@ -31,29 +31,60 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
  */
 int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)
 {
-    if (rsa->meth->rsa_keygen)
+    if (rsa->meth->rsa_keygen != NULL)
         return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
-    return rsa_builtin_keygen(rsa, bits, e_value, cb);
+
+    return RSA_generate_multi_prime_key(rsa, bits, RSA_DEFAULT_PRIME_NUM,
+                                        e_value, cb);
 }
 
-static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
+int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,
+                                 BIGNUM *e_value, BN_GENCB *cb)
+{
+    /* multi-prime is only supported with the builtin key generation */
+    if (rsa->meth->rsa_multi_prime_keygen != NULL) {
+        return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,
+                                                 e_value, cb);
+    } else if (rsa->meth->rsa_keygen != NULL) {
+        /*
+         * However, if rsa->meth implements only rsa_keygen, then we
+         * have to honour it in 2-prime case and assume that it wouldn't
+         * know what to do with multi-prime key generated by builtin
+         * subroutine...
+         */
+        if (primes == 2)
+            return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);
+        else
+            return 0;
+    }
+
+    return rsa_builtin_keygen(rsa, bits, primes, e_value, cb);
+}
+
+static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,
                               BN_GENCB *cb)
 {
-    BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *r3 = NULL, *tmp;
-    int bitsp, bitsq, ok = -1, n = 0;
+    BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *prime;
+    int ok = -1, n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;
+    int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;
+    RSA_PRIME_INFO *pinfo = NULL;
+    STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;
     BN_CTX *ctx = NULL;
+    BN_ULONG bitst = 0;
     unsigned long error = 0;
 
-    /*
-     * When generating ridiculously small keys, we can get stuck
-     * continually regenerating the same prime values.
-     */
-    if (bits < 16) {
+    if (bits < RSA_MIN_MODULUS_BITS) {
         ok = 0;             /* we set our own err */
         RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_SIZE_TOO_SMALL);
         goto err;
     }
 
+    if (primes < RSA_DEFAULT_PRIME_NUM || primes > rsa_multip_cap(bits)) {
+        ok = 0;             /* we set our own err */
+        RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_PRIME_NUM_INVALID);
+        goto err;
+    }
+
     ctx = BN_CTX_new();
     if (ctx == NULL)
         goto err;
@@ -61,12 +92,15 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
     r0 = BN_CTX_get(ctx);
     r1 = BN_CTX_get(ctx);
     r2 = BN_CTX_get(ctx);
-    r3 = BN_CTX_get(ctx);
-    if (r3 == NULL)
+    if (r2 == NULL)
         goto err;
 
-    bitsp = (bits + 1) / 2;
-    bitsq = bits - bitsp;
+    /* divide bits into 'primes' pieces evenly */
+    quo = bits / primes;
+    rmd = bits % primes;
+
+    for (i = 0; i < primes; i++)
+        bitsr[i] = (i < rmd) ? quo + 1 : quo;
 
     /* We need the RSA components non-NULL */
     if (!rsa->n && ((rsa->n = BN_new()) == NULL))
@@ -86,81 +120,201 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
     if (!rsa->iqmp && ((rsa->iqmp = BN_secure_new()) == NULL))
         goto err;
 
+    /* initialize multi-prime components */
+    if (primes > RSA_DEFAULT_PRIME_NUM) {
+        rsa->version = RSA_ASN1_VERSION_MULTI;
+        prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);
+        if (prime_infos == NULL)
+            goto err;
+        if (rsa->prime_infos != NULL) {
+            /* could this happen? */
+            sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos, rsa_multip_info_free);
+        }
+        rsa->prime_infos = prime_infos;
+
+        /* prime_info from 2 to |primes| -1 */
+        for (i = 2; i < primes; i++) {
+            pinfo = rsa_multip_info_new();
+            if (pinfo == NULL)
+                goto err;
+            (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);
+        }
+    }
+
     if (BN_copy(rsa->e, e_value) == NULL)
         goto err;
 
-    BN_set_flags(r2, BN_FLG_CONSTTIME);
-    /* generate p and q */
-    for (;;) {
-        if (!BN_generate_prime_ex(rsa->p, bitsp, 0, NULL, NULL, cb))
-            goto err;
-        if (!BN_sub(r2, rsa->p, BN_value_one()))
-            goto err;
-        ERR_set_mark();
-        if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
-            /* GCD == 1 since inverse exists */
-            break;
-        }
-        error = ERR_peek_last_error();
-        if (ERR_GET_LIB(error) == ERR_LIB_BN
-            && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
-            /* GCD != 1 */
-            ERR_pop_to_mark();
+    /* generate p, q and other primes (if any) */
+    for (i = 0; i < primes; i++) {
+        adj = 0;
+        retries = 0;
+
+        if (i == 0) {
+            prime = rsa->p;
+        } else if (i == 1) {
+            prime = rsa->q;
         } else {
-            goto err;
+            pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
+            prime = pinfo->r;
         }
-        if (!BN_GENCB_call(cb, 2, n++))
-            goto err;
-    }
-    if (!BN_GENCB_call(cb, 3, 0))
-        goto err;
-    for (;;) {
-        do {
-            if (!BN_generate_prime_ex(rsa->q, bitsq, 0, NULL, NULL, cb))
+
+        for (;;) {
+ redo:
+            if (!BN_generate_prime_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))
+                goto err;
+            /*
+             * prime should not be equal to p, q, r_3...
+             * (those primes prior to this one)
+             */
+            {
+                int j;
+
+                for (j = 0; j < i; j++) {
+                    BIGNUM *prev_prime;
+
+                    if (j == 0)
+                        prev_prime = rsa->p;
+                    else if (j == 1)
+                        prev_prime = rsa->q;
+                    else
+                        prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,
+                                                             j - 2)->r;
+
+                    if (!BN_cmp(prime, prev_prime)) {
+                        goto redo;
+                    }
+                }
+            }
+            if (!BN_sub(r2, prime, BN_value_one()))
+                goto err;
+            ERR_set_mark();
+            BN_set_flags(r2, BN_FLG_CONSTTIME);
+            if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
+               /* GCD == 1 since inverse exists */
+                break;
+            }
+            error = ERR_peek_last_error();
+            if (ERR_GET_LIB(error) == ERR_LIB_BN
+                && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
+                /* GCD != 1 */
+                ERR_pop_to_mark();
+            } else {
+                goto err;
+            }
+            if (!BN_GENCB_call(cb, 2, n++))
                 goto err;
-        } while (BN_cmp(rsa->p, rsa->q) == 0);
-        if (!BN_sub(r2, rsa->q, BN_value_one()))
-            goto err;
-        ERR_set_mark();
-        if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {
-            /* GCD == 1 since inverse exists */
-            break;
         }
-        error = ERR_peek_last_error();
-        if (ERR_GET_LIB(error) == ERR_LIB_BN
-            && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {
-            /* GCD != 1 */
-            ERR_pop_to_mark();
+
+        bitse += bitsr[i];
+
+        /* calculate n immediately to see if it's sufficient */
+        if (i == 1) {
+            /* we get at least 2 primes */
+            if (!BN_mul(r1, rsa->p, rsa->q, ctx))
+                goto err;
+        } else if (i != 0) {
+            /* modulus n = p * q * r_3 * r_4 ... */
+            if (!BN_mul(r1, rsa->n, prime, ctx))
+                goto err;
         } else {
-            goto err;
+            /* i == 0, do nothing */
+            if (!BN_GENCB_call(cb, 3, i))
+                goto err;
+            continue;
         }
-        if (!BN_GENCB_call(cb, 2, n++))
+        /*
+         * if |r1|, product of factors so far, is not as long as expected
+         * (by checking the first 4 bits are less than 0x9 or greater than
+         * 0xF). If so, re-generate the last prime.
+         *
+         * NOTE: This actually can't happen in two-prime case, because of
+         * the way factors are generated.
+         *
+         * Besides, another consideration is, for multi-prime case, even the
+         * length modulus is as long as expected, the modulus could start at
+         * 0x8, which could be utilized to distinguish a multi-prime private
+         * key by using the modulus in a certificate. This is also covered
+         * by checking the length should not be less than 0x9.
+         */
+        if (!BN_rshift(r2, r1, bitse - 4))
+            goto err;
+        bitst = BN_get_word(r2);
+
+        if (bitst < 0x9 || bitst > 0xF) {
+            /*
+             * For keys with more than 4 primes, we attempt longer factor to
+             * meet length requirement.
+             *
+             * Otherwise, we just re-generate the prime with the same length.
+             *
+             * This strategy has the following goals:
+             *
+             * 1. 1024-bit factors are effcient when using 3072 and 4096-bit key
+             * 2. stay the same logic with normal 2-prime key
+             */
+            bitse -= bitsr[i];
+            if (!BN_GENCB_call(cb, 2, n++))
+                goto err;
+            if (primes > 4) {
+                if (bitst < 0x9)
+                    adj++;
+                else
+                    adj--;
+            } else if (retries == 4) {
+                /*
+                 * re-generate all primes from scratch, mainly used
+                 * in 4 prime case to avoid long loop. Max retry times
+                 * is set to 4.
+                 */
+                i = -1;
+                bitse = 0;
+                continue;
+            }
+            retries++;
+            goto redo;
+        }
+        /* save product of primes for further use, for multi-prime only */
+        if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)
+            goto err;
+        if (BN_copy(rsa->n, r1) == NULL)
+            goto err;
+        if (!BN_GENCB_call(cb, 3, i))
             goto err;
     }
-    if (!BN_GENCB_call(cb, 3, 1))
-        goto err;
+
     if (BN_cmp(rsa->p, rsa->q) < 0) {
         tmp = rsa->p;
         rsa->p = rsa->q;
         rsa->q = tmp;
     }
 
-    /* calculate n */
-    if (!BN_mul(rsa->n, rsa->p, rsa->q, ctx))
-        goto err;
-
     /* calculate d */
+
+    /* p - 1 */
     if (!BN_sub(r1, rsa->p, BN_value_one()))
-        goto err;               /* p-1 */
+        goto err;
+    /* q - 1 */
     if (!BN_sub(r2, rsa->q, BN_value_one()))
-        goto err;               /* q-1 */
+        goto err;
+    /* (p - 1)(q - 1) */
     if (!BN_mul(r0, r1, r2, ctx))
-        goto err;               /* (p-1)(q-1) */
+        goto err;
+    /* multi-prime */
+    for (i = 2; i < primes; i++) {
+        pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
+        /* save r_i - 1 to pinfo->d temporarily */
+        if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))
+            goto err;
+        if (!BN_mul(r0, r0, pinfo->d, ctx))
+            goto err;
+    }
+
     {
         BIGNUM *pr0 = BN_new();
 
         if (pr0 == NULL)
             goto err;
+
         BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);
         if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {
             BN_free(pr0);
@@ -175,15 +329,26 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
 
         if (d == NULL)
             goto err;
+
         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 
-        if (   /* calculate d mod (p-1) */
-               !BN_mod(rsa->dmp1, d, r1, ctx)
-               /* calculate d mod (q-1) */
+        /* calculate d mod (p-1) and d mod (q - 1) */
+        if (!BN_mod(rsa->dmp1, d, r1, ctx)
             || !BN_mod(rsa->dmq1, d, r2, ctx)) {
             BN_free(d);
             goto err;
         }
+
+        /* calculate CRT exponents */
+        for (i = 2; i < primes; i++) {
+            pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
+            /* pinfo->d == r_i - 1 */
+            if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {
+                BN_free(d);
+                goto err;
+            }
+        }
+
         /* We MUST free d before any further use of rsa->d */
         BN_free(d);
     }
@@ -200,6 +365,17 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
             BN_free(p);
             goto err;
         }
+
+        /* calculate CRT coefficient for other primes */
+        for (i = 2; i < primes; i++) {
+            pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);
+            BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);
+            if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {
+                BN_free(p);
+                goto err;
+            }
+        }
+
         /* We MUST free p before any further use of rsa->p */
         BN_free(p);
     }
@@ -213,6 +389,5 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
     if (ctx != NULL)
         BN_CTX_end(ctx);
     BN_CTX_free(ctx);
-
     return ok;
 }