constify SRP

Add const qualifiers to lots of SRP stuff. This started out as an effort
to silence some "type-punning" warnings on OpenBSD...but the fix was to
have proper const correctness in SRP.

RT4378

Reviewed-by: Richard Levitte <levitte@openssl.org>

3 files changed, 44 insertions, 41 deletions

diff --git a/crypto/srp/srp_lib.c b/crypto/srp/srp_lib.c
index 766a0a23be..06671749a6 100644
--- a/crypto/srp/srp_lib.c
+++ b/crypto/srp/srp_lib.c
@@ -14,7 +14,7 @@
 # include <openssl/evp.h>
 # include "internal/bn_srp.h"
 
-static BIGNUM *srp_Calc_k(BIGNUM *N, BIGNUM *g)
+static BIGNUM *srp_Calc_k(const BIGNUM *N, const BIGNUM *g)
 {
     /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
 
@@ -52,7 +52,7 @@ static BIGNUM *srp_Calc_k(BIGNUM *N, BIGNUM *g)
     return res;
 }
 
-BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N)
+BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N)
 {
     /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
 
@@ -95,8 +95,8 @@ BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N)
     return u;
 }
 
-BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b,
-                            BIGNUM *N)
+BIGNUM *SRP_Calc_server_key(const BIGNUM *A, const BIGNUM *v, const BIGNUM *u,
+                            const BIGNUM *b, const BIGNUM *N)
 {
     BIGNUM *tmp = NULL, *S = NULL;
     BN_CTX *bn_ctx;
@@ -125,7 +125,8 @@ BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b,
     return S;
 }
 
-BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v)
+BIGNUM *SRP_Calc_B(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,
+                   const BIGNUM *v)
 {
     BIGNUM *kv = NULL, *gb = NULL;
     BIGNUM *B = NULL, *k = NULL;
@@ -156,7 +157,7 @@ BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v)
     return B;
 }
 
-BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass)
+BIGNUM *SRP_Calc_x(const BIGNUM *s, const char *user, const char *pass)
 {
     unsigned char dig[SHA_DIGEST_LENGTH];
     EVP_MD_CTX *ctxt;
@@ -191,7 +192,7 @@ BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass)
     return res;
 }
 
-BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g)
+BIGNUM *SRP_Calc_A(const BIGNUM *a, const BIGNUM *N, const BIGNUM *g)
 {
     BN_CTX *bn_ctx;
     BIGNUM *A = NULL;
@@ -207,8 +208,8 @@ BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g)
     return A;
 }
 
-BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x,
-                            BIGNUM *a, BIGNUM *u)
+BIGNUM *SRP_Calc_client_key(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,
+                            const BIGNUM *x, const BIGNUM *a, const BIGNUM *u)
 {
     BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;
     BN_CTX *bn_ctx;
@@ -249,7 +250,7 @@ BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x,
     return K;
 }
 
-int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N)
+int SRP_Verify_B_mod_N(const BIGNUM *B, const BIGNUM *N)
 {
     BIGNUM *r;
     BN_CTX *bn_ctx;
@@ -270,20 +271,20 @@ int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N)
     return ret;
 }
 
-int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N)
+int SRP_Verify_A_mod_N(const BIGNUM *A, const BIGNUM *N)
 {
     /* Checks if A % N == 0 */
     return SRP_Verify_B_mod_N(A, N);
 }
 
 static SRP_gN knowngN[] = {
-    {"8192", (BIGNUM *)&bn_generator_19, (BIGNUM *)&bn_group_8192},
-    {"6144", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_6144},
-    {"4096", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_4096},
-    {"3072", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_3072},
-    {"2048", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_2048},
-    {"1536", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_1536},
-    {"1024", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_1024},
+    {"8192", &bn_generator_19, &bn_group_8192},
+    {"6144", &bn_generator_5, &bn_group_6144},
+    {"4096", &bn_generator_5, &bn_group_4096},
+    {"3072", &bn_generator_5, &bn_group_3072},
+    {"2048", &bn_generator_2, &bn_group_2048},
+    {"1536", &bn_generator_2, &bn_group_1536},
+    {"1024", &bn_generator_2, &bn_group_1024},
 };
 
 # define KNOWN_GN_NUMBER sizeof(knowngN) / sizeof(SRP_gN)
@@ -292,7 +293,7 @@ static SRP_gN knowngN[] = {
  * Check if G and N are known parameters. The values have been generated
  * from the ietf-tls-srp draft version 8
  */
-char *SRP_check_known_gN_param(BIGNUM *g, BIGNUM *N)
+char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N)
 {
     size_t i;
     if ((g == NULL) || (N == NULL))
diff --git a/crypto/srp/srp_vfy.c b/crypto/srp/srp_vfy.c
index 11b9a4b58c..f99fa1b278 100644
--- a/crypto/srp/srp_vfy.c
+++ b/crypto/srp/srp_vfy.c
@@ -525,7 +525,8 @@ char *SRP_create_verifier(const char *user, const char *pass, char **salt,
 {
     int len;
     char *result = NULL, *vf = NULL;
-    BIGNUM *N_bn = NULL, *g_bn = NULL, *s = NULL, *v = NULL;
+    const BIGNUM *N_bn = NULL, *g_bn = NULL;
+    BIGNUM *N_bn_alloc = NULL, *g_bn_alloc = NULL, *s = NULL, *v = NULL;
     unsigned char tmp[MAX_LEN];
     unsigned char tmp2[MAX_LEN];
     char *defgNid = NULL;
@@ -538,10 +539,12 @@ char *SRP_create_verifier(const char *user, const char *pass, char **salt,
     if (N) {
         if ((len = t_fromb64(tmp, N)) == 0)
             goto err;
-        N_bn = BN_bin2bn(tmp, len, NULL);
+        N_bn_alloc = BN_bin2bn(tmp, len, NULL);
+        N_bn = N_bn_alloc;
         if ((len = t_fromb64(tmp, g)) == 0)
             goto err;
-        g_bn = BN_bin2bn(tmp, len, NULL);
+        g_bn_alloc = BN_bin2bn(tmp, len, NULL);
+        g_bn = g_bn_alloc;
         defgNid = "*";
     } else {
         SRP_gN *gN = SRP_get_gN_by_id(g, NULL);
@@ -587,10 +590,8 @@ char *SRP_create_verifier(const char *user, const char *pass, char **salt,
     result = defgNid;
 
  err:
-    if (N) {
-        BN_free(N_bn);
-        BN_free(g_bn);
-    }
+    BN_free(N_bn_alloc);
+    BN_free(g_bn_alloc);
     OPENSSL_clear_free(vf, vfsize);
     BN_clear_free(s);
     BN_clear_free(v);
diff --git a/include/openssl/srp.h b/include/openssl/srp.h
index 1007b8321b..80bcb0dd38 100644
--- a/include/openssl/srp.h
+++ b/include/openssl/srp.h
@@ -52,8 +52,8 @@ typedef struct SRP_VBASE_st {
     STACK_OF(SRP_gN_cache) *gN_cache;
 /* to simulate a user */
     char *seed_key;
-    BIGNUM *default_g;
-    BIGNUM *default_N;
+    const BIGNUM *default_g;
+    const BIGNUM *default_N;
 } SRP_VBASE;
 
 /*
@@ -61,8 +61,8 @@ typedef struct SRP_VBASE_st {
  */
 typedef struct SRP_gN_st {
     char *id;
-    BIGNUM *g;
-    BIGNUM *N;
+    const BIGNUM *g;
+    const BIGNUM *N;
 } SRP_gN;
 
 DEFINE_STACK_OF(SRP_gN)
@@ -103,22 +103,23 @@ int SRP_create_verifier_BN(const char *user, const char *pass, BIGNUM **salt,
 # define DB_SRP_MODIF    'v'
 
 /* see srp.c */
-char *SRP_check_known_gN_param(BIGNUM *g, BIGNUM *N);
+char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N);
 SRP_gN *SRP_get_default_gN(const char *id);
 
 /* server side .... */
-BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b,
-                            BIGNUM *N);
-BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v);
-int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N);
-BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N);
+BIGNUM *SRP_Calc_server_key(const BIGNUM *A, const BIGNUM *v, const BIGNUM *u,
+                            const BIGNUM *b, const BIGNUM *N);
+BIGNUM *SRP_Calc_B(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,
+                   const BIGNUM *v);
+int SRP_Verify_A_mod_N(const BIGNUM *A, const BIGNUM *N);
+BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N);
 
 /* client side .... */
-BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass);
-BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g);
-BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x,
-                            BIGNUM *a, BIGNUM *u);
-int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N);
+BIGNUM *SRP_Calc_x(const BIGNUM *s, const char *user, const char *pass);
+BIGNUM *SRP_Calc_A(const BIGNUM *a, const BIGNUM *N, const BIGNUM *g);
+BIGNUM *SRP_Calc_client_key(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,
+                            const BIGNUM *x, const BIGNUM *a, const BIGNUM *u);
+int SRP_Verify_B_mod_N(const BIGNUM *B, const BIGNUM *N);
 
 # define SRP_MINIMAL_N 1024