Fix srp app missing NULL termination with password callback

The password_callback() function does not necessarily NULL terminate
the password buffer, the caller must use the returned length but the
srp app uses this function as if it was doing NULL termination.

This made the -passin and -passout options of "openssl srp"
fail inexpicably and randomly or even crash.

Fixed by enlarging the buffer by one, so that the maximum password length
remains unchanged, and adding NULL termination upon return.

[Rearrange code for coding style compliance in process.]

This backport of 0e83981d61fc435f42d4bb4d774272b69556b7bc.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3579)

1 files changed, 37 insertions, 29 deletions

diff --git a/apps/srp.c b/apps/srp.c
index ce01a24f2a..491445df60 100644
--- a/apps/srp.c
+++ b/apps/srp.c
@@ -123,13 +123,14 @@ static int get_index(CA_DB *db, char *id, char type)
     int i;
     if (id == NULL)
         return -1;
-    if (type == DB_SRP_INDEX)
+    if (type == DB_SRP_INDEX) {
         for (i = 0; i < sk_OPENSSL_PSTRING_num(db->db->data); i++) {
             pp = sk_OPENSSL_PSTRING_value(db->db->data, i);
             if (pp[DB_srptype][0] == DB_SRP_INDEX
                 && !strcmp(id, pp[DB_srpid]))
                 return i;
-    } else
+        }
+    } else {
         for (i = 0; i < sk_OPENSSL_PSTRING_num(db->db->data); i++) {
             pp = sk_OPENSSL_PSTRING_value(db->db->data, i);
 
@@ -137,6 +138,7 @@ static int get_index(CA_DB *db, char *id, char type)
                 && !strcmp(id, pp[DB_srpid]))
                 return i;
         }
+    }
 
     return -1;
 }
@@ -177,8 +179,8 @@ static int update_index(CA_DB *db, BIO *bio, char **row)
     char **irow;
     int i;
 
-    if ((irow =
-         (char **)OPENSSL_malloc(sizeof(char *) * (DB_NUMBER + 1))) == NULL) {
+    irow = (char **)OPENSSL_malloc(sizeof(char *) * (DB_NUMBER + 1));
+    if (irow == NULL) {
         BIO_printf(bio_err, "Memory allocation failure\n");
         return 0;
     }
@@ -205,30 +207,32 @@ static char *srp_verify_user(const char *user, const char *srp_verifier,
                              char *srp_usersalt, const char *g, const char *N,
                              const char *passin, BIO *bio, int verbose)
 {
-    char password[1024];
+    char password[1025];
     PW_CB_DATA cb_tmp;
     char *verifier = NULL;
     char *gNid = NULL;
+    int len;
 
     cb_tmp.prompt_info = user;
     cb_tmp.password = passin;
 
-    if (password_callback(password, 1024, 0, &cb_tmp) > 0) {
+    len = password_callback(password, sizeof(password)-1, 0, &cb_tmp);
+    if (len > 0) {
+        password[len] = 0;
         VERBOSE BIO_printf(bio,
                            "Validating\n   user=\"%s\"\n srp_verifier=\"%s\"\n srp_usersalt=\"%s\"\n g=\"%s\"\n N=\"%s\"\n",
                            user, srp_verifier, srp_usersalt, g, N);
-        BIO_printf(bio, "Pass %s\n", password);
+        VVERBOSE BIO_printf(bio, "Pass %s\n", password);
 
-        if (!
-            (gNid =
-             SRP_create_verifier(user, password, &srp_usersalt, &verifier, N,
-                                 g))) {
+        if (!(gNid = SRP_create_verifier(user, password, &srp_usersalt,
+                                         &verifier, N, g))) {
             BIO_printf(bio, "Internal error validating SRP verifier\n");
         } else {
             if (strcmp(verifier, srp_verifier))
                 gNid = NULL;
             OPENSSL_free(verifier);
         }
+        OPENSSL_cleanse(password, len);
     }
     return gNid;
 }
@@ -237,24 +241,27 @@ static char *srp_create_user(char *user, char **srp_verifier,
                              char **srp_usersalt, char *g, char *N,
                              char *passout, BIO *bio, int verbose)
 {
-    char password[1024];
+    char password[1025];
     PW_CB_DATA cb_tmp;
     char *gNid = NULL;
     char *salt = NULL;
+    int len;
     cb_tmp.prompt_info = user;
     cb_tmp.password = passout;
 
-    if (password_callback(password, 1024, 1, &cb_tmp) > 0) {
+    len = password_callback(password, sizeof(password)-1, 1, &cb_tmp);
+    if (len > 0) {
+        password[len] = 0;
         VERBOSE BIO_printf(bio,
                            "Creating\n user=\"%s\"\n g=\"%s\"\n N=\"%s\"\n",
                            user, g, N);
-        if (!
-            (gNid =
-             SRP_create_verifier(user, password, &salt, srp_verifier, N,
-                                 g))) {
+        if (!(gNid = SRP_create_verifier(user, password, &salt,
+                                         srp_verifier, N, g))) {
             BIO_printf(bio, "Internal error creating SRP verifier\n");
-        } else
+        } else {
             *srp_usersalt = salt;
+        }
+        OPENSSL_cleanse(password, len);
         VVERBOSE BIO_printf(bio, "gNid=%s salt =\"%s\"\n verifier =\"%s\"\n",
                             gNid, salt, *srp_verifier);
 
@@ -314,9 +321,9 @@ int MAIN(int argc, char **argv)
     argc--;
     argv++;
     while (argc >= 1 && badops == 0) {
-        if (strcmp(*argv, "-verbose") == 0)
+        if (strcmp(*argv, "-verbose") == 0) {
             verbose++;
-        else if (strcmp(*argv, "-config") == 0) {
+        } else if (strcmp(*argv, "-config") == 0) {
             if (--argc < 1)
                 goto bad;
             configfile = *(++argv);
@@ -328,15 +335,15 @@ int MAIN(int argc, char **argv)
             if (--argc < 1)
                 goto bad;
             dbfile = *(++argv);
-        } else if (strcmp(*argv, "-add") == 0)
+        } else if (strcmp(*argv, "-add") == 0) {
             add_user = 1;
-        else if (strcmp(*argv, "-delete") == 0)
+        } else if (strcmp(*argv, "-delete") == 0) {
             delete_user = 1;
-        else if (strcmp(*argv, "-modify") == 0)
+        } else if (strcmp(*argv, "-modify") == 0) {
             modify_user = 1;
-        else if (strcmp(*argv, "-list") == 0)
+        } else if (strcmp(*argv, "-list") == 0) {
             list_user = 1;
-        else if (strcmp(*argv, "-gn") == 0) {
+        } else if (strcmp(*argv, "-gn") == 0) {
             if (--argc < 1)
                 goto bad;
             gN = *(++argv);
@@ -366,8 +373,9 @@ int MAIN(int argc, char **argv)
             BIO_printf(bio_err, "unknown option %s\n", *argv);
             badops = 1;
             break;
-        } else
+        } else {
             break;
+        }
 
         argc--;
         argv++;
@@ -388,7 +396,7 @@ int MAIN(int argc, char **argv)
                    "Need at least one user for options -add, -delete, -modify. \n");
         badops = 1;
     }
-    if ((passin || passout) && argc != 1) {
+    if ((passargin || passargout) && argc != 1) {
         BIO_printf(bio_err,
                    "-passin, -passout arguments only valid with one user.\n");
         badops = 1;
@@ -706,9 +714,9 @@ int MAIN(int argc, char **argv)
                 doupdatedb = 1;
             }
         }
-        if (--argc > 0)
+        if (--argc > 0) {
             user = *(argv++);
-        else {
+        } else {
             user = NULL;
             list_user = 0;
         }