OSSL_PARAM: Correct the assumptions on the UTF8 string length

When the string "ABCDEFGH" is passed, what's considered its data, this?

    { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H' }

or this?

    { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', '\0' }

If it's passed as a pass phrase, should the terminating NUL byte be
considered part of the pass phrase, or not?

Our treatment of OSSL_PARAMs with the data type OSSL_PARAM_UTF8_STRING
set the length of the string to include the terminating NUL byte,
which is quite confusing.  What should the recipient of such a string
believe?

Instead of perpetuating this confusion, we change the assumption to
set the OSSL_PARAM to the length of the string, not including the
terminating NUL byte, thereby giving it the same value as a strlen()
call would give.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14168)

6 files changed, 98 insertions, 59 deletions

diff --git a/crypto/params.c b/crypto/params.c
index e28affe708..a3263e93c3 100644
--- a/crypto/params.c
+++ b/crypto/params.c
@@ -1070,15 +1070,21 @@ OSSL_PARAM OSSL_PARAM_construct_double(const char *key, double *buf)
     return ossl_param_construct(key, OSSL_PARAM_REAL, buf, sizeof(double));
 }
 
-static int get_string_internal(const OSSL_PARAM *p, void **val, size_t max_len,
-                               size_t *used_len, unsigned int type)
+static int get_string_internal(const OSSL_PARAM *p, void **val,
+                               size_t *max_len, size_t *used_len,
+                               unsigned int type)
 {
-    size_t sz;
+    size_t sz, alloc_sz;
 
     if ((val == NULL && used_len == NULL) || p == NULL || p->data_type != type)
         return 0;
 
     sz = p->data_size;
+    /*
+     * If the input size is 0, or the input string needs NUL byte
+     * termination, allocate an extra byte.
+     */
+    alloc_sz = sz + (type == OSSL_PARAM_UTF8_STRING || sz == 0);
 
     if (used_len != NULL)
         *used_len = sz;
@@ -1090,16 +1096,15 @@ static int get_string_internal(const OSSL_PARAM *p, void **val, size_t max_len,
         return 1;
 
     if (*val == NULL) {
-        char *const q = OPENSSL_malloc(sz > 0 ? sz : 1);
+        char *const q = OPENSSL_malloc(alloc_sz);
 
         if (q == NULL)
             return 0;
         *val = q;
-        if (sz != 0)
-            memcpy(q, p->data, sz);
-        return 1;
+        *max_len = alloc_sz;
     }
-    if (max_len < sz)
+
+    if (*max_len < sz)
         return 0;
     memcpy(*val, p->data, sz);
     return 1;
@@ -1107,14 +1112,35 @@ static int get_string_internal(const OSSL_PARAM *p, void **val, size_t max_len,
 
 int OSSL_PARAM_get_utf8_string(const OSSL_PARAM *p, char **val, size_t max_len)
 {
-    return get_string_internal(p, (void **)val, max_len, NULL,
-                               OSSL_PARAM_UTF8_STRING);
+    int ret = get_string_internal(p, (void **)val, &max_len, NULL,
+                                  OSSL_PARAM_UTF8_STRING);
+
+    /*
+     * We try to ensure that the copied string is terminated with a
+     * NUL byte.  That should be easy, just place a NUL byte at
+     * |((char*)*val)[p->data_size]|.
+     * Unfortunately, we have seen cases where |p->data_size| doesn't
+     * correctly reflect the length of the string, and just happens
+     * to be out of bounds according to |max_len|, so in that case, we
+     * make the extra step of trying to find the true length of the
+     * string that |p->data| points at, and use that as an index to
+     * place the NUL byte in |*val|.
+     */
+    size_t data_length = p->data_size;
+
+    if (data_length >= max_len)
+        data_length = OPENSSL_strnlen(p->data, data_length);
+    if (data_length >= max_len)
+        return 0;            /* No space for a terminating NUL byte */
+    ((char *)*val)[data_length] = '\0';
+
+    return ret;
 }
 
 int OSSL_PARAM_get_octet_string(const OSSL_PARAM *p, void **val, size_t max_len,
                                 size_t *used_len)
 {
-    return get_string_internal(p, val, max_len, used_len,
+    return get_string_internal(p, val, &max_len, used_len,
                                OSSL_PARAM_OCTET_STRING);
 }
 
@@ -1128,6 +1154,9 @@ static int set_string_internal(OSSL_PARAM *p, const void *val, size_t len,
         return 0;
 
     memcpy(p->data, val, len);
+    /* If possible within the size of p->data, add a NUL terminator byte */
+    if (type == OSSL_PARAM_UTF8_STRING && p->data_size > len)
+        ((char *)p->data)[len] = '\0';
     return 1;
 }
 
@@ -1139,7 +1168,7 @@ int OSSL_PARAM_set_utf8_string(OSSL_PARAM *p, const char *val)
     p->return_size = 0;
     if (val == NULL)
         return 0;
-    return set_string_internal(p, val, strlen(val) + 1, OSSL_PARAM_UTF8_STRING);
+    return set_string_internal(p, val, strlen(val), OSSL_PARAM_UTF8_STRING);
 }
 
 int OSSL_PARAM_set_octet_string(OSSL_PARAM *p, const void *val,
@@ -1158,7 +1187,7 @@ OSSL_PARAM OSSL_PARAM_construct_utf8_string(const char *key, char *buf,
                                             size_t bsize)
 {
     if (buf != NULL && bsize == 0)
-        bsize = strlen(buf) + 1;
+        bsize = strlen(buf);
     return ossl_param_construct(key, OSSL_PARAM_UTF8_STRING, buf, bsize);
 }
 
@@ -1207,7 +1236,7 @@ int OSSL_PARAM_set_utf8_ptr(OSSL_PARAM *p, const char *val)
         return 0;
     p->return_size = 0;
     return set_ptr_internal(p, val, OSSL_PARAM_UTF8_PTR,
-                            val == NULL ? 0 : strlen(val) + 1);
+                            val == NULL ? 0 : strlen(val));
 }
 
 int OSSL_PARAM_set_octet_ptr(OSSL_PARAM *p, const void *val,
diff --git a/doc/man3/OSSL_PARAM.pod b/doc/man3/OSSL_PARAM.pod
index fdf376a206..99f4e2ce62 100644
--- a/doc/man3/OSSL_PARAM.pod
+++ b/doc/man3/OSSL_PARAM.pod
@@ -97,6 +97,13 @@ setting parameters) or shall (when requesting parameters) be stored,
 and I<data_size> is its size in bytes.
 The organization of the data depends on the parameter type and flag.
 
+The I<data_size> needs special attention with the parameter type
+B<OSSL_PARAM_UTF8_STRING> in relation to C strings.  When setting
+parameters, the size should be set to the length of the string, not
+counting the terminating NUL byte.  When requesting parameters, the
+size should be set to the size of the buffer to be populated, which
+should accomodate enough space for a terminating NUL byte.
+
 When I<requesting parameters>, it's acceptable for I<data> to be NULL.
 This can be used by the I<requestor> to figure out dynamically exactly
 how much buffer space is needed to store the parameter data.
diff --git a/doc/man3/OSSL_PARAM_int.pod b/doc/man3/OSSL_PARAM_int.pod
index d637d94f8a..25b87014b7 100644
--- a/doc/man3/OSSL_PARAM_int.pod
+++ b/doc/man3/OSSL_PARAM_int.pod
@@ -184,8 +184,7 @@ size I<rsize> is created.
 OSSL_PARAM_construct_utf8_string() is a function that constructs a UTF8
 string OSSL_PARAM structure.
 A parameter with name I<key>, storage I<buf> and size I<bsize> is created.
-If I<bsize> is zero, the string length is determined using strlen(3) + 1 for the
-null termination byte.
+If I<bsize> is zero, the string length is determined using strlen(3).
 Generally pass zero for I<bsize> instead of calling strlen(3) yourself.
 
 OSSL_PARAM_construct_octet_string() is a function that constructs an OCTET
@@ -232,15 +231,18 @@ will be assigned the size the parameter's I<data> buffer should have.
 
 OSSL_PARAM_get_utf8_string() retrieves a UTF8 string from the parameter
 pointed to by I<p>.
-The string is either stored into I<*val> with a length limit of I<max_len> or,
-in the case when I<*val> is NULL, memory is allocated for the string and
-I<max_len> is ignored.
+The string is stored into I<*val> with a size limit of I<max_len>,
+which must be large enough to accomodate a terminating NUL byte,
+otherwise this function will fail.
+If I<*val> is NULL, memory is allocated for the string and I<max_len>
+is ignored.
 If memory is allocated by this function, it must be freed by the caller.
 
 OSSL_PARAM_set_utf8_string() sets a UTF8 string from the parameter pointed to
 by I<p> to the value referenced by I<val>.
 If the parameter's I<data> field is NULL, then only its I<return_size> field
-will be assigned the size the parameter's I<data> buffer should have.
+will be assigned the minimum size the parameter's I<data> buffer should have
+to accomodate the string, including a terminating NUL byte.
 
 OSSL_PARAM_get_octet_string() retrieves an OCTET string from the parameter
 pointed to by I<p>.
@@ -334,11 +336,11 @@ This example is for setting parameters on some object:
     #include <openssl/core.h>
 
     const char *foo = "some string";
-    size_t foo_l = strlen(foo) + 1;
+    size_t foo_l = strlen(foo);
     const char bar[] = "some other string";
     const OSSL_PARAM set[] = {
         OSSL_PARAM_utf8_ptr("foo", &foo, foo_l),
-        OSSL_PARAM_utf8_string("bar", bar, sizeof(bar)),
+        OSSL_PARAM_utf8_string("bar", bar, sizeof(bar) - 1),
         OSSL_PARAM_END
     };
 
@@ -366,7 +368,7 @@ could fill in the parameters like this:
     if ((p = OSSL_PARAM_locate(params, "foo")) != NULL)
         OSSL_PARAM_set_utf8_ptr(p, "foo value");
     if ((p = OSSL_PARAM_locate(params, "bar")) != NULL)
-        OSSL_PARAM_set_utf8_ptr(p, "bar value");
+        OSSL_PARAM_set_utf8_string(p, "bar value");
     if ((p = OSSL_PARAM_locate(params, "cookie")) != NULL)
         OSSL_PARAM_set_utf8_ptr(p, "cookie value");
 
diff --git a/doc/man7/EVP_KDF-SSHKDF.pod b/doc/man7/EVP_KDF-SSHKDF.pod
index f0e113c6c8..a2ff902cce 100644
--- a/doc/man7/EVP_KDF-SSHKDF.pod
+++ b/doc/man7/EVP_KDF-SSHKDF.pod
@@ -124,7 +124,7 @@ This example derives an 8 byte IV using SHA-256 with a 1K "key" and appropriate
  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
                                           session_id, (size_t)32);
  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE,
-                                         type, sizeof(type));
+                                         type, sizeof(type) - 1);
  *p = OSSL_PARAM_construct_end();
  if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
      /* Error */
diff --git a/test/params_api_test.c b/test/params_api_test.c
index 0a68b9c462..2d69b5c327 100644
--- a/test/params_api_test.c
+++ b/test/params_api_test.c
@@ -538,7 +538,7 @@ static int test_param_construct(void)
     bufp = NULL;
     if (!TEST_ptr(cp = OSSL_PARAM_locate(params, "utf8str"))
         || !TEST_true(OSSL_PARAM_set_utf8_string(cp, "abcdef"))
-        || !TEST_size_t_eq(cp->return_size, sizeof("abcdef"))
+        || !TEST_size_t_eq(cp->return_size, sizeof("abcdef") - 1)
         || !TEST_true(OSSL_PARAM_get_utf8_string(cp, &bufp, 0))
         || !TEST_str_eq(bufp, "abcdef"))
         goto err;
@@ -548,10 +548,11 @@ static int test_param_construct(void)
         || !TEST_str_eq(buf2, "abcdef"))
         goto err;
     /* UTF8 pointer */
+    /* Note that the size of a UTF8 string does *NOT* include the NUL byte */
     bufp = buf;
     if (!TEST_ptr(cp = OSSL_PARAM_locate(params, "utf8ptr"))
         || !TEST_true(OSSL_PARAM_set_utf8_ptr(cp, "tuvwxyz"))
-        || !TEST_size_t_eq(cp->return_size, sizeof("tuvwxyz"))
+        || !TEST_size_t_eq(cp->return_size, sizeof("tuvwxyz") - 1)
         || !TEST_str_eq(bufp, "tuvwxyz")
         || !TEST_true(OSSL_PARAM_get_utf8_ptr(cp, (const char **)&bufp2))
         || !TEST_ptr_eq(bufp2, bufp))
diff --git a/test/params_test.c b/test/params_test.c
index 9729ab892b..dd2d13b862 100644
--- a/test/params_test.c
+++ b/test/params_test.c
@@ -141,9 +141,20 @@ static int raw_set_params(void *vobj, const OSSL_PARAM *params)
             if (!TEST_ptr(obj->p4 = OPENSSL_strndup(params->data,
                                                     params->data_size)))
                 return 0;
+            obj->p4_l = strlen(obj->p4);
         } else if (strcmp(params->key, "p5") == 0) {
-            strncpy(obj->p5, params->data, params->data_size);
-            obj->p5_l = strlen(obj->p5) + 1;
+            /*
+             * Protect obj->p5 against too much data.  This should not
+             * happen, we don't use that long strings.
+             */
+            size_t data_length =
+                OPENSSL_strnlen(params->data, params->data_size);
+
+            if (!TEST_size_t_lt(data_length, sizeof(obj->p5)))
+                return 0;
+            strncpy(obj->p5, params->data, data_length);
+            obj->p5[data_length] = '\0';
+            obj->p5_l = strlen(obj->p5);
         } else if (strcmp(params->key, "p6") == 0) {
             obj->p6 = *(const char **)params->data;
             obj->p6_l = params->data_size;
@@ -164,36 +175,22 @@ static int raw_get_params(void *vobj, OSSL_PARAM *params)
             params->return_size = sizeof(obj->p2);
             *(double *)params->data = obj->p2;
         } else if (strcmp(params->key, "p3") == 0) {
-            size_t bytes = BN_num_bytes(obj->p3);
-
-            params->return_size = bytes;
-            if (!TEST_size_t_ge(params->data_size, bytes))
+            params->return_size = BN_num_bytes(obj->p3);
+            if (!TEST_size_t_ge(params->data_size, params->return_size))
                 return 0;
-            BN_bn2nativepad(obj->p3, params->data, bytes);
+            BN_bn2nativepad(obj->p3, params->data, params->return_size);
         } else if (strcmp(params->key, "p4") == 0) {
-            size_t bytes = strlen(obj->p4) + 1;
-
-            params->return_size = bytes;
-            if (!TEST_size_t_ge(params->data_size, bytes))
+            params->return_size = strlen(obj->p4);
+            if (!TEST_size_t_gt(params->data_size, params->return_size))
                 return 0;
             strcpy(params->data, obj->p4);
         } else if (strcmp(params->key, "p5") == 0) {
-            size_t bytes = strlen(obj->p5) + 1;
-
-            params->return_size = bytes;
-            if (!TEST_size_t_ge(params->data_size, bytes))
+            params->return_size = strlen(obj->p5);
+            if (!TEST_size_t_gt(params->data_size, params->return_size))
                 return 0;
             strcpy(params->data, obj->p5);
         } else if (strcmp(params->key, "p6") == 0) {
-            /*
-             * We COULD also use OPENSSL_FULL_VERSION_STR directly and
-             * use sizeof(OPENSSL_FULL_VERSION_STR) instead of calling
-             * strlen().
-             * The caller wouldn't know the difference.
-             */
-            size_t bytes = strlen(obj->p6) + 1;
-
-            params->return_size = bytes;
+            params->return_size = strlen(obj->p6);
             *(const char **)params->data = obj->p6;
         }
 
@@ -229,12 +226,12 @@ static int api_set_params(void *vobj, const OSSL_PARAM *params)
         char *p5_ptr = obj->p5;
         if (!TEST_true(OSSL_PARAM_get_utf8_string(p, &p5_ptr, sizeof(obj->p5))))
             return 0;
-        obj->p5_l = strlen(obj->p5) + 1;
+        obj->p5_l = strlen(obj->p5);
     }
     if ((p = OSSL_PARAM_locate_const(params, "p6")) != NULL) {
         if (!TEST_true(OSSL_PARAM_get_utf8_ptr(p, &obj->p6)))
             return 0;
-        obj->p6_l = strlen(obj->p6) + 1;
+        obj->p6_l = strlen(obj->p6);
     }
 
     return 1;
@@ -353,8 +350,8 @@ static OSSL_PARAM static_raw_params[] = {
     { "p3", OSSL_PARAM_UNSIGNED_INTEGER, &bignumbin, sizeof(bignumbin), 0 },
     { "p4", OSSL_PARAM_UTF8_STRING, &app_p4, sizeof(app_p4), 0 },
     { "p5", OSSL_PARAM_UTF8_STRING, &app_p5, sizeof(app_p5), 0 },
-    /* sizeof(app_p6_init), because we know that's what we're using */
-    { "p6", OSSL_PARAM_UTF8_PTR, &app_p6, sizeof(app_p6_init), 0 },
+    /* sizeof(app_p6_init) - 1, because we know that's what we're using */
+    { "p6", OSSL_PARAM_UTF8_PTR, &app_p6, sizeof(app_p6_init) - 1, 0 },
     { "foo", OSSL_PARAM_OCTET_STRING, &foo, sizeof(foo), 0 },
     { NULL, 0, NULL, 0, 0 }
 };
@@ -366,7 +363,8 @@ static OSSL_PARAM static_api_params[] = {
     OSSL_PARAM_DEFN("p4", OSSL_PARAM_UTF8_STRING, &app_p4, sizeof(app_p4)),
     OSSL_PARAM_DEFN("p5", OSSL_PARAM_UTF8_STRING, &app_p5, sizeof(app_p5)),
     /* sizeof(app_p6_init), because we know that's what we're using */
-    OSSL_PARAM_DEFN("p6", OSSL_PARAM_UTF8_PTR, &app_p6, sizeof(app_p6_init)),
+    OSSL_PARAM_DEFN("p6", OSSL_PARAM_UTF8_PTR, &app_p6,
+                    sizeof(app_p6_init) - 1),
     OSSL_PARAM_DEFN("foo", OSSL_PARAM_OCTET_STRING, &foo, sizeof(foo)),
     OSSL_PARAM_END
 };
@@ -461,10 +459,12 @@ static int test_case_variant(OSSL_PARAM *params, const struct provider_dispatch_
         || !TEST_BN_eq(app_p3, verify_p3)       /* "provider" value */
         || !TEST_str_eq(app_p4, p4_init)        /* "provider" value */
         || !TEST_ptr(p = OSSL_PARAM_locate(params, "p5"))
-        || !TEST_size_t_eq(p->return_size, sizeof(p5_init)) /* "provider" value */
+        || !TEST_size_t_eq(p->return_size,
+                           sizeof(p5_init) - 1) /* "provider" value */
         || !TEST_str_eq(app_p5, p5_init)        /* "provider" value */
         || !TEST_ptr(p = OSSL_PARAM_locate(params, "p6"))
-        || !TEST_size_t_eq(p->return_size, sizeof(p6_init)) /* "provider" value */
+        || !TEST_size_t_eq(p->return_size,
+                           sizeof(p6_init) - 1) /* "provider" value */
         || !TEST_str_eq(app_p6, p6_init)        /* "provider" value */
         || !TEST_char_eq(foo[0], app_foo_init)  /* Should remain untouched */
         || !TEST_ptr(p = OSSL_PARAM_locate(params, "foo")))
@@ -511,11 +511,11 @@ static int test_case_variant(OSSL_PARAM *params, const struct provider_dispatch_
         || !TEST_str_eq(app_p4, app_p4_init)    /* app value */
         || !TEST_ptr(p = OSSL_PARAM_locate(params, "p5"))
         || !TEST_size_t_eq(p->return_size,
-                           sizeof(app_p5_init)) /* app value */
+                           sizeof(app_p5_init) - 1) /* app value */
         || !TEST_str_eq(app_p5, app_p5_init)    /* app value */
         || !TEST_ptr(p = OSSL_PARAM_locate(params, "p6"))
         || !TEST_size_t_eq(p->return_size,
-                           sizeof(app_p6_init)) /* app value */
+                           sizeof(app_p6_init) - 1) /* app value */
         || !TEST_str_eq(app_p6, app_p6_init)    /* app value */
         || !TEST_char_eq(foo[0], app_foo_init)  /* Should remain untouched */
         || !TEST_ptr(p = OSSL_PARAM_locate(params, "foo")))