Merge pull request #3745 from keszybz/fix-make-nulstr-confusion

Fix make nulstr confusion

3 files changed, 32 insertions, 9 deletions

diff --git a/src/basic/strv.c b/src/basic/strv.c
index db315ac10a..34e464d253 100644
--- a/src/basic/strv.c
+++ b/src/basic/strv.c
@@ -638,6 +638,17 @@ char **strv_remove(char **l, const char *s) {
 }
 
 char **strv_parse_nulstr(const char *s, size_t l) {
+        /* l is the length of the input data, which will be split at NULs into
+         * elements of the resulting strv. Hence, the number of items in the resulting strv
+         * will be equal to one plus the number of NUL bytes in the l bytes starting at s,
+         * unless s[l-1] is NUL, in which case the final empty string is not stored in
+         * the resulting strv, and length is equal to the number of NUL bytes.
+         *
+         * Note that contrary to a normal nulstr which cannot contain empty strings, because
+         * the input data is terminated by any two consequent NUL bytes, this parser accepts
+         * empty strings in s.
+         */
+
         const char *p;
         unsigned c = 0, i = 0;
         char **v;
@@ -700,6 +711,13 @@ char **strv_split_nulstr(const char *s) {
 }
 
 int strv_make_nulstr(char **l, char **p, size_t *q) {
+        /* A valid nulstr with two NULs at the end will be created, but
+         * q will be the length without the two trailing NULs. Thus the output
+         * string is a valid nulstr and can be iterated over using NULSTR_FOREACH,
+         * and can also be parsed by strv_parse_nulstr as long as the length
+         * is provided separately.
+         */
+
         size_t n_allocated = 0, n = 0;
         _cleanup_free_ char *m = NULL;
         char **i;
@@ -712,7 +730,7 @@ int strv_make_nulstr(char **l, char **p, size_t *q) {
 
                 z = strlen(*i);
 
-                if (!GREEDY_REALLOC(m, n_allocated, n + z + 1))
+                if (!GREEDY_REALLOC(m, n_allocated, n + z + 2))
                         return -ENOMEM;
 
                 memcpy(m + n, *i, z + 1);
@@ -723,11 +741,14 @@ int strv_make_nulstr(char **l, char **p, size_t *q) {
                 m = new0(char, 1);
                 if (!m)
                         return -ENOMEM;
-                n = 0;
-        }
+                n = 1;
+        } else
+                /* make sure there is a second extra NUL at the end of resulting nulstr */
+                m[n] = '\0';
 
+        assert(n > 0);
         *p = m;
-        *q = n;
+        *q = n - 1;
 
         m = NULL;
 
diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index a86b0db554..65151b19a6 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -139,11 +139,7 @@ static int add_to_keyring(const char *keyname, AskPasswordFlags flags, char **pa
         if (r < 0)
                 return r;
 
-        /* Truncate trailing NUL */
-        assert(n > 0);
-        assert(p[n-1] == 0);
-
-        serial = add_key("user", keyname, p, n-1, KEY_SPEC_USER_KEYRING);
+        serial = add_key("user", keyname, p, n, KEY_SPEC_USER_KEYRING);
         memory_erase(p, n);
         if (serial == -1)
                 return -errno;
diff --git a/src/test/test-strv.c b/src/test/test-strv.c
index f7a1217df7..841a36782f 100644
--- a/src/test/test-strv.c
+++ b/src/test/test-strv.c
@@ -647,7 +647,9 @@ static void test_strv_extend_n(void) {
 static void test_strv_make_nulstr_one(char **l) {
         _cleanup_free_ char *b = NULL, *c = NULL;
         _cleanup_strv_free_ char **q = NULL;
+        const char *s = NULL;
         size_t n, m;
+        unsigned i = 0;
 
         assert_se(strv_make_nulstr(l, &b, &n) >= 0);
         assert_se(q = strv_parse_nulstr(b, n));
@@ -656,6 +658,10 @@ static void test_strv_make_nulstr_one(char **l) {
         assert_se(strv_make_nulstr(q, &c, &m) >= 0);
         assert_se(m == n);
         assert_se(memcmp(b, c, m) == 0);
+
+        NULSTR_FOREACH(s, b)
+                assert_se(streq(s, l[i++]));
+        assert_se(i == strv_length(l));
 }
 
 static void test_strv_make_nulstr(void) {