basic: util - fix errorhandling in unhexmem()

We were ignoring failures from unhexchar, which meant that invalid
hex characters were being turned into garbage rather than the string
rejected.

Fix this by making unhexmem return an error code, also change the API
slightly, to return the size of the returned memory, reflecting the
fact that the memory is a binary blob,and not a string.

For convenience, still append a trailing NULL byte to the returned
memory (not included in the returned size), allowing callers to
treat it as a string without doing a second copy.

2 files changed, 19 insertions, 7 deletions

diff --git a/src/basic/util.c b/src/basic/util.c
index 13a67e9ab8..61dd6c4227 100644
--- a/src/basic/util.c
+++ b/src/basic/util.c
@@ -916,30 +916,42 @@ char *hexmem(const void *p, size_t l) {
         return r;
 }
 
-void *unhexmem(const char *p, size_t l) {
-        uint8_t *r, *z;
+int unhexmem(const char *p, size_t l, void **mem, size_t *len) {
+        _cleanup_free_ uint8_t *r = NULL;
+        uint8_t *z;
         const char *x;
 
+        assert(mem);
+        assert(len);
         assert(p);
 
         z = r = malloc((l + 1) / 2 + 1);
         if (!r)
-                return NULL;
+                return -ENOMEM;
 
         for (x = p; x < p + l; x += 2) {
                 int a, b;
 
                 a = unhexchar(x[0]);
-                if (x+1 < p + l)
+                if (a < 0)
+                        return a;
+                else if (x+1 < p + l) {
                         b = unhexchar(x[1]);
-                else
+                        if (b < 0)
+                                return b;
+                } else
                         b = 0;
 
                 *(z++) = (uint8_t) a << 4 | (uint8_t) b;
         }
 
         *z = 0;
-        return r;
+
+        *mem = r;
+        r = NULL;
+        *len = (l + 1) / 2;
+
+        return 0;
 }
 
 char octchar(int x) {
diff --git a/src/basic/util.h b/src/basic/util.h
index a1d1dd15c3..ea77907f7f 100644
--- a/src/basic/util.h
+++ b/src/basic/util.h
@@ -614,7 +614,7 @@ static inline void *mempset(void *s, int c, size_t n) {
 }
 
 char *hexmem(const void *p, size_t l);
-void *unhexmem(const char *p, size_t l);
+int unhexmem(const char *p, size_t l, void **mem, size_t *len);
 
 char *strextend(char **x, ...) _sentinel_;
 char *strrep(const char *s, unsigned n);