try not to call memcpy with length 0 in hash calculations

memcpy is marked as nonnull for its input, but ignores the input anyhow
if the declared length is zero. Our SHA2 implementations do this as
well, it was "just" MD5 and SHA1 missing, so we add the length check
here as well as along the callstack as it is really pointless to do all
these method calls for "nothing".

Reported-By: gcc -fsanitize=undefined
(cherry picked from commit 644478e8db56f305601c3628a74e53de048b28c8)

1 files changed, 6 insertions, 6 deletions

diff --git a/apt-pkg/contrib/hashsum_template.h b/apt-pkg/contrib/hashsum_template.h
index 4000f230d..e5032d02f 100644
--- a/apt-pkg/contrib/hashsum_template.h
+++ b/apt-pkg/contrib/hashsum_template.h
@@ -122,18 +122,18 @@ class HashSumValue
 class SummationImplementation
 {
    public:
-   virtual bool Add(const unsigned char *inbuf, unsigned long long inlen) = 0;
-   inline bool Add(const char *inbuf, unsigned long long const inlen)
+   virtual bool Add(const unsigned char *inbuf, unsigned long long inlen) APT_NONNULL(2) = 0;
+   inline bool Add(const char *inbuf, unsigned long long const inlen) APT_NONNULL(2)
    { return Add((const unsigned char *)inbuf, inlen); }
 
-   inline bool Add(const unsigned char *Data)
+   inline bool Add(const unsigned char *Data) APT_NONNULL(2)
    { return Add(Data, strlen((const char *)Data)); }
-   inline bool Add(const char *Data)
+   inline bool Add(const char *Data) APT_NONNULL(2)
    { return Add((const unsigned char *)Data, strlen(Data)); }
 
-   inline bool Add(const unsigned char *Beg, const unsigned char *End)
+   inline bool Add(const unsigned char *Beg, const unsigned char *End) APT_NONNULL(2,3)
    { return Add(Beg, End - Beg); }
-   inline bool Add(const char *Beg, const char *End)
+   inline bool Add(const char *Beg, const char *End) APT_NONNULL(2,3)
    { return Add((const unsigned char *)Beg, End - Beg); }
 
    bool AddFD(int Fd, unsigned long long Size = 0);