alpine 3.9
format weakness #9


Weakness Breakdown


A format string exploit occurs when the data of an input string is evaluated as a command by the program. This class of attacks is very similar to buffer overflows since an attacker could execute code, read the stack or cause new behaviors that compromise security. Learn more about format string attacks on OWASP attack index.

Warning code(s):

If format strings can be influenced by an attacker, they can be exploited, and note that sprintf variations do not always 0-terminate.

File Name:



The highlighted line of code below is the trigger point of this particular Alpine 3.9 format weakness.

    struct timeval tv;
    struct timezone tz;
    gettimeofday(&tv, &tz);
    return (tv.tv_sec * 1000) + (long)((double)tv.tv_usec * 0.001);

static const char* TimeStringImplementation()
    time_t tm = time(NULL);
    static char dateTime[80];
    struct tm *tmp = localtime(&tm);
    strftime(dateTime, 80, "%Y-%m-%dT%H:%M:%S", tmp);
    return dateTime;

long (*GetPlatformSpecificTimeInMillis)() = TimeInMillisImplementation;
const char* (*GetPlatformSpecificTimeString)() = TimeStringImplementation;

/* Wish we could add an attribute to the format for discovering mis-use... but the __attribute__(format) seems to not work on va_list */
#ifdef __clang__
#pragma clang diagnostic ignored "-Wformat-nonliteral"

int (*PlatformSpecificVSNprintf)(char *str, size_t size, const char* format, va_list va_args_list) = vsnprintf;

static PlatformSpecificFile PlatformSpecificFOpenImplementation(const char* filename, const char* flag)
   return fopen(filename, flag);

static void PlatformSpecificFPutsImplementation(const char* str, PlatformSpecificFile file)
   fputs(str, (FILE*)file);

static void PlatformSpecificFCloseImplementation(PlatformSpecificFile file)

static void PlatformSpecificFlushImplementation()

PlatformSpecificFile (*PlatformSpecificFOpen)(const char*, const char*) = PlatformSpecificFOpenImplementation;
void (*PlatformSpecificFPuts)(const char*, PlatformSpecificFile) = PlatformSpecificFPutsImplementation;
void (*PlatformSpecificFClose)(PlatformSpecificFile) = PlatformSpecificFCloseImplementation;

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