diff --git a/sessreg/sessreg.c b/sessreg/sessreg.c index cfe7e86..3dc2992 100644 --- a/sessreg/sessreg.c +++ b/sessreg/sessreg.c @@ -93,18 +93,6 @@ static void set_utmpx (struct utmpx *u, const char *line, const char *user, const char *host, Time_t date, int addp); #endif -#ifdef SYSV -/* used for hashing ut_id */ -typedef unsigned long int ub4; /* unsigned 4-byte quantities */ -typedef unsigned char ub1; /* unsigned 1-byte quantities */ - -#define hashsize(n) ((ub4)1<<(n)) -#define hashmask(n) (hashsize(n)-1) - -ub4 hash(register ub1 *k, register ub4 length, register ub4 initval); - -#endif - static int wflag, uflag, lflag; static char *wtmp_file, *utmp_file, *line; #ifdef USE_UTMPX @@ -416,23 +404,21 @@ set_utmp (struct utmp *u, char *line, char *user, char *host, Time_t date, int a bzero (u->ut_name, sizeof (u->ut_name)); #ifdef SYSV if (line) { + int i; /* - * The ut_id is 4 bytes long. We make a hash of the line - * received, preceding it by ":" to prevent clashing with - * other ut_ids. + * this is a bit crufty, but + * follows the apparent conventions in + * the ttys file. ut_id is only 4 bytes + * long, and the last 4 bytes of the line + * name are written into it, left justified. */ - ub4 h; - u->ut_id[0]=':'; - h = hash(line, strlen(line),0x9e3779b9); - h = (h & hashmask((sizeof(u->ut_id)-sizeof(char))*8)); - (void) strncpy (u->ut_id + 1,(char *) &h, sizeof (u->ut_id)-sizeof(char)); + i = strlen (line); + if (i >= sizeof (u->ut_id)) + i -= sizeof (u->ut_id); + else + i = 0; + (void) strncpy (u->ut_id, line + i, sizeof (u->ut_id)); } else - /* - * From utmp(5): - * Clearing ut_id may result in race conditions leading to corrupted - * utmp entries and and potential security holes. - */ - /* TODO: CHECK this */ bzero (u->ut_id, sizeof (u->ut_id)); if (addp) { u->ut_pid = getppid (); @@ -676,129 +662,3 @@ findslot (char *line_name, char *host_name, int addp, int slot) return freeslot; } #endif - -#ifdef SYSV -/* --------------------------------------------------------------------- -mix -- mix 3 32-bit values reversibly. -For every delta with one or two bits set, and the deltas of all three - high bits or all three low bits, whether the original value of a,b,c - is almost all zero or is uniformly distributed, -* If mix() is run forward or backward, at least 32 bits in a,b,c - have at least 1/4 probability of changing. -* If mix() is run forward, every bit of c will change between 1/3 and - 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.) -mix() was built out of 36 single-cycle latency instructions in a - structure that could supported 2x parallelism, like so: - a -= b; - a -= c; x = (c>>13); - b -= c; a ^= x; - b -= a; x = (a<<8); - c -= a; b ^= x; - c -= b; x = (b>>13); - ... - Unfortunately, superscalar Pentiums and Sparcs can't take advantage - of that parallelism. They've also turned some of those single-cycle - latency instructions into multi-cycle latency instructions. Still, - this is the fastest good hash I could find. There were about 2^^68 - to choose from. I only looked at a billion or so. --------------------------------------------------------------------- -*/ -#define mix(a,b,c) \ -{ \ - a -= b; a -= c; a ^= (c>>13); \ - b -= c; b -= a; b ^= (a<<8); \ - c -= a; c -= b; c ^= (b>>13); \ - a -= b; a -= c; a ^= (c>>12); \ - b -= c; b -= a; b ^= (a<<16); \ - c -= a; c -= b; c ^= (b>>5); \ - a -= b; a -= c; a ^= (c>>3); \ - b -= c; b -= a; b ^= (a<<10); \ - c -= a; c -= b; c ^= (b>>15); \ -} - -/* --------------------------------------------------------------------- -hash() -- hash a variable-length key into a 32-bit value - k : the key (the unaligned variable-length array of bytes) - len : the length of the key, counting by bytes - initval : can be any 4-byte value -Returns a 32-bit value. Every bit of the key affects every bit of -the return value. Every 1-bit and 2-bit delta achieves avalanche. -About 6*len+35 instructions. - -The best hash table sizes are powers of 2. There is no need to do -mod a prime (mod is sooo slow!). If you need less than 32 bits, -use a bitmask. For example, if you need only 10 bits, do - h = (h & hashmask(10)); -In which case, the hash table should have hashsize(10) elements. - -If you are hashing n strings (ub1 **)k, do it like this: - for (i=0, h=0; i - Date: Thu, 27 May 2004 22:33:06 -0700 - To: Margarita Manterola - Subject: Re: Hash function - - The algorithm is public domain. I ask that I be referenced as the - source of the algorithm, but I can't enforce that, since being public - domain means I've reserved no rights at all. - --- Branden Robinson, 2004-06-06] - -See http://burtleburtle.net/bob/hash/evahash.html -Use for hash table lookup, or anything where one collision in 2^^32 is -acceptable. Do NOT use for cryptographic purposes. --------------------------------------------------------------------- -*/ - -ub4 -hash(register ub1 *k, register ub4 length, register ub4 initval) -{ - register ub4 a,b,c,len; - - /* Set up the internal state */ - len = length; - a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */ - c = initval; /* the previous hash value */ - - /*---------------------------------------- handle most of the key */ - while (len >= 12) - { - a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24)); - b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24)); - c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24)); - mix(a,b,c); - k += 12; len -= 12; - } - - /*------------------------------------- handle the last 11 bytes */ - c += length; - switch(len) /* all the case statements fall through */ - { - case 11: c+=((ub4)k[10]<<24); - case 10: c+=((ub4)k[9]<<16); - case 9 : c+=((ub4)k[8]<<8); - /* the first byte of c is reserved for the length */ - case 8 : b+=((ub4)k[7]<<24); - case 7 : b+=((ub4)k[6]<<16); - case 6 : b+=((ub4)k[5]<<8); - case 5 : b+=k[4]; - case 4 : a+=((ub4)k[3]<<24); - case 3 : a+=((ub4)k[2]<<16); - case 2 : a+=((ub4)k[1]<<8); - case 1 : a+=k[0]; - /* case 0: nothing left to add */ - } - mix(a,b,c); - /*-------------------------------------------- report the result */ - return c; -} - -#endif