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libc/resolv: get rid of MD5

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MD5 is used by libc/resolv to generate a random sequence id from a
current time stamp.  Replace this convoluted mechanism with a call
to arc4random().  This permits us to entirely drop MD5 from libc,
simplifying the MD5 rework proposed in D45670.

Approved by:	markj
Reviewed by:	kevans, markj
See also:	D45670
Event:		EuroBSDcon 2025
Differential Revision:	https://reviews.freebsd.org/D52784
This commit is contained in:
Robert Clausecker 2025-09-29 15:53:14 +02:00
parent c16f53782c
commit d518f64cef
6 changed files with 6 additions and 63 deletions
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4
include/resolv.h
View file

@ -188,7 +188,7 @@ struct __res_state {
struct __res_state_ext *ext; /*%< extension for IPv6 */
} _ext;
} _u;
u_char *_rnd; /*%< PRIVATE: random state */
u_char *_rnd; /*%< PRIVATE: random state (unused) */
};
typedef struct __res_state *res_state;
@ -380,7 +380,6 @@ extern const struct res_sym __p_rcode_syms[];
#define res_nisourserver __res_nisourserver
#define res_ownok __res_ownok
#define res_queriesmatch __res_queriesmatch
#define res_rndinit __res_rndinit
#define res_randomid __res_randomid
#define res_nrandomid __res_nrandomid
#define sym_ntop __sym_ntop
@ -445,7 +444,6 @@ int dn_count_labels(const char *);
int dn_comp(const char *, u_char *, int, u_char **, u_char **);
int dn_expand(const u_char *, const u_char *, const u_char *,
char *, int);
void res_rndinit(res_state);
u_int res_randomid(void);
u_int res_nrandomid(res_state);
int res_nameinquery(const char *, int, int, const u_char *,

1
lib/libc/Makefile
View file

@ -109,7 +109,6 @@ NOASM=
.include "${LIBC_SRCTOP}/inet/Makefile.inc"
.include "${LIBC_SRCTOP}/isc/Makefile.inc"
.include "${LIBC_SRCTOP}/locale/Makefile.inc"
.include "${LIBC_SRCTOP}/md/Makefile.inc"
.include "${LIBC_SRCTOP}/nameser/Makefile.inc"
.include "${LIBC_SRCTOP}/net/Makefile.inc"
.include "${LIBC_SRCTOP}/nls/Makefile.inc"

1
lib/libc/include/port_before.h
View file

@ -5,7 +5,6 @@
#define _LIBC 1
#define DO_PTHREADS 1
#define USE_POLL 1
#define HAVE_MD5 1
#define ISC_SOCKLEN_T socklen_t
#define ISC_FORMAT_PRINTF(fmt, args) \

3
lib/libc/md/Makefile.inc
View file

@ -1,3 +0,0 @@
.PATH: ${SRCTOP}/sys/kern
SRCS+= md5c.c

1
lib/libc/resolv/Symbol.map
View file

@ -103,6 +103,5 @@ FBSD_1.0 {
};
FBSD_1.4 {
__res_rndinit;
__res_nrandomid;
};

59
lib/libc/resolv/res_init.c
View file

@ -86,19 +86,6 @@
#include <unistd.h>
#include <netdb.h>
#ifndef HAVE_MD5
# include "../dst/md5.h"
#else
# ifdef SOLARIS2
# include <sys/md5.h>
# elif _LIBC
# include <md5.h>
# endif
#endif
#ifndef _MD5_H_
# define _MD5_H_ 1 /*%< make sure we do not include rsaref md5.h file */
#endif
#include "un-namespace.h"
#include "port_after.h"
@ -184,8 +171,6 @@ __res_vinit(res_state statp, int preinit) {
statp->options = RES_DEFAULT;
}
statp->_rnd = malloc(16);
res_rndinit(statp);
statp->id = res_nrandomid(statp);
memset(u, 0, sizeof(u));
@ -733,48 +718,18 @@ net_mask(struct in_addr in) /*!< XXX - should really use system's version of th
}
#endif
static u_char srnd[16];
void
res_rndinit(res_state statp)
freebsd15_res_rndinit(res_state statp)
{
struct timeval now;
u_int32_t u32;
u_int16_t u16;
u_char *rnd = statp->_rnd == NULL ? srnd : statp->_rnd;
gettimeofday(&now, NULL);
u32 = now.tv_sec;
memcpy(rnd, &u32, 4);
u32 = now.tv_usec;
memcpy(rnd + 4, &u32, 4);
u32 += now.tv_sec;
memcpy(rnd + 8, &u32, 4);
u16 = getpid();
memcpy(rnd + 12, &u16, 2);
(void)statp;
}
__sym_compat(__res_rndinit, freebsd15_res_rndinit, FBSD_1.4);
u_int
res_nrandomid(res_state statp) {
struct timeval now;
u_int16_t u16;
MD5_CTX ctx;
u_char *rnd = statp->_rnd == NULL ? srnd : statp->_rnd;
(void) statp;
gettimeofday(&now, NULL);
u16 = (u_int16_t) (now.tv_sec ^ now.tv_usec);
memcpy(rnd + 14, &u16, 2);
#ifndef HAVE_MD5
MD5_Init(&ctx);
MD5_Update(&ctx, rnd, 16);
MD5_Final(rnd, &ctx);
#else
MD5Init(&ctx);
MD5Update(&ctx, rnd, 16);
MD5Final(rnd, &ctx);
#endif
memcpy(&u16, rnd + 14, 2);
return ((u_int) u16);
return ((u_int)(arc4random() & 0xffff));
}
/*%
@ -808,10 +763,6 @@ res_ndestroy(res_state statp) {
free(statp->_u._ext.ext);
statp->_u._ext.ext = NULL;
}
if (statp->_rnd != NULL) {
free(statp->_rnd);
statp->_rnd = NULL;
}
statp->options &= ~RES_INIT;
}