find the highest version GLIBC_* symbol in a file or directory

glibc-version.c

/* Public Domain code */

/* find the highest version GLIBC_* symbol in a file or directory */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <ctype.h>
#include <elf.h>
#include <fcntl.h>
#include <ftw.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

#define _ELFTYPE(x,n) typedef Elf ## n ## _ ## x  Elf_ ## x
#ifdef __LP64__
#define ELFCLASS_CURRENT ELFCLASS64
#define ELFTYPE(x) _ELFTYPE(x, 64)
#else
#define ELFCLASS_CURRENT ELFCLASS32
#define ELFTYPE(x) _ELFTYPE(x, 32)
#endif

ELFTYPE(Ehdr);
ELFTYPE(Shdr);
ELFTYPE(Sym);
ELFTYPE(Off);


#define PRNT(...)  if (verbose) printf(__VA_ARGS__)

char sym_found[32] = {0};
char path_found[4096] = {0};
int verbose = 0;


const char *lookup_symbol(const char *addr, const size_t fsize)
{
    static char buf[32] = {0};
    char *sym = NULL;

#define CHECK_SIZE(x)  if ((x) >= fsize) return NULL

    /* check magic bytes */
    if (memcmp(addr, ELFMAG, SELFMAG) != 0) {
        return NULL;
    }

    Elf_Ehdr *ehdr = (Elf_Ehdr *)addr;

    /* check size, class and version */
    CHECK_SIZE(ehdr->e_shoff);

    if (ehdr->e_ident[EI_CLASS] != ELFCLASS_CURRENT ||
        ehdr->e_ident[EI_VERSION] != EV_CURRENT)
    {
        return NULL;
    }

    /* section header string table */
    Elf_Shdr *shdr = (Elf_Shdr *)(addr + ehdr->e_shoff);
    Elf_Shdr *sh_strtab = &shdr[ehdr->e_shstrndx];
    CHECK_SIZE(sh_strtab->sh_offset);
    const char *strtab = addr + sh_strtab->sh_offset;
    Elf_Shdr *sh_dynstr = NULL;

    /* iterate through sections to find .dynstr */
    for (size_t i = 0; i < ehdr->e_shnum; i++) {
        CHECK_SIZE(sh_strtab->sh_offset + shdr[i].sh_name);

        if (memcmp(strtab + shdr[i].sh_name, ".dynstr\0", 8) == 0) {
            sh_dynstr = &shdr[i];
            break;
        }
    }

    if (!sh_dynstr) return NULL;

    CHECK_SIZE(sh_dynstr->sh_offset + sh_dynstr->sh_size);
    const char *ptr = addr + sh_dynstr->sh_offset;
    const char *start = ptr;
    const char * const end = ptr + sh_dynstr->sh_size;

    if (*end) return NULL;

    /* parse .dynstr section data for GLIBC_* symbols */
    for ( ; ptr < end; ptr++) {
        if (*ptr) continue;

        if (strncmp(start, "GLIBC_", 6) == 0 &&
            isdigit(start[6]) &&
            (!sym || strverscmp(sym, start) < 0))
        {
            strncpy(buf, start, sizeof(buf)-1);
            sym = buf;
            PRNT("%s  ", sym+6);
        }

        start = ptr + 1;
    }

    return sym;
}

int ftw_callback(const char *fpath, const struct stat *sb, int typeflag, struct FTW *unused)
{
    (void)unused;

    /* check only regular files */
    if (typeflag != FTW_F) return 0;

    if (sb->st_size < (off_t)(sizeof(Elf_Ehdr))) {
        return 0;
    }

    /* open() file */
    int fd = open(fpath, O_RDONLY);
    if (fd < 0) return 0;

    /* mmap() library */
    void *addr = mmap(NULL, sb->st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (addr == MAP_FAILED) {
        perror("mmap()");
        close(fd);
        return 1;
    }

    /* find symbol */
    const char *sym = lookup_symbol((const char *)addr, sb->st_size);

    /* free resources */
    munmap(addr, sb->st_size);
    close(fd);

    if (sym) {
        PRNT("->  %s\n%s\n\n", sym, fpath);
    } else {
        return 0;
    }

    /* compare version strings */
    if (*sym_found == 0 || strverscmp(sym_found, sym) < 0) {
        strncpy(sym_found, sym, sizeof(sym_found)-1);
        strncpy(path_found, fpath, sizeof(path_found)-1);
    }

    return 0;
}

int main(int argc, char **argv)
{
    const char *path = NULL;

    if (argc == 3 && strcmp(argv[1], "-v") == 0) {
        path = argv[2];
        verbose = 1;
    } else if (argc == 2) {
        path = argv[1];
    } else {
        printf("usage: %s [-v] <FILE|DIRECTORY>\n", argv[0]);
        return 1;
    }

    if (nftw(path, ftw_callback, 20, FTW_MOUNT | FTW_PHYS) != 0) {
        perror("nftw()");
        exit(1);
    }

    PRNT("-----------------------------------------\n\n");
    printf("%s\n%s\n", sym_found, path_found);

    return 0;
}

glibc_version2.c

/*	$NetBSD: popen.c,v 1.38 2022/04/19 20:32:15 rillig Exp $	*/

/*	provide popenvp(), a modified version of popenve(3) that uses execvp(3)	*/

/*
 * Copyright (c) 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software written by Ken Arnold and
 * published in UNIX Review, Vol. 6, No. 8.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *	notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *	notice, this list of conditions and the following disclaimer in the
 *	documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *	may be used to endorse or promote products derived from this software
 *	without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define USAGE_TEXT \
	"Use objdump to find the highest GLIBC symbol version in an ELF file.\n\n" \
	"Usage: %s [--use-readelf] <FILE|DIRECTORY>\n"


#ifdef _GNU_SOURCE
#undef _GNU_SOURCE
#endif
#define _GNU_SOURCE

#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <sys/socket.h>

#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <ftw.h>
#include <paths.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

#define FORK_ERROR -1
#define FORK_CHILD  0


static struct pid {
	struct pid *next;
	FILE *fp;
	pid_t pid;
} *pidlist; 


static struct pid *
pdes_get(int *pdes, const char **type)
{
	struct pid *cur;
	int flags = strchr(*type, 'e') ? O_CLOEXEC : 0;
	int serrno;

	if (strchr(*type, '+')) {
		int stype = flags ? (SOCK_STREAM | SOCK_CLOEXEC) : SOCK_STREAM;
		*type = "r+";
		if (socketpair(AF_LOCAL, stype, 0, pdes) < 0)
			return NULL;
	} else  {
		*type = strrchr(*type, 'r') ? "r" : "w";
		if (pipe2(pdes, flags) == -1)
			return NULL;
	}

	if ((cur = malloc(sizeof(*cur))) != NULL)
		return cur;
	serrno = errno;
	(void)close(pdes[0]);
	(void)close(pdes[1]);
	errno = serrno;
	return NULL;
}

static void
pdes_child(int *pdes, const char *type)
{
	struct pid *old;

	/* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
	   from previous popen() calls that remain open in the 
	   parent process are closed in the new child process. */
	for (old = pidlist; old; old = old->next)
		(void)close(fileno(old->fp)); /* don't allow a flush */

	if (type[0] == 'r') {
		(void)close(pdes[0]);
		if (pdes[1] != STDOUT_FILENO) {
			(void)dup2(pdes[1], STDOUT_FILENO);
			(void)close(pdes[1]);
		}
		if (type[1] == '+')
			(void)dup2(STDOUT_FILENO, STDIN_FILENO);
	} else {
		(void)close(pdes[1]);
		if (pdes[0] != STDIN_FILENO) {
			(void)dup2(pdes[0], STDIN_FILENO);
			(void)close(pdes[0]);
		}
	}
}

static void
pdes_parent(int *pdes, struct pid *cur, pid_t pid, const char *type)
{
	FILE *iop;

	/* Parent; assume fdopen can't fail. */
	if (*type == 'r') {
		iop = fdopen(pdes[0], type);
		(void)close(pdes[1]);
	} else {
		iop = fdopen(pdes[1], type);
		(void)close(pdes[0]);
	}

	/* Link into list of file descriptors. */
	cur->fp = iop;
	cur->pid =  pid;
	cur->next = pidlist;
	pidlist = cur;
}

static void
pdes_error(int *pdes, struct pid *cur)
{
	free(cur);
	(void)close(pdes[0]);
	(void)close(pdes[1]);
}

/* modified version of popenve(3) that uses execvp(3) */
FILE *
popenvp(const char *cmd, char *const *argv, const char *type, int disable_child_stderr)
{
	struct pid *cur;
	int pdes[2], serrno;
	pid_t pid;

	if ((cur = pdes_get(pdes, &type)) == NULL)
		return NULL;

	switch (pid = vfork()) {
		case FORK_ERROR:
			serrno = errno;
			pdes_error(pdes, cur);
			errno = serrno;
			return NULL;
			/* NOTREACHED */
		case FORK_CHILD:
			if (disable_child_stderr) {
				close(STDERR_FILENO);
			}
			pdes_child(pdes, type);
			execvp(cmd, argv);
			_exit(127);
			/* NOTREACHED */
	}

	pdes_parent(pdes, cur, pid, type);

	return cur->fp;
}


/******************** end of popen.c ********************/


static int use_readelf = 0;
static char glibc[16] = {0};
static char glibc_file[4096] = {0};

static void strip_glibc_str(char *p)
{
	for ( ; *p != 0; p++) {
		if (isdigit(*p) || *p == '.') {
			continue;
		}

		*p = 0;
		return;
	}
}

static int is_objdump_delim(int c) {
	return isspace(c);
}

static int is_readelf_delim(int c) {
	return (c == '@');
}

const char *glibc_version(const char *file)
{
	int c;
	char buf[24] = {0};
	static char out[16] = {0};

	typedef int (*fptr_t)(int);
	fptr_t is_delim = is_objdump_delim;

	/* set up command line arguments */
	char *argv[] = { "objdump", "--all-headers", (char *)file, NULL };

	if (use_readelf) {
		argv[0] = "readelf";
		argv[1] = "--dyn-syms";
		is_delim = is_readelf_delim;
	}

	/* open pipe */
	FILE *fp = popenvp(argv[0], argv, "re", 1);

	if (!fp) {
		perror("popenvp()");
		return NULL;
	}

	/* get lines */
	while ((c = fgetc(fp)) != EOF) {
		/* check for delimiter */
		if (!is_delim(c) ||
			!fgets(buf, sizeof(buf)-1, fp) ||
			strncmp(buf, "GLIBC_", 6) != 0 ||
			!isdigit(buf[6]))
		{
			continue;
		}

		char *pbuf = buf + 6;
		strip_glibc_str(pbuf);

		if (*out == 0 || strverscmp(out, pbuf) < 0) {
			strcpy(out, pbuf);
		}
	}

	pclose(fp);

	return *out ? out : NULL;
}

static int ftw_callback(const char *fpath, const struct stat *sb, int typeflag, struct FTW *ftwbuf)
{
	(void)sb;
	(void)ftwbuf;

	if (typeflag != FTW_F) {
		return 0;
	}

	const char *p = glibc_version(fpath);

	if (p && (*glibc == 0 || strverscmp(glibc, p) < 0)) {
		strcpy(glibc, p);
		strncpy(glibc_file, fpath, sizeof(glibc_file)-1);
	}

	return 0;
}

int main(int argc, char *argv[])
{
	const char *path;
	char *rp;

	/* parse arguments */
	switch (argc) {
	case 2:
		path = argv[1];
		break;
	case 3:
		if (strcmp(argv[1], "--use-readelf") != 0) {
			fprintf(stderr, USAGE_TEXT, argv[0]);
			return 1;
		}
		use_readelf = 1;
		path = argv[2];
		break;
	default:
		fprintf(stderr, USAGE_TEXT, argv[0]);
		return 1;
	}

	/* resolve path; ntfw() doesn't follow symlinks */
	if ((rp = realpath(path, NULL)) == NULL) {
		perror("realpath()");
		return 1;
	}

	/* call objdump(1) / readelf(1) */
	if (nftw(rp, ftw_callback, 20, FTW_DEPTH | FTW_PHYS) == -1) {
		perror("nftw()");
		free(rp);
		return 1;
	}

	/* print result */
	if (*glibc) {
		printf("%s\nGLIBC_%s\n", glibc_file, glibc);
	}

	free(rp);

	return 0;
}