perm.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or (at
 *   your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Implementation of filed semaphores that release on exit
 *
 * @file src/lib/util/perm.c
 *
 * @copyright 2021 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
RCSID("$Id: 1a431f74bce697b00b0ce7c263da395624d09d30 $")
 
#include <freeradius-devel/util/perm.h>
#include <freeradius-devel/util/strerror.h>
#include <freeradius-devel/util/syserror.h>
 
/** Convert mode_t into humanly readable permissions flags
 *
 * @author Jonathan Leffler.
 *
 * @param mode to convert.
 * @param out Where to write the string to, must be exactly 10 bytes long.
 */
char const *fr_perm_mode_to_str(char out[static 10], mode_t mode)
{
        static char const *rwx[] = {"---", "--x", "-w-", "-wx", "r--", "r-x", "rw-", "rwx"};
 
        strcpy(&out[0], rwx[(mode >> 6) & 0x07]);
        strcpy(&out[3], rwx[(mode >> 3) & 0x07]);
        strcpy(&out[6], rwx[(mode & 7)]);
        if (mode & S_ISUID) out[2] = (mode & 0100) ? 's' : 'S';
        if (mode & S_ISGID) out[5] = (mode & 0010) ? 's' : 'l';
        if (mode & S_ISVTX) out[8] = (mode & 0100) ? 't' : 'T';
        out[9] = '\0';
 
        return out;
}
 
char const *fr_perm_mode_to_oct(char out[static 5], mode_t mode)
{
        out[0] = '0' + ((mode >> 9) & 0x07);
        out[1] = '0' + ((mode >> 6) & 0x07);
        out[2] = '0' + ((mode >> 3) & 0x07);
        out[3] = '0' + (mode & 0x07);
        out[4] = '\0';
 
        return out;
}
 
int fr_perm_mode_from_str(mode_t *out, char const *str)
{
        char const *p;
        mode_t mode;
        int shift;
 
        /*
         *      Octal strings.
         */
        if (*str == '0') {
                unsigned long value;
                char *end = NULL;
 
                /*
                 *      Might as well be quick about it.
                 */
                if (strlen(str) != 4) goto fail;
 
                value = strtoul(str, &end, 8);
                if (*end || (value == ULONG_MAX)) {
                fail:
                        fr_strerror_const("Invalid octal permissions string");
                        return -1;
                }
 
                mode = value;
                goto check;
        }
 
        mode = 0;
        shift = 0;
 
 
        p = str;
 
redo:
        /*
         *      g=foo,u=foo
         */
        if (*p == 'g') {
                if (p[1] != '=') {
                expected_set:
                        fr_strerror_printf("Invalid permission character '%c', expected '='", *p);
                        return -1;
                }
 
                shift = 3;
                p += 2;
 
        } else if (*p == 'u') {
                if (p[1] != '=') goto expected_set;
 
                shift = 0;
                p += 2;
 
        } else if (*p == 'o') {
                if (p[1] != '=') goto expected_set;
 
                shift = 6;
                p += 2;
 
        } /* else 'rwx' is implicitly "u=rwx" */
 
        /*
         *      Parse permissions in any order.
         */
        for (/* nothing */ ; *p != '\0'; p++) {
                mode_t mask = 0;
 
                switch (*p) {
                case 'r':
                        mask = S_IRUSR;
                        break;
 
                case 'w':
                        mask = S_IWUSR;
                        break;
 
                case 'x':
                        mask = S_IXUSR;
                        break;
 
                case ',':
                        p++;
 
                        if (!*p) {
                                fr_strerror_const("Unexpected end of string after ','");
                                return -1;
                        }
 
                        /*
                         *      Alphabetical is OK.
                         */
                        if (isalpha((uint8_t) *p)) goto redo;
 
                        /*
                         *      Non-alphabetical is bad.
                         */
                        FALL_THROUGH;
 
                default:
                        fr_strerror_printf("Invalid permission character '%c', expected one of 'rwx'", *p);
                        return -1;
                }
 
                mask >>= shift;
 
                if ((mode & mask) != 0) {
                        fr_strerror_printf("Permission '%c' is duplicated", *p);
                        return -1;
                }
 
                mode |= mask;
        }
 
check:
        /*
         *      Some attempt at security is a good idea.
         */
        if ((mode & S_IWOTH) != 0) {
                fr_strerror_const("Invalid permissions, files cannot be world writeable");
                return -1;
        }
 
        *out = mode;
        return 0;
}
 
DIAG_OFF(cast-align)
 
/** Resolve a uid to a passwd entry
 *
 * Resolves a uid to a passwd entry. The memory to hold the
 * passwd entry is talloced under ctx, and must be freed when no
 * longer required.
 *
 * @param ctx to allocate passwd entry in.
 * @param out Where to write pointer to entry.
 * @param uid to resolve.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_perm_getpwuid(TALLOC_CTX *ctx, struct passwd **out, uid_t uid)
{
        static size_t len;
        uint8_t *buff;
        int ret;
 
        *out = NULL;
 
        /*
         *      We assume this won't change between calls,
         *      and that the value is the same, so races don't
         *      matter.
         */
        if (len == 0) {
#ifdef _SC_GETPW_R_SIZE_MAX
                long int sc_len;
 
                sc_len = sysconf(_SC_GETPW_R_SIZE_MAX);
                if (sc_len <= 0) sc_len = 1024;
                len = (size_t)sc_len;
#else
                len = 1024;
#endif
        }
 
        buff = talloc_array(ctx, uint8_t, sizeof(struct passwd) + len);
        if (!buff) return -1;
 
        /*
         *      In some cases we may need to dynamically
         *      grow the string buffer.
         */
        while ((ret = getpwuid_r(uid, (struct passwd *)buff, (char *)(buff + sizeof(struct passwd)),
                                 talloc_array_length(buff) - sizeof(struct passwd), out)) == ERANGE) {
                buff = talloc_realloc_size(ctx, buff, talloc_array_length(buff) * 2);
        }
 
        if ((ret != 0) || !*out) {
                fr_strerror_printf("%s", (errno != 0) ? fr_syserror(ret) : "Non-existent user");
                talloc_free(buff);
                errno = ret;
                return -1;
        }
 
        talloc_set_type(buff, struct passwd);
        *out = (struct passwd *)buff;
 
        return 0;
}
 
/** Resolve a username to a passwd entry
 *
 * Resolves a username to a passwd entry. The memory to hold the
 * passwd entry is talloced under ctx, and must be freed when no
 * longer required.
 *
 * @param ctx to allocate passwd entry in.
 * @param out Where to write pointer to entry.
 * @param name to resolve.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_perm_getpwnam(TALLOC_CTX *ctx, struct passwd **out, char const *name)
{
        static size_t len;
        uint8_t *buff;
        int ret;
 
        *out = NULL;
 
        /*
         *      We assume this won't change between calls,
         *      and that the value is the same, so races don't
         *      matter.
         */
        if (len == 0) {
#ifdef _SC_GETPW_R_SIZE_MAX
                long int sc_len;
 
                sc_len = sysconf(_SC_GETPW_R_SIZE_MAX);
                if (sc_len <= 0) sc_len = 1024;
                len = (size_t)sc_len;
#else
                sc_len = 1024;
#endif
        }
 
        buff = talloc_array(ctx, uint8_t, sizeof(struct passwd) + len);
        if (!buff) return -1;
 
        /*
         *      In some cases we may need to dynamically
         *      grow the string buffer.
         */
        while ((ret = getpwnam_r(name, (struct passwd *)buff, (char *)(buff + sizeof(struct passwd)),
                                 talloc_array_length(buff) - sizeof(struct passwd), out)) == ERANGE) {
                buff = talloc_realloc_size(ctx, buff, talloc_array_length(buff) * 2);
        }
 
        if ((ret != 0) || !*out) {
                fr_strerror_printf("%s", (errno != 0) ? fr_syserror(ret) : "Non-existent user");
                talloc_free(buff);
                errno = ret;
                return -1;
        }
 
        talloc_set_type(buff, struct passwd);
        *out = (struct passwd *)buff;
 
        return 0;
}
 
/** Resolve a gid to a group database entry
 *
 * Resolves a gid to a group database entry. The memory to hold the
 * group entry is talloced under ctx, and must be freed when no
 * longer required.
 *
 * @param ctx to allocate passwd entry in.
 * @param out Where to write pointer to entry.
 * @param gid to resolve.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_perm_getgrgid(TALLOC_CTX *ctx, struct group **out, gid_t gid)
{
        static size_t len;
        uint8_t *buff;
        int ret;
 
        *out = NULL;
 
        /*
         *      We assume this won't change between calls,
         *      and that the value is the same, so races don't
         *      matter.
         */
        if (len == 0) {
#ifdef _SC_GETGR_R_SIZE_MAX
                long int sc_len;
 
                sc_len = sysconf(_SC_GETGR_R_SIZE_MAX);
                if (sc_len <= 0) sc_len = 1024;
                len = (size_t)sc_len;
#else
                sc_len = 1024;
#endif
        }
 
        buff = talloc_array(ctx, uint8_t, sizeof(struct group) + len);
        if (!buff) return -1;
 
        /*
         *      In some cases we may need to dynamically
         *      grow the string buffer.
         */
        while ((ret = getgrgid_r(gid, (struct group *)buff, (char *)(buff + sizeof(struct group)),
                                 talloc_array_length(buff) - sizeof(struct group), out)) == ERANGE) {
                buff = talloc_realloc_size(ctx, buff, talloc_array_length(buff) * 2);
        }
 
        if ((ret != 0) || !*out) {
                fr_strerror_printf("%s", (ret != 0) ? fr_syserror(ret) : "Non-existent group");
                talloc_free(buff);
                errno = ret;
                return -1;
        }
 
        talloc_set_type(buff, struct group);
        *out = (struct group *)buff;
 
        return 0;
}
 
/** Resolve a group name to a group database entry
 *
 * Resolves a group name to a group database entry.
 * The memory to hold the group entry is talloced under ctx,
 * and must be freed when no longer required.
 *
 * @param ctx to allocate passwd entry in.
 * @param out Where to write pointer to entry.
 * @param name to resolve.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_perm_getgrnam(TALLOC_CTX *ctx, struct group **out, char const *name)
{
        static size_t len;
        uint8_t *buff;
        int ret;
 
        *out = NULL;
 
        /*
         *      We assume this won't change between calls,
         *      and that the value is the same, so races don't
         *      matter.
         */
        if (len == 0) {
#ifdef _SC_GETGR_R_SIZE_MAX
                long int sc_len;
 
                sc_len = sysconf(_SC_GETGR_R_SIZE_MAX);
                if (sc_len <= 0) sc_len = 1024;
                len = (size_t)sc_len;
#else
                len = 1024;
#endif
        }
 
        buff = talloc_array(ctx, uint8_t, sizeof(struct group) + len);
        if (!buff) return -1;
 
        /*
         *      In some cases we may need to dynamically
         *      grow the string buffer.
         */
        while ((ret = getgrnam_r(name, (struct group *)buff, (char *)(buff + sizeof(struct group)),
                                 talloc_array_length(buff) - sizeof(struct group), out)) == ERANGE) {
                buff = talloc_realloc_size(ctx, buff, talloc_array_length(buff) * 2);
        }
 
        if ((ret != 0) || !*out) {
                fr_strerror_printf("%s", (ret != 0) ? fr_syserror(ret) : "Non-existent group");
                talloc_free(buff);
                errno = ret;
                return -1;
        }
 
        talloc_set_type(buff, struct group);
        *out = (struct group *)buff;
 
        return 0;
}
 
/** Resolve a user name to a GID
 *
 * @param[in] ctx       TALLOC_CTX for temporary allocations.
 * @param[in] out       where to write gid.
 * @param[in] name      of user.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_perm_uid_from_str(TALLOC_CTX *ctx, uid_t *out, char const *name)
{
        int ret;
        struct passwd *result;
 
        ret = fr_perm_getpwnam(ctx, &result, name);
        if (ret < 0) return -1;
 
        *out = result->pw_uid;
        talloc_free(result);
        return 0;
}
 
/** Resolve a group name to a GID
 *
 * @param[in] ctx       TALLOC_CTX for temporary allocations.
 * @param[in] out       where to write gid.
 * @param[in] name      of group.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_perm_gid_from_str(TALLOC_CTX *ctx, gid_t *out, char const *name)
{
        int ret;
        struct group *result;
 
        ret = fr_perm_getgrnam(ctx, &result, name);
        if (ret < 0) return -1;
 
        *out = result->gr_gid;
        talloc_free(result);
        return 0;
}
 
/** Print uid to a string
 *
 * @param ctx TALLOC_CTX for temporary allocations.
 * @param uid to resolve.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
char *fr_perm_uid_to_str(TALLOC_CTX *ctx, uid_t uid)
{
        struct passwd *result;
        char *out;
 
        if (fr_perm_getpwuid(ctx, &result, uid) < 0) return NULL;
        out = talloc_strdup(ctx, result->pw_name);
        talloc_free(result);
 
        return out;
}
 
/** Print gid to a string
 *
 * @param ctx TALLOC_CTX for temporary allocations.
 * @param gid to resolve.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
char *fr_perm_gid_to_str(TALLOC_CTX *ctx, uid_t gid){
        struct group *result;
        char *out;
 
        if (fr_perm_getgrgid(ctx, &result, gid) < 0) return NULL;
        out = talloc_strdup(ctx, result->gr_name);
        talloc_free(result);
 
        return out;
}
 
/** Write a file access error to the fr_strerror buffer, including euid/egid
 *
 * @note retrieve error with fr_strerror()
 *
 * @param num Usually errno, unless the error is returned by the function.
 */
void fr_perm_file_error(int num)
{
        char const      *error;
        struct passwd   *user = NULL;
        struct group    *group = NULL;
 
        error = fr_syserror(num);
 
        if (fr_perm_getpwuid(NULL, &user, geteuid()) < 0) goto finish;
        if (fr_perm_getgrgid(NULL, &group, getegid()) < 0) goto finish;
 
        fr_strerror_printf("Effective user/group - %s:%s: %s", user->pw_name, group->gr_name, error);
finish:
        talloc_free(user);
        talloc_free(group);
}