be-gssapi-common.c

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/*-------------------------------------------------------------------------
 *
 * be-gssapi-common.c
 *     Common code for GSSAPI authentication and encryption
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *       src/backend/libpq/be-gssapi-common.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "libpq/be-gssapi-common.h"
 
/*
 * Fetch all errors of a specific type and append to "s" (buffer of size len).
 * If we obtain more than one string, separate them with spaces.
 * Call once for GSS_CODE and once for MECH_CODE.
 */
static void
pg_GSS_error_int(char *s, size_t len, OM_uint32 stat, int type)
{
    gss_buffer_desc gmsg;
    size_t      i = 0;
    OM_uint32   lmin_s,
                msg_ctx = 0;
 
    do
    {
        if (gss_display_status(&lmin_s, stat, type, GSS_C_NO_OID,
                               &msg_ctx, &gmsg) != GSS_S_COMPLETE)
            break;
        if (i > 0)
        {
            if (i < len)
                s[i] = ' ';
            i++;
        }
        if (i < len)
            memcpy(s + i, gmsg.value, Min(len - i, gmsg.length));
        i += gmsg.length;
        gss_release_buffer(&lmin_s, &gmsg);
    }
    while (msg_ctx);
 
    /* add nul termination */
    if (i < len)
        s[i] = '\0';
    else
    {
        elog(COMMERROR, "incomplete GSS error report");
        s[len - 1] = '\0';
    }
}
 
/*
 * Report the GSSAPI error described by maj_stat/min_stat.
 *
 * errmsg should be an already-translated primary error message.
 * The GSSAPI info is appended as errdetail.
 *
 * The error is always reported with elevel COMMERROR; we daren't try to
 * send it to the client, as that'd likely lead to infinite recursion
 * when elog.c tries to write to the client.
 *
 * To avoid memory allocation, total error size is capped (at 128 bytes for
 * each of major and minor).  No known mechanisms will produce error messages
 * beyond this cap.
 */
void
pg_GSS_error(const char *errmsg,
             OM_uint32 maj_stat, OM_uint32 min_stat)
{
    char        msg_major[128],
                msg_minor[128];
 
    /* Fetch major status message */
    pg_GSS_error_int(msg_major, sizeof(msg_major), maj_stat, GSS_C_GSS_CODE);
 
    /* Fetch mechanism minor status message */
    pg_GSS_error_int(msg_minor, sizeof(msg_minor), min_stat, GSS_C_MECH_CODE);
 
    /*
     * errmsg_internal, since translation of the first part must be done
     * before calling this function anyway.
     */
    ereport(COMMERROR,
            (errmsg_internal("%s", errmsg),
             errdetail_internal("%s: %s", msg_major, msg_minor)));
}
 
/*
 * Store the credentials passed in into the memory cache for later usage.
 *
 * This allows credentials to be delegated to us for us to use to connect
 * to other systems with, using, e.g. postgres_fdw or dblink.
 */
#define GSS_MEMORY_CACHE "MEMORY:"
void
pg_store_delegated_credential(gss_cred_id_t cred)
{
    OM_uint32   major,
                minor;
    gss_OID_set mech;
    gss_cred_usage_t usage;
    gss_key_value_element_desc cc;
    gss_key_value_set_desc ccset;
 
    cc.key = "ccache";
    cc.value = GSS_MEMORY_CACHE;
    ccset.count = 1;
    ccset.elements = &cc;
 
    /* Make the delegated credential only available to current process */
    major = gss_store_cred_into(&minor,
                                cred,
                                GSS_C_INITIATE, /* credential only used for
                                                 * starting libpq connection */
                                GSS_C_NULL_OID, /* store all */
                                true,   /* overwrite */
                                true,   /* make default */
                                &ccset,
                                &mech,
                                &usage);
 
    if (major != GSS_S_COMPLETE)
    {
        pg_GSS_error("gss_store_cred", major, minor);
    }
 
    /* Credential stored, so we can release our credential handle. */
    major = gss_release_cred(&minor, &cred);
    if (major != GSS_S_COMPLETE)
    {
        pg_GSS_error("gss_release_cred", major, minor);
    }
 
    /*
     * Set KRB5CCNAME for this backend, so that later calls to
     * gss_acquire_cred will find the delegated credentials we stored.
     */
    setenv("KRB5CCNAME", GSS_MEMORY_CACHE, 1);
}