1 | package net.deterlab.abac; |
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2 | |
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3 | import org.apache.commons.collections15.*; |
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4 | import org.apache.commons.collections15.functors.*; |
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5 | |
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6 | import edu.uci.ics.jung.graph.*; |
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7 | import edu.uci.ics.jung.graph.event.*; |
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8 | import edu.uci.ics.jung.graph.util.*; |
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9 | |
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10 | import java.awt.geom.Point2D; |
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11 | import java.io.*; |
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12 | import java.util.*; |
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13 | |
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14 | /** |
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15 | * Represents a global graph of credentials in the form of principals and |
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16 | * attributes. |
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17 | */ |
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18 | public class CredentialGraph { |
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19 | protected Graph<Role,Credential> g = null; |
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20 | protected java.util.Set<Credential> derived_edges = new HashSet<Credential>(); |
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21 | protected Query pq; |
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22 | protected boolean m_dirty; |
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23 | |
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24 | public CredentialGraph() { |
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25 | /* create the graph */ |
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26 | g = Graphs.<Role,Credential>synchronizedDirectedGraph( |
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27 | new DirectedSparseGraph<Role,Credential>()); |
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28 | pq = new Query(g); |
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29 | } |
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30 | |
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31 | /** |
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32 | * Returns a Query object which can be used to query the graph. This object |
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33 | * becomes invalid if the graph is modified. |
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34 | */ |
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35 | public Query querier() { |
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36 | derive_implied_edges(); |
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37 | return new Query(g); |
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38 | } |
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39 | |
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40 | /** |
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41 | * Add a credential to the graph. |
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42 | */ |
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43 | public void add_credential(Credential cred) { |
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44 | Role tail = cred.tail(); |
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45 | Role head = cred.head(); |
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46 | |
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47 | /* explicitly add the vertices, otherwise get a null pointer exception */ |
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48 | g.addVertex(tail); |
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49 | g.addVertex(head); |
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50 | |
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51 | g.addEdge(cred, tail, head); |
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52 | |
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53 | // add the prereqs of an intersection to the graph |
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54 | if (tail.is_intersection()) |
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55 | for (Role prereq : tail.prereqs()) |
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56 | g.addVertex(prereq); |
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57 | |
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58 | m_dirty = true; |
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59 | } |
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60 | |
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61 | /** |
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62 | * Remove a credential from the graph. |
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63 | */ |
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64 | public void remove_credential(Credential cred) { |
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65 | if (g.containsEdge(cred)) |
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66 | g.removeEdge(cred); |
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67 | m_dirty = true; |
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68 | } |
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69 | |
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70 | /** |
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71 | * Returns a collection of the credentials in the graph. |
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72 | */ |
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73 | public Collection<Credential> credentials() { |
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74 | Collection<Credential> creds = new HashSet<Credential>(); |
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75 | |
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76 | // only return creds with a cert: all others are derived edges |
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77 | for (Credential cred : g.getEdges()) |
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78 | if (cred.cert() != null) |
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79 | creds.add(cred); |
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80 | |
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81 | return creds; |
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82 | } |
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83 | |
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84 | /** |
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85 | * Derive the implied edges in the graph, according to RT0 derivation rules. |
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86 | * They are added to this graph. See "Distributed Credential Chain Discovery |
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87 | * in Trust Management" by Ninghui Li et al. for details. Note that a |
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88 | * derived linking edge can imply a new intersection edge and vice versa. |
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89 | * Therefore we iteratively derive edges, giving up when an iteration |
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90 | * produces 0 new edges. |
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91 | */ |
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92 | protected synchronized void derive_implied_edges() { |
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93 | // nothing to do on a clean graph |
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94 | if (!m_dirty) |
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95 | return; |
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96 | |
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97 | clear_old_edges(); |
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98 | |
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99 | // iteratively derive links. continue as long as new links are added |
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100 | while (derive_links_iter() > 0) |
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101 | ; |
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102 | m_dirty = false; |
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103 | } |
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104 | |
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105 | /** |
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106 | * Single iteration of deriving implied edges. Returns the number of new |
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107 | * links added. |
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108 | */ |
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109 | protected int derive_links_iter() { |
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110 | int count = 0; |
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111 | |
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112 | /* for every node in the graph.. */ |
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113 | for (Role vertex : g.getVertices()) { |
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114 | if (vertex.is_intersection()) { |
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115 | // for each prereq edge: |
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116 | // find set of principals that have the prereq |
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117 | // find the intersection of all sets (i.e., principals that satisfy all prereqs) |
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118 | // for each principal in intersection: |
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119 | // add derived edge |
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120 | |
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121 | Set<Role> principals = null; |
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122 | |
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123 | for (Role prereq : vertex.prereqs()) { |
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124 | Set<Role> cur_principals = pq.find_principals(prereq); |
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125 | |
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126 | if (principals == null) |
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127 | principals = cur_principals; |
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128 | else |
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129 | // no, they couldn't just call it "intersection" |
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130 | principals.retainAll(cur_principals); |
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131 | |
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132 | if (principals.size() == 0) |
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133 | break; |
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134 | } |
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135 | |
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136 | // add em |
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137 | for (Role principal : principals) |
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138 | if (add_derived_edge(vertex, principal)) |
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139 | ++count; |
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140 | } |
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141 | |
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142 | else if (vertex.is_linking()) { |
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143 | // make the rest of the code a bit clearer |
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144 | Role A_r1_r2 = vertex; |
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145 | |
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146 | Role A_r1 = new Role(A_r1_r2.A_r1()); |
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147 | String r2 = A_r1_r2.r2(); |
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148 | |
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149 | /* locate the node A.r1 */ |
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150 | if (!g.containsVertex(A_r1)) continue; /* boring: nothing of the form A.r1 */ |
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151 | |
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152 | /* for each B that satisfies A_r1 */ |
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153 | for (Role principal : pq.find_principals(A_r1)) { |
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154 | Role B_r2 = new Role(principal + "." + r2); |
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155 | if (!g.containsVertex(B_r2)) continue; |
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156 | |
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157 | if (add_derived_edge(A_r1_r2, B_r2)) |
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158 | ++count; |
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159 | } |
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160 | } |
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161 | } |
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162 | |
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163 | return count; |
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164 | } |
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165 | |
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166 | /** |
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167 | * Add a derived edge in the graph. Returns true only if the edge does not |
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168 | * exist. |
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169 | */ |
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170 | protected boolean add_derived_edge(Role head, Role tail) { |
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171 | // edge exists: return false |
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172 | if (g.findEdge(tail, head) != null) |
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173 | return false; |
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174 | |
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175 | // add the new edge |
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176 | Credential derived_edge = new Credential(head, tail); |
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177 | derived_edges.add(derived_edge); |
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178 | g.addEdge(derived_edge, tail, head); |
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179 | |
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180 | return true; |
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181 | } |
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182 | |
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183 | /** |
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184 | * Clear the derived edges that currently exist in the graph. This is done |
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185 | * before the edges are rederived. The derived edges in filtered graphs are |
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186 | * also cleared. |
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187 | */ |
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188 | protected void clear_old_edges() { |
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189 | for (Credential i: derived_edges) |
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190 | g.removeEdge(i); |
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191 | derived_edges = new HashSet<Credential>(); |
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192 | } |
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193 | } |
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